Questo lavoro è stato supportato dalla Fondazione nazionale di scienze naturali della Cina (21471037), Guangdong scienza naturale fondi per illustri giovani studiosi (15ZK0307), scienza e tecnologia pianificazione progetto della provincia di Guangdong (2017A050506051) e la Consiglio di sovvenzioni di ricerca del HKSAR [GRF 11303414].

Attenzione: Si prega di consultare tutte le schede di sicurezza rilevanti prima dell'uso. Metil thiomethoxide disolfuro e sodio sono fortemente maleodorante e deve essere gestita in una cappa aspirante. Sodio metallico è altamente reattivo e richiede speciali misure di sicurezza contro il rischio incendio e rischi di esplosione. Oltre all'uso di una cappa aspirante, dispositivi di protezione individuale (occhiali di sicurezza, guanti, camice da laboratorio, pieno lunghezza pantaloni e scarpe chiuse) dovrebbero essere impiegati correttamente. Porzioni delle seguenti procedure coinvolgono standard, tecniche di gestione privo di aria.
1. preparazione di sodio Thiomethoxide (CH3SNa)
<ol><li>Collegare un pallone di Schlenk 200 mL ad un collettore di gasolio sotto vuoto. Evacuare il pallone e poi backfill con N2 tre volte, tale che il pallone è riempito con una pressione di2 N leggermente positiva. Nota: Un metodo simile di preparazione CH3SNa è stato accennato nella letteratura, ma nessun procedure dettagliate sono state fornite27,28.</li>
	<li>Prendere un blocco di sodio metallico da serbatoio dell'olio di cherosene. Utilizzare una carta assorbente per togliere l'olio residuo sulla superficie e usare un coltello per togliere lo strato di ossido sulla superficie. Tagliare rapidamente 6,7 g di sodio metallico (0,29 mol) in piccoli pezzi (ad es., circa dimensioni di soia) e trasferire immediatamente i piccoli pezzi nel matraccio Schlenk 200 mL sotto un flusso di contatore di N2. Tappare con un setto immediatamente. Nota: Per ridurre l'esposizione all'aria, uno può tagliare fuori il sodio con qualche variazione della quantità di 6,7 g e regolare la quantità di THF e dimetil disolfuro secondo la quantità effettiva di sodio usato.</li>
	<li>Trasferimento 80 mL di un THF anidro, senz'aria nella boccetta tramite cannula sotto protezione2 N dalla linea di Schlenk. Prelevare mL 14,0 di solfuro dimetilico (0,158 talpe; pre-eliminato l'inceppo con N2) in una siringa e iniettarla nel pallone goccia a goccia sotto la protezione di2 N. Attenzione: Solfuro dimetilico è maleodorante e deve essere gestita in una cappa aspirante.</li>
	<li>Sostituire il setto con un tappo di vetro smerigliato. Mescolare la miscela di reazione a temperatura ambiente per 24 h e poi a 60 ° C per 3 h. Nota: La miscela di reazione è diventato viscosa sotto agitazione a temperatura ambiente; Quando riscaldato fino a 60 ° C, la miscela può essere mescolata in modo più semplice e quindi accelerare la reazione verso completamento.</li>
	<li>Con la temperatura è mantenuta a circa 60 ° C, utilizzare un flusso di N2 (0,2 L/min) per soffiare fuori la maggior parte del solvente THF e il disolfuro di dimetil in eccesso, finché non viene visualizzato un solido asciutto. Utilizzare una trappola a freddo (ad es., ghiaccio secco/acetone) per raccogliere il THF e dimetil disolfuro nel deflusso.</li>
	<li>Evacuare il restante miscela solida con un olio pompa per circa 2 h rimuovere il residuo di THF e dimetil disolfuro e poi backfill con N2 per ottenere un solido di colore giallo chiaro (19,8 g, 97%). Conservare il prodotto solido CH3SNa in un'atmosfera di azoto al buio. Nota: Per proteggere la pompa dell'olio di vuoto, una trappola a freddo deve essere usata durante il pompaggio.</li>
</ol>2. preparazione del 2,3,6,7,10,11-hexoctaedri (pentanoylthio) triphenylene (HVaTT) come un linker tiolo protetta
<ol><li>Caricare 0,664 g di CH3SNa (9.0 mmol) in un matraccio Schlenk 50 mL sotto un flusso di contatore di N2 (cioè., collegato come sopra ad un collettore di aspirazione gas sotto protezione2 N). Nota: CH3SNa è sensibile all'aria e assorbe facilmente l'acqua. Per ridurre al minimo l'esposizione all'aria, uno può pesare rapidamente un importo specifico e aggiungerlo al pallone e quindi regolare di conseguenza la quantità di altro reagente, 2,3,6,7,10,11-hexabromotriphenylene (HBT). Attenzione: Solido CH3SNa ha un odore forte e deve essere gestita in una cappa aspirante.</li>
	<li>Aggiungere 0,216 g di HBT (0,30 mmol) al pallone sotto un flusso di contatore di N2e sigillo la beuta con un setto.</li>
	<li>Trasferire 10 mL di anidro e airless 1,3-dimetil-2-imidazolidinone (DMEU) nel pallone tramite cannula sotto protezione2 N dalla linea di Schlenk.</li>
	<li>Sostituire il setto con un tappo di vetro normale e mescolare la miscela di reazione e utilizzare un bagno di sale per riscaldare fino a 240 ° C per 48 h N.2.</li>
	<li>TLC monitoraggio dello stato di avanzamento della reazione: N.2, utilizzare un contagocce di vetro per prelevare una piccola aliquota della miscela di reazione (circa 0,1 mL) e iniettare immediatamente in un campione di liquido pulito di cloruro di valeroil (circa 0,1 mL) in una plastica microcentrifuga flaconcino e poi agitare per 1 min; la miscela dovrebbe girare subito a torbida con un colore grigio-bianco. Aggiungere 0,4 mL di acqua deionizzata e 0,1 mL di acetato di etile, chiudere il tappo e agitare per pochi secondi. Nota: Se la reazione è stata già completata, ci non sarà tutto ciò che appare tra gli strati di acqua e acetato di etile. In caso contrario, una sostanza insolubile bianca apparirà tra i due strati.</li>
	<li>Dispensare fuori la parte superiore e usarlo per avvistare i piatti di TLC. Utilizzare 1:4 etere di acetato di etile/petrolio per sviluppare la lastra TLC. Per una reazione completa, la molecola bersaglio si presenta come un normale posto intorno Rf = 0,4 sotto una lampada UV.</li>
	<li>Spegnere il riscaldamento e prendere il pallone di reazione fuori il bagno di sale a raffreddare a temperatura ambiente e quindi utilizzare un bagno di ghiaccio per raffreddare il pallone fino a 0 ° C.</li>
	<li>Iniettare 1,5 mL di cloruro di valeroil (12,6 mmol) nel pallone goccia a goccia (per un periodo di circa 2 min) con una siringa in N2. Continuate a mescolare a 0 ° C per 2 h. Nota: l'aggiunta di cloruro di valeroil lentamente e a bassa temperatura aiuta a ridurre la generazione di sottoprodotti.</li>
	<li>Versare il composto in 50 mL di acqua ghiacciata ed estratto utilizzando acetato di etile (3 30 mL). Quindi lavare lo strato organico combinato con acqua (6 60 mL), asciugare sopra anidro MgSO4e rimuovere le sostanze volatili da un evaporatore rotante.</li>
	<li>Isolare il prodotto grezzo oleoso da cromatografia a colonna utilizzando 01:10 etere di acetato di etile/petrolio come eluente, che offre un prodotto oleoso giallo-chiaro dopo rotativo evaporazione dei solventi. Utilizzare 1:4 etere di acetato di etile/petrolio per sviluppare la piastra di TLC, Rf = 0,4. Purificare ulteriormente il prodotto oleoso mediante il passaggio di triturazione qui sotto.</li>
	<li>Aggiungere 5 mL di methanolto il prodotto oleoso e Sonicare per 2 min. raccogliere il solido biancastro risultante mediante aspirazione filtrazione (resa: 59%).</li>
</ol>3. preparazione dei monocristalli del materiale quadro HTT-Pb
<ol><li>Mescolare 11,4 mg di PbOAc·3H2O (0.030 mmol) in 1,0 mL di diammina dell'etilene in un flaconcino per rendere una soluzione chiara.</li>
	<li>Caricare 9,1 mg di HVaTT (0.010 mmol), 2,0 mL di metanolo pre-degassato soluzione di NaOH (70 mmol/L) e 1,0 mL della diammina dell'etilene in una fiala di 10mL vuota e Sonicare per 5 min.</li>
	<li>Aggiungere la soluzione di PbOAc alla miscela lisati mediante HVaTT. Poi la bolla la miscela di reazione con N2 per 1 min e messo sul tappo a vite per sigillare il flaconcino.</li>
	<li>Riscaldare il flacone a 90 ° C in un forno per 48 h, seguito da raffreddamento naturale a temperatura ambiente, durante la quale giallo-arancio, ottaedrici monocristalli adatti per studi di diffrazione di raggi x del singolo-cristallo si formarono (resa: 45%).</li>
	<li>Aspirazione filtrazione fuori i cristalli e lavare rapidamente con MeOH. Trasferire i cristalli con un contagocce di vetro in una fiala contenente airless MeOH (5ml) per stoccaggio a temperatura ambiente.</li>
</ol>4. interazione di Paraquat Diiodide con cristalli HTT-Pb
<ol><li>Utilizzare un pipetta Pasteur di vetro per ritirare alcuni grani di cristallo singolo HTT-Pb dello stock di MeOH e rilasciarlo in una capsula Petri (diametro 35 mm e profondità 10 mm). Assorbire il liquido di metanolo di tessuto o carta da filtro (o lasciare che il MeOH asciugare naturalmente) e poi cadere i cristalli di poche gocce di una soluzione acquosa di paraquat diiodide (0,1%, w/w).</li>
	<li>Osservare il colore cambiamento dei cristalli dall'occhio o sotto un microscopio.</li>
</ol>

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K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Room-temperature+acetylene+hydration+by+a+Hg(II)-laced+metal-organic+framework.">Room-temperature acetylene hydration by a Hg(II)-laced metal-organic framework.</a> Chem Commun. 51 (54), 10941-10944 (2015).</li><li>Gui, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tackling+poison+and+leach:+catalysis+by+dangling+thiol-palladium+functions+within+a+porous+metal-organic+solid.">Tackling poison and leach: catalysis by dangling thiol-palladium functions within a porous metal-organic solid.</a> Chem Commun. 51 (32), 6917-6920 (2015).</li><li>He, J., Zeller, M., Hunter, A. D., Xu, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+shakeup+of+metal-organic+frameworks:+the+rise+of+the+sidekick.">Functional shakeup of metal-organic frameworks: the rise of the sidekick.</a> CrystEngComm. 17 (48), 9254-9263 (2015).</li></ol>

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La reazione tra il gruppo di bromo e l'anione thiomethoxide apparentemente prodotto in primo luogo il thioether di metile, che poi è stato demetilato dalla thiomethoxide in eccesso per fornire il prodotto di thiolate anione. Per garantire la completa conversione per l'anione tiolico desiderata (soprattutto per un substrato di PBDE come HBT), le condizioni vigorose di prolungato riscaldamento (ad es., 240 ° C oltre 48 h) con un grande eccesso di sodio thiomethoxide (ad esempio, più di tre volte le tal...

C'è attualmente di grande interesse nell'impiegare forte, polarizzabile metallo-zolfo (ad es., metallo-tiolico) collegamenti per la costruzione di aprono materiali struttura con elettrocatalitica avanzata e proprietà conduttive1,2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10. oltre a promuovere l'interazione elettronica e trasporto nello stato esteso, i legami metallo-zolfo morbidi e covalenti anche impartire la migliore stabilità per applicazioni in ambienti acquosi. Tra i blocchi di costruzione attrezzata zolfo, simmetrici, multidentate policiclici aromatici elementi costitutivi come 2,3,6,7,10,11-triphenylene hexathiol (HTT)9,11,12,13 , 14 non solo fornitura altamente polarizzabili π-elettroni, ma anche offrire vantaggi distinti rispetto alla progettazione della struttura e sintesi. In primo luogo, il nucleo triphenylene rigida e simmetrica, in collaborazione con i gruppi dithiolene chelante di HTT, serve per bloccare in ioni metallici in motivi regolari incollaggio, semplificando la previsione strutturale della futura rete7, 15. insieme alla geometria rigida e aperta del linker zolfo, strutture di framework con caratteristiche di porosità sostanziale possono essere realizzate spesso allo stato solido.
Una grande sfida in assemblaggio di materiali del tiolo-attrezzata metallo orangic framework (MOF) è radicata nella sintesi delle molecole organiche del linker. In un protocollo di classico, il gruppo tioalcool doveva essere derivato dal gruppo di fenolo utilizzando il riarrangiamento di Newman-Kwart del O- aril fenossiacetico precursore16,17,18. Questo approccio, tuttavia, comporta passaggi elaborati preparative per la molecola del precursore di fenolo come pure le complicazioni potenziali di una trasformazione di fase solida ad alta temperatura. Un altro modo di fare i tioli utilizza riduttiva dealchilazione di tioeteri sotto le dure condizioni di, ad esempio, il sodio metallico in ammoniaca liquida19,20,21,22e non è compatibile con il carbossile e molte altre funzioni di donatore per la costruzione della rete.
In confronto, il protocollo presentato qui ha molteplici vantaggi: sicurezza, comodità, convenienza e compatibilità con altri gruppi funzionali (ad es., carbonitrile e pyridinyl). Riscaldando con vigore l'alogenuro aromatico generalmente poco costoso (ad es., hexabromotriphenylene) e thiomethoxide anione, l'anione thiolate è stato generato (tramite il prodotto intermedio metile thioether) e quindi acilato per dare la stalla e facile da maneggiare tioesteri prodotto-tutto in una pentola.
Descriveremo inoltre una procedura per utilizzando le molecole di tioesteri come forma mascherata del linker di tiolo per accedere a una rete di metallo-dithiolene singolo-cristallino semiconduttore e poroso. A differenza i tioli autoportante altamente reattivi, che tendono a decomporsi e complicare la cristallizzazione di metallo-tiolico open frameworks, il tioestere può essere prontamente spaccati (ad es., di NaOH o etilendiammina) in situ per fornire il specie tiolo, che serve a mitigare la reazione tra le unità di mercaptano e i centri di metallo e di conseguenza migliorare la cristallizzazione.
Questo protocollo di preparazione del tiolo/tioestere non ampiamente utilizzato da altri gruppi per il campo emergente dei quadri di metallo-zolfo, anche se dealkylations nucleofila di tioeteri arilici alchilici di anioni tiolico già sono stati ben documentati di organico chimici23,24,25,26. Proponendo questo efficiente metodo sintetico per tioesteri e loro uso per facilitare la cristallizzazione delle reti di metallo-zolfo, desideriamo promuovere ulteriori sforzi per colmare il divario intellettuale e pratico tra chimica organica sintetica e chimica dello stato solido, in modo da aiutare lo sviluppo veloce e sano dei quadri porosi.

<table border="0" cellpadding="0" cellspacing="0" width="850">
	<tbody>
		<tr height="22">
			<td height="22" style="height:22px;width:216px;">Bromine</td>
			<td style="width:348px;">DAMAO CHEMICAL REAGENT FACTORY</td>
			<td style="width:119px;">7726-95-6</td>
			<td style="width:167px;">Highly toxic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Triphenylene&#160;&#160;</td>
			<td style="width:348px;">HWRK Chem</td>
			<td style="width:119px;">HWG45510</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Iron powder</td>
			<td style="width:348px;">Sigma-Aldrich</td>
			<td style="width:119px;">12310</td>
			<td></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:216px;">Nitrobenzene</td>
			<td style="width:348px;">DAMAO CHEMICAL REAGENT FACTORY</td>
			<td style="width:119px;">2934</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:216px;">Diethyl ether&#160;</td>
			<td style="width:348px;">DAMAO CHEMICAL REAGENT FACTORY</td>
			<td style="width:119px;">48</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:216px;">Dichloromethane</td>
			<td style="width:348px;">DAMAO CHEMICAL REAGENT FACTORY</td>
			<td>3067</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Sodium metal</td>
			<td style="width:348px;">J&#38;K</td>
			<td style="width:119px;">WM-NMS-54-25X-50G</td>
			<td>Air sensitive</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Tetrahydrofuran</td>
			<td style="width:348px;">J&#38;K</td>
			<td style="width:119px;">315353</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Dimethyl disulfide</td>
			<td style="width:348px;">INTERNATIONAL LABORATORY USA</td>
			<td style="width:119px;">726415</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">1,3-Dimethyl-2-imadazolidinone</td>
			<td style="width:348px;">J&#38;K</td>
			<td style="width:119px;">50483</td>
			<td>Dried over 4&#197; sieves</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Valeryl&#160; chloride</td>
			<td style="width:348px;">J&#38;K</td>
			<td style="width:119px;">99590</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Methanol</td>
			<td style="width:348px;">Guangzhou Chemical Reagent Factory</td>
			<td>2334</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sodium hydroxide</td>
			<td style="width:348px;">Guangzhou Chemical Reagent Factory</td>
			<td style="width:119px;">1588</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ethylene diamine</td>
			<td style="width:348px;">Riedel-de Ha&#235;n</td>
			<td style="width:119px;">15070</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Lead acetate trihydrate</td>
			<td>PEKING CHEMICAL WORKE</td>
			<td style="width:119px;">861218</td>
			<td></td>
		</tr>
	</tbody>
</table>

synthesis of a thiol building block for the crystallization of a semiconducting gyroidal metal-sulfur framework

Presentiamo un metodo per la preparazione di molecole tioesteri come forma mascherata del linker del tiolo e loro utilizzo per l'accesso a una rete di metallo-dithiolene semiconduttori e poroso allo stato cristallino singola altamente ordinata. A differenza i tioli autoportante altamente reattivi, che tendono a decomporsi e complicare la cristallizzazione di metallo-tiolico open frameworks, il tioestere reagisce in situ per fornire le specie tiolo, che serve a mitigare la reazione tra il unità di mercaptano e i centri di metallo e migliorare di conseguenza la cristallizzazione. In particolare, il tioestere è stato sintetizzato in una routine di uno-pentola: un aromatico bromuro (hexabromotriphenylene) ha reagito con eccesso di sodio thiomethoxide condizioni vigoroso per formare prima il prodotto intermedio thioether. Il thioether era quindi demetilato dalla thiomethoxide in eccesso per fornire l'anione tiolico che era acilato per formare il prodotto tioesteri. Il tioestere convenientemente è stato purificato mediante cromatografia su colonna standard e quindi utilizzato direttamente nella sintesi quadro, in cui NaOH ed etilendiammina servono a ripristinare in situ il tioestere al linker di tiolo per il montaggio del singolo-cristallino Pb (II)-dithiolene rete. Rispetto ad altri metodi per la sintesi del tiolo (ad es., fendendo alchil thioether utilizzando sodio metallo e liquido ammoniaca), la sintesi di tioesteri qui utilizza condizioni semplici e reagenti economici. Inoltre, il prodotto di tioestere è stabile e può essere comodamente gestiti e archiviati. Ancora più importante, in contrasto con la difficoltà generica di accesso cristallina metallo-tiolico aperto quadri, dimostriamo che usando il tioestere per in situ formazione del linker tiolo migliora notevolmente la cristallinità della a stato solido prodotto. Abbiamo intenzione di incoraggiare gli sforzi di ricerca più ampi sulle strutture metallo-zolfo tecnologicamente importante divulgando il protocollo sintetico per i tioesteri, nonché il quadro cristallino solido.

Lo spettro IR della molecola HVaTT (raccolto con il metodo di pellet di KBr) presenta suo assorbimento più forte alle 1.700 cm-1, in conformità con l'allungamento del carbonilico del gruppo tioestere funzionale. 1H-NMR lo spettro di HVaTT (400 MHz, CDCl3) rivela un singoletto a δ 8,47 da atomi di idrogeno aromatici, insieme a 4 multipletti da protoni alifatici: δ 8,47 (s, 6 H, CHAr), 2,75-2.72 (t, J = 7.4, 12 H, CH2), 1.81-1.77 (m, ...

Watch this Scientific Journal Video about Synthesis of a Thiol Building Block for the Crystallization of a Semiconducting Gyroidal Metal-sulfur Framework at JoVE.com

Synthesis of a Thiol Building Block for the Crystallization of a Semiconducting Gyroidal Metal-sulfur Framework

Qui, presentiamo una sintesi one-pot, transizione-metallo-libera dei tioli e tioesteri da alogenuri aromatici e thiomethoxide di sodio, seguita dalla preparazione dei monocristalli di una rete di metallo-dithiolene utilizzando specie tiolo generato in situ dal tioestere più stabile e trattabili.

Sintesi di un tiolo Building Block per la cristallizzazione di un quadro di Gyroidal metallo-zolfo ossidi semiconduttori

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and ...

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Ethers, Epoxides, Sulfides

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8.9K Views.  Guangdong University of Technology. Qui, presentiamo una sintesi one-pot, transizione-metallo-libera dei tioli e tioesteri da alogenuri aromatici e thiomethoxide di sodio, seguita dalla preparazione dei monocristalli di una rete di metallo-dithiolene utilizzando specie tiolo generato in situ dal tioestere più stabile e trattabili.

Video: Synthesis of a Thiol Building Block for the Crystallization of a Semiconducting Gyroidal Metal-sulfur Framework

Preparation and Use of Samarium Diiodide (SmI2) in Organic Synthesis: The Mechanistic Role of HMPA and Ni(II) Salts in the Samarium Barbier Reaction

Although initially considered an esoteric reagent, SmI2 has become a common tool for synthetic organic chemists. SmI2 is generated through the addition of molecular iodine to samarium metal in THF.1,2-3 It is a mild and selective single electron reductant and its versatility is a result of its ability to initiate a wide range of reductions including C-C bond-forming and cascade or sequential reactions. SmI2 can reduce a variety of functional groups including sulfoxides and sulfones, phosphine oxides, epoxides, alkyl and aryl halides, carbonyls, and conjugated double bonds.2-12 One of the fascinating features of SmI-2-mediated reactions is the ability to manipulate the outcome of reactions through the selective use of cosolvents or additives. In most instances, additives are essential in controlling the rate of reduction and the chemo- or stereoselectivity of reactions.13-14 Additives commonly utilized to fine tune the reactivity of SmI2 can be classified into three major groups: (1) Lewis bases (HMPA, other electron-donor ligands, chelating ethers, etc.), (2) proton sources (alcohols, water etc.), and (3) inorganic additives (Ni(acac)2, FeCl3, etc).3
Understanding the mechanism of SmI2 reactions and the role of the additives enables utilization of the full potential of the reagent in organic synthesis. The Sm-Barbier reaction is chosen to illustrate the synthetic importance and mechanistic role of two common additives: HMPA and Ni(II) in this reaction. The Sm-Barbier reaction is similar to the traditional Grignard reaction with the only difference being that the alkyl halide, carbonyl, and Sm reductant are mixed simultaneously in one pot.1,15 Examples of Sm-mediated Barbier reactions with a range of coupling partners have been reported,1,3,7,10,12 and have been utilized in key steps of the synthesis of large natural products.16,17 Previous studies on the effect of additives on SmI2 reactions have shown that HMPA enhances the reduction potential of SmI2 by coordinating to the samarium metal center, producing a more powerful,13-14,18 sterically encumbered reductant19-21 and in some cases playing an integral role in post electron-transfer steps facilitating subsequent bond-forming events.22 In the Sm-Barbier reaction, HMPA has been shown to additionally activate the alkyl halide by forming a complex in a pre-equilibrium step.23
Ni(II) salts are a catalytic additive used frequently in Sm-mediated transformations.24-27 Though critical for success, the mechanistic role of Ni(II) was not known in these reactions. Recently it has been shown that SmI2 reduces Ni(II) to Ni(0), and the reaction is then carried out through organometallic Ni(0) chemistry.28
These mechanistic studies highlight that although the same Barbier product is obtained, the use of different additives in the SmI2 reaction drastically alters the mechanistic pathway of the reaction. The protocol for running these SmI2-initiated reactions is described.

Preparation and Use of Samarium Diiodide SmI2 in Organic Synthesis: The Mechanistic Role of HMPA and NiII Salts in the Samarium Barbier Reaction

A straightforward procedure for the preparation of samarium diiodide (SmI2) in THF is described. The role of two main additives namely hexamethylphosphoramide (HMPA) and Ni(acac)2 in Sm mediated reactions is demonstrated in the Sm-Barbier reaction.

Preparazione ed uso di samario diioduro (SMI<sub&gt; 2</sub&gt;) Nella sintesi organica: il ruolo meccanicistico di HMPA e Ni (II) sali nella reazione Samario Barbier

Although initially considered an esoteric reagent, SmI2 has become a common tool for synthetic organic chemists. SmI2 is generated through the addition of ...

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Synthesis and Purification of Iodoaziridines Involving Quantitative Selection of the Optimal Stationary Phase for Chromatography

The highly diastereoselective preparation of cis-N-Ts-iodoaziridines through reaction of diiodomethyllithium with N-Ts aldimines is described. Diiodomethyllithium is prepared by the deprotonation of diiodomethane with LiHMDS, in a THF/diethyl ether mixture, at -78 &#176;C in the dark. These conditions are essential for the stability of the LiCHI2 reagent generated. The subsequent dropwise addition of N-Ts aldimines to the preformed diiodomethyllithium solution affords an amino-diiodide intermediate, which is not isolated. Rapid warming of the reaction mixture to 0 &#176;C promotes cyclization to afford iodoaziridines with exclusive cis-diastereoselectivity. The addition and cyclization stages of the reaction are mediated in one reaction flask by careful temperature control.
Due to the sensitivity of the iodoaziridines to purification, assessment of suitable methods of purification is required. A protocol to assess the stability of sensitive compounds to stationary phases for column chromatography is described. This method is suitable to apply to new iodoaziridines, or other potentially sensitive novel compounds. Consequently this method may find application in range of synthetic projects. The procedure involves firstly the assessment of the reaction yield, prior to purification, by 1H NMR spectroscopy with comparison to an internal standard. Portions of impure product mixture are then exposed to slurries of various stationary phases appropriate for chromatography, in a solvent system suitable as the eluent in flash chromatography. After stirring for 30 min to mimic chromatography, followed by filtering, the samples are analyzed by 1H NMR spectroscopy. Calculated yields for each stationary phase are then compared to that initially obtained from the crude reaction mixture. The results obtained provide a quantitative assessment of the stability of the compound to the different stationary phases; hence the optimal can be selected. The choice of basic alumina, modified to activity IV, as a suitable stationary phase has allowed isolation of certain iodoaziridines in excellent yield and purity.

A protocol for the diastereoselective one-pot preparation of cis-N-Ts-iodoaziridines is described. The generation of diiodomethyllithium, addition to N-Ts aldimines and cyclization of the amino gem-diiodide intermediate to iodoaziridines is demonstrated. Also included is a protocol to rapidly and quantitatively assess the most appropriate stationary phase for purification by chromatography.

Sintesi e purificazione di Iodoaziridines Coinvolgere quantitativa Selezione del Ottimale fase stazionaria per cromatografia

The highly diastereoselective preparation of cis-N-Ts-iodoaziridines through reaction of diiodomethyllithium with N-Ts aldimines is described. ...

Synthesis and Exfoliation of Discotic Zirconium Phosphates to Obtain Colloidal Liquid Crystals

Due to their abundance in natural clay and potential applications in advanced materials, discotic nanoparticles are of interest to scientists and engineers. Growth of such anisotropic nanocrystals through a simple chemical method is a challenging task. In this study, we fabricate discotic nanodisks of zirconium phosphate [Zr(HPO4)2&#183;H2O] as a model material using hydrothermal, reflux and microwave-assisted methods. Growth of crystals is controlled by duration time, temperature, and concentration of reacting species. The novelty of the adopted methods is that discotic crystals of size ranging from hundred nanometers to few micrometers can be obtained while keeping the polydispersity well within control. The layered discotic crystals are converted to monolayers by exfoliation with tetra-(n)-butyl ammonium hydroxide [(C4H9)4NOH, TBAOH]. Exfoliated disks show isotropic and nematic liquid crystal phases. Size and polydispersity of disk suspensions is highly important in deciding their phase behavior.

A two dimensional model material of discotic zirconium phosphate was developed. The inorganic crystal with lamellar structure was synthesized by hydrothermal, reflux, and microwave-assisted methods. On exfoliation with organic molecules, layered crystals can be converted to monolayers, and nematic liquid crystal phase was formed at sufficient concentration of monolayers.

Sintesi ed esfoliazione della discotici zirconio Fosfati di ottenere cristalli liquidi colloidale

Due to their abundance in natural clay and potential applications in advanced materials, discotic nanoparticles are of interest to scientists and ...

Synthesis of Programmable Main-chain Liquid-crystalline Elastomers Using a Two-stage Thiol-acrylate Reaction

This study presents a novel two-stage thiol-acrylate Michael addition-photopolymerization (TAMAP) reaction to prepare main-chain liquid-crystalline elastomers (LCEs) with facile control over network structure and programming of an aligned monodomain. Tailored LCE networks were synthesized using routine mixing of commercially available starting materials and pouring monomer solutions into molds to cure. An initial polydomain LCE network is formed via a self-limiting thiol-acrylate Michael-addition reaction. Strain-to-failure and glass transition behavior were investigated as a function of crosslinking monomer, pentaerythritol tetrakis(3-mercaptopropionate) (PETMP). An example non-stoichiometric system of 15 mol% PETMP thiol groups and an excess of 15 mol% acrylate groups was used to demonstrate the robust nature of the material. The LCE formed an aligned and transparent monodomain when stretched, with a maximum failure strain over 600%. Stretched LCE samples were able to demonstrate both stress-driven thermal actuation when held under a constant bias stress or the shape-memory effect when stretched and unloaded. A permanently programmed monodomain was achieved via a second-stage photopolymerization reaction of the excess acrylate groups when the sample was in the stretched state. LCE samples were photo-cured and programmed at 100%, 200%, 300%, and 400% strain, with all samples demonstrating over 90% shape fixity when unloaded. The magnitude of total stress-free actuation increased from 35% to 115% with increased programming strain. Overall, the two-stage TAMAP methodology is presented as a powerful tool to prepare main-chain LCE systems and explore structure-property-performance relationships in these fascinating stimuli-sensitive materials.

A novel methodology is presented to synthesize and program main-chain liquid-crystalline elastomers using commercially available starting monomers. A wide range of thermomechanical properties was tailored by adjusting the amount of crosslinker, while the actuation performance was dependent on the amount of applied strain during programming.

Sintesi di programmabile principale catena Elastomeri liquido-cristallini Utilizzando una a due stadi Thiol-acrilato di reazione

This study presents a novel two-stage thiol-acrylate Michael addition-photopolymerization (TAMAP) reaction to prepare main-chain liquid-crystalline ...

Synthesis of Cd-free InP/ZnS Quantum Dots Suitable for Biomedical Applications

Fluorescent nanocrystals, specifically quantum dots, have been a useful tool for many biomedical applications. For successful use in biological systems, quantum dots should be highly fluorescent and small/monodisperse in size. While commonly used cadmium-based quantum dots possess these qualities, they are potentially toxic due to the possible release of Cd2+ ions through nanoparticle degradation. Indium-based quantum dots, specifically InP/ZnS, have recently been explored as a viable alternative to cadmium-based quantum dots due to their relatively similar fluorescence characteristics and size. The synthesis presented here uses standard hot-injection techniques for effective nanoparticle growth; however, nanoparticle properties such as size, emission wavelength, and emission intensity can drastically change due to small changes in the reaction conditions. Therefore, reaction conditions such temperature, reaction duration, and precursor concentration should be maintained precisely to yield reproducible products. Because quantum dots are not inherently soluble in aqueous solutions, they must also undergo surface modification to impart solubility in water. In this protocol, an amphiphilic polymer is used to interact with both hydrophobic ligands on the quantum dot surface and bulk solvent water molecules. Here, a detailed protocol is provided for the synthesis of highly fluorescent InP/ZnS quantum dots that are suitable for use in biomedical applications.

In this protocol, the synthesis of Cd-free InP/ZnS quantum dots (QDs) is detailed. InP-based QDs are gaining popularity due to the toxicity of Cd2+ ions that may be released through nanoparticle degradation. After synthesis, QDs are solubilized in water using an amphiphilic polymer for use in biomedical applications.

Sintesi di Cd-libera InP / ZnS Quantum Dots adatto per applicazioni biomediche

Fluorescent nanocrystals, specifically quantum dots, have been a useful tool for many biomedical applications. For successful use in biological systems, ...

HKUST-1 as a Heterogeneous Catalyst for the Synthesis of Vanillin

Vanillin (4-hydoxy-3-methoxybenzaldehyde) is the main component of the extract of vanilla bean. The natural vanilla scent is a mixture of approximately 200 different odorant compounds in addition to vanillin. The natural extraction of vanillin (from the orchid Vanilla planifolia, Vanilla tahitiensis and Vanilla pompon) represents only 1% of the worldwide production and since this process is expensive and very long, the rest of the production of vanillin is synthesized. Many biotechnological approaches can be used for the synthesis of vanillin from lignin, phenolic stilbenes, isoeugenol, eugenol, guaicol, etc., with the disadvantage of harming the environment since these processes use strong oxidizing agents and toxic solvents. Thus, eco-friendly alternatives on the production of vanillin are very desirable and thus, under current investigation. Porous coordination polymers (PCPs) are a new class of highly crystalline materials that recently have been used for catalysis. HKUST-1 (Cu3(BTC)2(H2O)3, BTC = 1,3,5-benzene-tricarboxylate) is a very well known PCP which has been extensively studied as a heterogeneous catalyst. Here, we report a synthetic strategy for the production of vanillin by the oxidation of trans-ferulic acid using HKUST-1 as a catalyst.

The conversion of trans-ferulic acid to vanillin was achieved by heterogeneous catalysis. HKUST-1 was employed in this synthesis and the essential step in the catalytic process was the generation of unsaturated metal sites. Thus, when the catalyst was activated under vacuum, full vanillin conversion (yield of 95%) was obtained.

HKUST-1 come catalizzatore eterogeneo per la sintesi di vanillina

Vanillin (4-hydoxy-3-methoxybenzaldehyde) is the main component of the extract of vanilla bean. The natural vanilla scent is a mixture of approximately ...

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the development of antibody drug conjugates (ADCs) and nanomedicine, fluorescent microscopy and systems chemistry. For many of these applications, specificity of the bioconjugation method used is of prime concern. The Michael addition of maleimides with cysteine(s) on the target proteins is highly selective and proceeds rapidly under mild conditions, making it one of the most popular methods for protein bioconjugation.
We demonstrate here the modification of the only surface-accessible cysteine residue on yeast cytochrome c with a ruthenium(II) bisterpyridine maleimide. The protein bioconjugation is verified by gel electrophoresis and purified by aqueous-based fast protein liquid chromatography in 27% yield of isolated protein material. Structural characterization with MALDI-TOF MS and UV-Vis is then used to verify that the bioconjugation is successful. The protocol shown here is easily applicable to other cysteine - maleimide coupling of proteins to other proteins, dyes, drugs or polymers.

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

This protocol details the important steps required for the bioconjugation of a cysteine containing protein to a maleimide, including reagent purification, reaction conditions, bioconjugate purification and bioconjugate characterization.

Sintesi di proteine ​​bioconiugati<em&gt; via</em&gt; Chimica cisteina-maleimmide

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the ...

Sulfate Separation by Selective Crystallization with a Bis-iminoguanidinium Ligand

A simple and effective method for selective sulfate separation from aqueous solutions by crystallization with a bis-guanidinium ligand, 1,4-benzene-bis(iminoguanidinium) (BBIG), is demonstrated. The ligand is synthesized as the chloride salt (BBIG-Cl) by in situ imine condensation of terephthalaldehyde with aminoguanidinium chloride in water, followed by crystallization as the sulfate salt (BBIG-SO4). Alternatively, BBIG-Cl is synthesized ex situ in larger scale from ethanol. The sulfate separation ability of the BBIG ligand is demonstrated by selective and quantitative crystallization of sulfate from seawater. The ligand can be recycled by neutralization of BBIG-SO4 with aqueous NaOH and crystallization of the neutral bis-iminoguanidine, which can be converted back into BBIG-Cl with aqueous HCl and reused in another separation cycle. Finally, 35S-labeled sulfate and &#946; liquid scintillation counting are employed for monitoring the sulfate concentration in solution. Overall, this protocol will instruct the user in the necessary skills to synthesize a ligand, employ it in the selective crystallization of sulfate from aqueous solutions, and quantify the separation efficiency.

A protocol for in situ aqueous synthesis of a bis(iminoguanidinium) ligand and its utilization in selective separation of sulfate is presented.

Separazione solfato da selettiva cristallizzazione con un legante bis-iminoguanidinium

A simple and effective method for selective sulfate separation from aqueous solutions by crystallization with a bis-guanidinium ligand, ...

Electrophoretic Crystallization of Ultrathin High-performance Metal-organic Framework Membranes

We report the synthesis of thin, highly intergrown, polycrystalline metal-organic framework (MOF) membranes on a wide range of unmodified porous and non-porous supports (polymer, ceramic, metal, carbon, and graphene). We developed a novel crystallization technique, which is termed the ENACT approach: the electrophoretic nuclei assembly for the crystallization of highly intergrown thin films (ENACT). This approach allows for a high density of heterogeneous nucleation of MOFs on a chosen substrate via the electrophoretic deposition (EPD) directly from the precursor sol. The growth of well-packed MOF nuclei leads to a highly intergrown polycrystalline MOF film. We show that this simple approach can be used for the synthesis of thin, intergrown zeolite imidazole framework (ZIF)-7 and ZIF-8 films. The resulting 500 nm-thick ZIF-8 membranes show a considerably high H2 permeance (8.3 x 10-6 mol m-2 s-1 Pa-1) and ideal gas selectivities (7.3 for H2/CO2, 15.5 for H2/N2, 16.2 for H2/CH4, and 2655 for H2/C3H8). An attractive performance for C3H6/C3H8 separation is also achieved (a C3H6 permeance of 9.9 x 10-8 mol m-2 s-1 Pa-1 and a C3H6/C3H8 ideal selectivity of 31.6 at 25 &#176;C). Overall, the ENACT process, owing to its simplicity, can be extended to synthesize intergrown thin films of a wide range of nanoporous crystalline materials.

A simple, reproducible, and versatile approach for the synthesis of intergrown, polycrystalline metal-organic framework membranes on a wide range of unmodified porous and non-porous supports is presented.

Elettroforetica cristallizzazione delle membrane ultrasottile ad alte prestazioni Metal-organic frameworks

We report the synthesis of thin, highly intergrown, polycrystalline metal-organic framework (MOF) membranes on a wide range of unmodified porous and ...

Solid-phase Synthesis of [4.4] Spirocyclic Oximes

A convenient synthetic route for spirocyclic heterocycles is well sought after due to the molecule&#39;s potential use in biological systems. By means of solid-phase synthesis, regenerating Michael (REM) linker strategies, and 1,3-dipolar cycloaddition, a library of structurally similar heterocycles, both with and without a spirocyclic center, can be constructed. The main advantages of the solid-support synthesis are as follows: first, each reaction step can be driven to completion using a large excess of reagents resulting in high yields; next, the use of commercially available starting materials and reagents keep the costs low; finally, the reaction steps are easy to purify via simple filtration. The REM linker strategy is attractive because of its recyclability and traceless nature. Once a reaction scheme is completed, the linker can be reused multiple times. In a typical solid-phase synthesis, the product contains either a part of or the whole linker, which can prove undesirable. The REM linker is &#34;traceless&#34; and the point of attachment between the product and the polymer is indistinguishable. The high diastereoselectivity of the intramolecular 1,3-dipolar cycloaddition is well documented. Limited by the insolubility of the solid support, the reaction progression can only be monitored by a change in the functional groups (if any) via infrared (IR) spectroscopy. Thus, the structural identification of intermediates cannot be characterized by conventional nuclear magnetic resonance (NMR) spectroscopy. Other limitations to this method stem from the compatibilities of the polymer/linker to the desired chemical reaction scheme. Herein we report a protocol that allows for the convenient production of spirocyclic heterocycles that, with simple modifications, can be automated with high-throughput techniques.

Here we present a protocol to demonstrate an efficient method for the synthesis of spirocyclic heterocycles. The five-step process utilizes solid-phase synthesis and regenerating Michael linker strategies. Generally difficult to synthesize, we present a customizable method for the synthesis of spirocyclic molecules otherwise inaccessible to other modern approaches.

Sintesi in fase solida di [4,4] Spirocyclic ossime

A convenient synthetic route for spirocyclic heterocycles is well sought after due to the molecule&#39;s potential use in biological systems. By means of ...