Gli autori ringraziano Deutsche Forschungsgemeinschaft, Bayer Pharma AG, Chemtura Organometallics GmbH Bergkamen, Bayer Services GmbH, BASF AG e Sasol GmbH per il sostegno finanziario.

1. Preparazione di titanio (IV) Soluzione tert -butoxide/Triethylchlorosilane <ol><li> Sciogliere 400 mg (400 microlitri) di titanio (IV) tert-butossido (1 mmol) in 10 ml di diclorometano anidro. Aggiungere 150 mg (170 microlitri) trietilclorosilano (1 mmol) di questa soluzione a temperatura ambiente. 1 ml di questa soluzione contiene diclorometano-0.1 mmol titanio (IV) e terz-butossido 0,1 mmol trietilclorosilano. </li></ol> 2. Pinacol-reazione Tetraphenyl-1 ,2-etandiolo (1) con 2-Ethylbutyraldehyde <ol><li> Risolvere 366 mg di tetrafenil-1 ,2-etandiolo (1, 1 mmol) e 300 mg (370 ml) di distillato fresco 2-ethylbutyraldehyde (3 mmol) in 3 ml di diclorometano anidro. </li><li> Aggiungere 0,5 ml di titanio preparato separatamente (IV) tert -butoxide/triethylchlorosilane soluzione (0,05 mmol). </li><li> Agitare la miscela risultante a temperatura ambiente in un tubo di reazione sigillato. </li><li> Confirm la reazione è completa mediante cromatografia su strato sottile (eluente: esano / acetone - 9/1) su gel di silice piastre TLC (60 F254). La fine della reazione viene raggiunta al momento tetrafenil-1 ,2-etandiolo 1 non può più essere rilevato (~ 12 ore). Il Rf valore del prodotto è di 0,3 14. </li><li> Diluire la miscela di reazione risultante con 50 ml di diclorometano. </li><li> Lavare la miscela di reazione diluita successivamente con 20 ml di cloruro di ammonio acquoso saturo e soluzione di bicarbonato di sodio in un imbuto separatore. </li><li> Isolare lo strato organico da un imbuto separatore. </li><li> Asciugare lo strato organico agitando su solfato di magnesio secco. </li><li> Filtrare la sospensione da un filtro di carta a pieghe e raccogliere i filtrati. </li><li> Rimuovere diclorometano dal filtrato sotto vuoto a 40 ° C mediante un evaporatore rotativo (10-30 mmHg). Evaporazione di solventi richiederà 20 min. </li><li> Purificare il residuo rimanentemediante colonna cromatografia flash su colonna di gel di silice (0,035-0,070 mm, ACROS) con un gradiente di esano / acetone (partendo da 19:1 a 16:04 scendendo) per acquisire 280 mg di 1,2-diolo 2f (0,99 mmol). </li><li> Confermare l&#39;identità del 2f 1,2-diolo da 1 H spettroscopia di risonanza magnetica nucleare (NMR) usando CDCl 3 come solvente. Per uno spettrometro NMR 300 MHz, il 1 H NMR del diolo è la seguente: δ = 0,78 (t, 3H, J = 7.4 Hz), 0.87 (t, 3H, J = 7.3 Hz), 1,18-1,40 (m , 4H), 1,75-1,81 (m, 1H), 1.91 (s, 1H, OH), 3.12 (s, 1H, OH), 4.68 (d, 1H, J = 1.2 Hz), 7,19-7,37 (m, 6H ), 7,44-7,46 (m, 2H), 7,61-7,63 (m, 2H). </li></ol> 3. Pinacol-reazione Tetraphenyl-1 ,2-ethanediol (1) con dietilchetone <ol><li> Risolvere 366 mg di tetrafenil-1 ,2-etandiolo (1, 1 mmol) e 345 mg (423 microlitri) di etere chetone (4 mmoli) in 3mL di diclorometano secco. </li><li> Aggiungere 1 ml di titanio preparato separatamente (IV) soluzione -butoxide/triethylchloro-silane terz (0,1 mmol). </li><li> Agitare la miscela risultante a temperatura ambiente in un tubo di reazione sigillato. </li><li> Conferma la reazione è completa mediante cromatografia su strato sottile (eluente: esano / acetone, 9,1) su piastre di gel di silice 60 F254 (TLC). La fine della reazione viene raggiunta al tempo, quando tetrafenil-1 ,2-etandiolo 1 non può essere rilevato (~ 12 ore). La Rf del prodotto è 0,3 14. </li><li> Diluire la miscela di reazione risultante con 50 ml di diclorometano. </li><li> Lavare la miscela di reazione diluita successivamente con 20 ml di cloruro di ammonio acquoso saturo e soluzione di carbonato di sodio in un imbuto separatore. </li><li> Isolare lo strato organico da un imbuto separatore. </li><li> Asciugare lo strato organico agitando su solfato di magnesio secco. </li><li> Filtrare la sospensione da un documento fil scanalatater e raccogliere i filtrati. </li><li> Rimuovere diclorometano sotto vuoto a 40 ° C mediante un evaporatore rotativo (10-30 mmHg). L&#39;evaporazione di sostanze volatili richiederà 30 min. </li><li> Purificare il residuo residuo mediante cromatografia flash su colonna attraverso una colonna di gel di silice (0,035-0,070 mm, ACROS) con un gradiente di esano / acetone (partendo da 19:1 a 16:04 scendendo) per acquisire 250 mg di 1, 2-diolo 4f (0,93 mmol). </li><li> Confermare l&#39;identità del prodotto da 1 H spettroscopia di risonanza magnetica nucleare (NMR) usando CDCl 3 come solvente. Per un spettrometro NMR 300 MHz, il 1 H NMR del 4f diolo è la seguente: δ = 0.92 (t, 6H, J = 7.6 Hz), 1.78 (m, 4H), 2.03 (s, 1H, OH), 2.83 (s, 1H, OH), 7,26-7,35 (m, 6H), 7,69-7,71 (m, 4H). </li></ol>

<ol>
	<li>Hirao, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Catalytic+reductive+coupling+of+carbonyl+compounds+-+The+pinacol+coupling+reaction+and.">Catalytic reductive coupling of carbonyl compounds - The pinacol coupling reaction and.</a> 279, 53-75 (2007).</li><li>Chatterjee, A., Joshi, N. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evolution+of+the+stereoselective+pinacol+coupling+reaction.">Evolution of the stereoselective pinacol coupling reaction.</a> Tetrahedron. 62, 12137-12158 (2006).</li><li>Ladipo, F. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Low-valent+titanium-mediated+reductive+coupling+of+carbonyl+compounds.">Low-valent titanium-mediated reductive coupling of carbonyl compounds.</a> Curr. Org. Chem. 10, 965-980 (2006).</li><li>Gans&#228;uer, A., Bluhm, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reagent-controlled+transition-metal-catalyzed+radical+reactions.">Reagent-controlled transition-metal-catalyzed radical reactions.</a> Chem. Rev. 100, 2771-2788 (2000).</li><li>Duan, X. -. F., Feng, J. X., Zi, G. -. F., Zhang, Z. -. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Convenient+synthesis+of+unsymmetrical+pinacols+by+coupling+of+structurally+similar+aromatic+aldehydes+mediated+by+low-valent+titanium.">A Convenient synthesis of unsymmetrical pinacols by coupling of structurally similar aromatic aldehydes mediated by low-valent titanium.</a> Synthesis. , 277-282 (2009).</li><li>Paquette, L. A., Lai, K. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pinacol+macrocyclization-based+route+to+the+polyfused+medium-sized+CDE+ring+system+of+lancifodilactone.">Pinacol macrocyclization-based route to the polyfused medium-sized CDE ring system of lancifodilactone.</a> G. Org. Lett. 10, 3781-3784 (2008).</li><li>Maekawa, H., Yamamoto, Y., Shimada, H., Yonemura, K., Nishiguchi, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mg-+promoted+mixed+pinacol+coupling.">Mg- promoted mixed pinacol coupling.</a> Tetrahedron Lett. 45, 3869-3872 (2004).</li><li>Kang, M., Park, J., Pedersen, S. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pinacol+cross+coupling+reactions+of+ethyl+2-alkyl-2-formylpropionates.+stereoselective+synthesis+of+2,2,4-+trialkyl-3-hydroxy-&#947;-butyrolactones.">Pinacol cross coupling reactions of ethyl 2-alkyl-2-formylpropionates. stereoselective synthesis of 2,2,4- trialkyl-3-hydroxy-&#947;-butyrolactones.</a> Syn. Lett. , 41-43 (1997).</li><li>Askham, F. R., Carroll, K. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anionic+zirconaoxiranes+as+nucleophilic+aldehyde+equivalents.+application+to+intermolecular+pinacol+cross+coupling.">Anionic zirconaoxiranes as nucleophilic aldehyde equivalents. application to intermolecular pinacol cross coupling.</a> J. Org. Chem. 58, 7328-7329 (1993).</li><li>Hou, Z., Takamine, K., Aoki, O., Shiraishi, H., Fujiwara, Y., Taniguchi, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nucleophilic+Addition+of+lanthanoid+metal+umpoled+diaryl+ketones+to+electrophiles.">Nucleophilic Addition of lanthanoid metal umpoled diaryl ketones to electrophiles.</a> J. Org. Chem. 53, 6077-6084 (1988).</li><li>Groth, U., Jung, M., Vogel, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intramolecular+chromium(II)-catalyzed+pinacol+cross+coupling+of+2-Mmethylene-&#945;,&#969;-dicarbonyls.">Intramolecular chromium(II)-catalyzed pinacol cross coupling of 2-Mmethylene-&#945;,&#969;-dicarbonyls.</a> Syn. Lett. , 1054-1058 (2004).</li><li>Appendino, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+of+Modified+Ingenol+Esters.">Synthesis of Modified Ingenol Esters.</a> Eur. J. Org. Chem. , 3413-3420 (1999).</li><li>Spaccini, R., Pastori, N., Clerici, A., Punta, C., Porta, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Key+role+of+Ti(IV)+in+the+selective+radical-radical+cross-coupling+mediated+by+the+Ingold-Fischer+effect.">Key role of Ti(IV) in the selective radical-radical cross-coupling mediated by the Ingold-Fischer effect.</a> J. Am. Chem. Soc. 130, 18018-18024 (2008).</li><li>Leonard, J., Lyfo, B., Procter, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Advanced Practical Organic Chemistry. , (2013).</li><li>Scheffler, U., Stoesser, R., Mahrwald, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retropinacol+/+cross-pinacol+coupling+reactions+-+a+catalytic+access+to+1,2-unsymmetrical+diols.">Retropinacol / cross-pinacol coupling reactions - a catalytic access to 1,2-unsymmetrical diols.</a> Adv. Synth. Cat. 354, 2648-2652 (2012).</li></ol>

Gli autori dichiarano interessi finanziari concorrenti.

Una diminuzione generale dei tempi di reazione e rendimenti più elevati rispetto, da parte dispiegamento di composti carbonilici ricca di elettroni (confrontare ingresso 3 con 17, la tabella 1 o ingresso 19 con 13, Tabella 2). Inoltre, nelle reazioni di chetoni con sostituenti ingombranti riduzione delle rese si osserva in condizioni analoghe (confrontare entrata 12 con 11, Tabella 2). Sebbene una vasta gamma di ...

La reazione di accoppiamento pinacolica è un metodo generale e comunemente usato per la preparazione di dioli vicinali simmetricamente (1,2-dioli, pinacols). Per le recensioni complete in questo campo, vedi riferimenti Hirao 1, Chatterjee e Joshi 2, Ladipo 3, e Gansäuer e Bluhm 4. In contrasto a ciò, solo pochi rapporti sono stati pubblicati di sottoporre una realizzazione efficiente delle reazioni di accoppiamento incrociato Pinacol per dare il corrispondente asimmetrici 1,2-dioli (titanio (IV) cloruro / manganese 5, samario (II) ioduro 6, magnesio / trimetilclorosilano 7, vanadio (II) 8, zirconio / stagno 9, e itterbio 10). Pertanto, la reazione di accoppiamento incrociato pinacolica intermolecolare rimane ancora una sfida in chimica organica, in particolare l&#39;esecuzione catalitico di questa trasformazione. La formazione di prodotti accoppiamento incrociato è cineticamente disfavoredin condizioni di accoppiamento pinacolo classica. Per ottenere una quantità sufficiente di prodotto asimmetrico ritardato aggiunta di un composto carbonilico è possibile. Esistono alcuni esempi che stanno sviluppando questo concetto, ma si basano su diverse manipolazioni sperimentali specifici e, quindi, non può essere generalizzata. Inoltre, l&#39;eccesso necessaria di un composto carbonilico in queste trasformazioni comportato una separazione laboriosa di una miscela complessa di prodotti 11. Una alternativa a questo scopo è rappresentato dalla precomplexation di un reagente di rendering quantità equimolare di un reagente aggiuntivo necessario. Vari esempi di una reazione reversibile pinacolo sono stati descritti 12. Questi conducono alla considerazione che tali condizioni possono essere un punto di partenza per la sintesi selettiva di prodotti accoppiamento incrociato. Da un metallo a basso valente nonché una specie reattiva radicale è formato simultaneamente in situ, Dioli asimmetriche potrebbero essere formate esclusivamente in presenza di un adatto reagente carbonile. Per quanto a nostra conoscenza tale metodo non è stato riportato in precedenza (Porta et al. Descritto una fenditura pinacolo comparabile e accoppiamento successiva dalla realizzazione aggiuntiva di quantità stechiometriche di AIBN (2,2 &#39;-azo-bis-isobutirronitrile) per generare i radicali richiesti) 13. Qui un protocollo viene visualizzato che fornisce un rapido e semplice accesso a operativamente asimmetrici 1,2-dioli. I prodotti Pinacol asimmetriche sono per lo più accessibili in ottime rese (&gt; 95%). Indesiderati prodotti simmetricamente Pinacol non vengono rispettate. Questa nuova metodologia trasversale pinacolica si basa su una sequenza di accoppiamento retropinacol / cross-pinacolo. Sarà dimostrato nella seguente da reazioni rappresentativi di benzopinacole (1,1,2,2-tetrafenil-1 ,2-etandiolo, 1) con 2-ethylbutyraldehyde (nella serie aldeide) e with dietilchetone (nella serie chetone).

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:363px;">1.2-Dichloromethane</td>
			<td style="width:179px;">Sigma-Aldrich</td>
			<td style="width:137px;">319929</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Titanium(IV)tert-butoxide</td>
			<td>VWR International</td>
			<td>200014-852</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">2-Ethylbutyraldehyde</td>
			<td>Sigma-Aldrich</td>
			<td>110094</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Benzopinacol</td>
			<td>Aldrich</td>
			<td>B9807</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Triethylchlorosilane</td>
			<td>Aldrich</td>
			<td>&#160;235067</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">hexane, certified ACS</td>
			<td>Fisher scientific</td>
			<td>H29220</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">acetone, certified ACS</td>
			<td>ACROS</td>
			<td>42324</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ammonium chloride</td>
			<td>ACROS</td>
			<td>19997</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium hydrogen carbonate</td>
			<td>ACROS</td>
			<td>12336</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Magnesium sulphate</td>
			<td>ACROS</td>
			<td>41348</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="26">
			<td height="26" style="height:26px;">silica gel 60 F254 TLC plates</td>
			<td>VWR International</td>
			<td>1,057,140,001</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">&#160;silica gel, 0.035-0.070 for flash-chromatography</td>
			<td>ACROS</td>
			<td>240360300</td>
			<td style="width:79px;"></td>
		</tr>
	</tbody>
</table>

retropinacol/cross-pinacol coupling reactions - a catalytic access to 1,2-unsymmetrical diols

Asimmetrici 1,2-dioli sono difficilmente raggiungibili con i processi di accoppiamento pinacolo riduttive. Una corretta esecuzione di tale trasformazione è associato a un riconoscimento chiaro e rigoroso differenziazione dei due composti carbonilici simili (aldeidi → secondarie 1,2-dioli o chetoni → terziario 1,2-dioli). Questo fine-tuning è ancora una sfida e un problema irrisolto per un chimico organico. Esistono diversi rapporti sulla corretta esecuzione di questa trasformazione, ma non possono essere generalizzati. Qui si descrive un processo catalitico diretto pinacol accoppiamento che procede attraverso una sequenza di accoppiamento retropinacol / cross-pinacolo. Così, asimmetrici sostituiti 1,2-dioli possono essere raggiunti con rese quasi quantitative mediante una performance operativamente semplice in condizioni molto blande. Tecniche artificiali, come le tecniche siringa pompa o aggiunte ritardato di reagenti non sono necessarie. La procedura descriviamo fornisce un rapido accesso allaprodotti cross-Pinacol (1,2-dioli, dioli vicinali). Un&#39;ulteriore estensione di questo nuovo processo, ad esempio una performance enantioselettiva potrebbe fornire uno strumento molto utile per la sintesi di asimmetrici chirali 1,2-dioli.

Nelle reazioni di tetrafenil-1 ,2-etandiolo 1 e acetone in presenza di quantità catalitiche di titanio (IV)-alcossidi abbiamo osservato la formazione di 1,1-difenil-1 ,2-diolo 4a e allo stesso tempo la formazione di benzofenone 3 (Schema 1). La corrispondente simmetrica 1,2-diolo formata da un accoppiamento pinacolo competitivo di acetone non è stato rilevato. Tuttavia, per ottenere conversioni quantitative tempi di reazione estremamente lunghi e inaccettabili erano t...

Watch this Scientific Journal Video about Retropinacol/Cross-pinacol Coupling Reactions - A Catalytic Access to 1,2-Unsymmetrical Diols at JoVE.com

Retropinacol/Cross-pinacol Coupling Reactions - A Catalytic Access to 1,2-Unsymmetrical Diols

Un conto innovativo per la sintesi di 1,2-dioli asimmetrici basati su un meccanismo di accoppiamento retropinacol / cross-pinacolica è descritto. A causa dell&#39;esecuzione catalitica di questa reazione un notevole miglioramento rispetto ai tradizionali raccordi trasversale Pinacol è raggiunto.

Retropinacol / Cross-Pinacol Coupling Reazioni - Una catalitico Accesso al 1,2-asimmetriche Dioli

Unsymmetrical 1,2-diols are hardly accessible by reductive pinacol coupling processes. A successful execution of such a transformation is bound to a clear ...

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12.9K Views.  Humboldt University of Berlin.  Un conto innovativo per la sintesi di 1,2-dioli asimmetrici basati su un meccanismo di accoppiamento retropinacol / cross-pinacolica è descritto. A causa dell'esecuzione catalitica di questa reazione un notevole miglioramento rispetto ai tradizionali raccordi trasversale Pinacol è raggiunto. 

Video: Retropinacol/Cross-pinacol Coupling Reactions - A Catalytic Access to 1,2-Unsymmetrical Diols

Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium Under Mild Reaction Conditions

Dichloro-bis(aminophosphine) complexes of palladium with the general formula of [(P{(NC5H10)3-n(C6H11)n})2Pd(Cl)2] (where n = 0-2), belong to a new family of easy accessible, very cheap, and air stable, but highly active and universally applicable C-C cross-coupling catalysts with an excellent functional group tolerance. Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium [(P(NC5H10)3)2Pd(Cl)2] (1), the least stable complex within this series towards protons; e.g. in the form of water, allows an eased nanoparticle formation and hence, proved to be the most active Heck catalyst within this series at 100 &#176;C and is a very rare example of an effective and versatile catalyst system that efficiently operates under mild reaction conditions. Rapid and complete catalyst degradation under work-up conditions into phosphonates, piperidinium salts and other, palladium-containing decomposition products assure an easy separation of the coupling products from catalyst and ligands. The facile, cheap, and rapid synthesis of 1,1',1"-(phosphinetriyl)tripiperidine and 1 respectively, the simple and convenient use as well as its excellent catalytic performance in the Heck reaction at 100 &#176;C make 1 to one of the most attractive and greenest Heck catalysts available.
We provide here the visualized protocols for the ligand and catalyst syntheses as well as the reaction protocol for Heck reactions performed at 10 mmol scale at 100 &#176;C and show that this catalyst is suitable for its use in organic syntheses.

Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1&#039;,1&#039;&#039;-phosphinetriyltripiperidine]}palladium Under Mild Reaction Conditions

Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium [(P(NC5H10)3)2Pd(Cl)2] (1) is an easy accessible, cheap, and air stable, but highly active Heck catalyst with an excellent functional group tolerance that efficiently operates under mild reaction conditions to give the coupling products in very high yields.

Mizoroki-Heck reazioni di cross-coupling catalizzate da dicloro {bis [1,1 &#39;, 1&#39;&#39; - (phosphinetriyl) tripiperidine]} palladio Sotto lievi condizioni di reazione

Dichloro-bis(aminophosphine) complexes of palladium with the general formula of [(P{(NC5H10)3-n(C6H11)n})2Pd(Cl)2] (where n = 0-2), belong to a new family ...

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Hot Biological Catalysis: Isothermal Titration Calorimetry to Characterize Enzymatic Reactions

Isothermal titration calorimetry (ITC) is a well-described technique that measures the heat released or absorbed during a chemical reaction, using it as an intrinsic probe to characterize virtually every chemical process. Nowadays, this technique is extensively applied to determine thermodynamic parameters of biomolecular binding equilibria. In addition, ITC has been demonstrated to be able of directly measuring kinetics and thermodynamic parameters (kcat, KM, &#916;H) of enzymatic reactions, even though this application is still underexploited. As heat changes spontaneously occur during enzymatic catalysis, ITC does not require any modification or labeling of the system under analysis and can be performed in solution. Moreover, the method needs little amount of material. These properties make ITC an invaluable, powerful and unique tool to study enzyme kinetics in several applications, such as, for example, drug discovery.
In this work an experimental ITC-based method to quantify kinetics and thermodynamics of enzymatic reactions is thoroughly described. This method is applied to determine kcat and KM of the enzymatic hydrolysis of urea by Canavalia ensiformis (jack bean) urease. Calculation of intrinsic molar enthalpy (&#916;Hint) of the reaction is performed. The values thus obtained are consistent with previous data reported in literature, demonstrating the reliability of the methodology.

Isothermal titration calorimetry measures heat flow released or absorbed in chemical reactions. This method can be used to quantify enzyme-catalysis. In this paper, the protocol for instrumental setup, experiment running, and data analysis is generally described, and applied to the characterization of enzymatic urea hydrolysis by jack bean urease.

Hot Catalisi biologica: Calorimetria isotermica di titolazione per caratterizzare reazioni enzimatiche

Isothermal titration calorimetry (ITC) is a well-described technique that measures the heat released or absorbed during a chemical reaction, using it as ...

Amide Coupling Reaction for the Synthesis of Bispyridine-based Ligands and Their Complexation to Platinum as Dinuclear Anticancer Agents

Amide coupling reactions can be used to synthesize bispyridine-based ligands for use as bridging linkers in multinuclear platinum anticancer drugs. Isonicotinic acid, or its derivatives, are coupled to variable length diaminoalkane chains under an inert atmosphere in anhydrous DMF or DMSO with the use of a weak base, triethylamine, and a coupling agent, 1-propylphosphonic anhydride. The products precipitate from solution upon formation or can be precipitated by the addition of water. If desired, the ligands can be further purified by recrystallization from hot water. Dinuclear platinum complex synthesis using the bispyridine ligands is done in hot water using transplatin. The most informative of the chemical characterization techniques to determine the structure and gross purity of both the bispyridine ligands and the final platinum complexes is 1H NMR with particular analysis of the aromatic region of the spectra (7-9 ppm). The platinum complexes have potential application as anticancer agents and the synthesis method can be modified to produce trinuclear and other multinuclear complexes with different hydrogen bonding functionality in the bridging ligand.

This protocol describes the use of amide coupling reactions of isonicotinic acid and diaminoalkanes to form bridging ligands suitable for use in the synthesis of multinuclear platinum complexes, which combine aspects of the anticancer drugs BBR3464 and picoplatin.

Ammide Accoppiamento di reazione per la sintesi di leganti a base di Bispyridine e il loro Complessazione di platino come diciclici agenti antitumorali

Amide coupling reactions can be used to synthesize bispyridine-based ligands for use as bridging linkers in multinuclear platinum anticancer drugs. ...

Real-time Monitoring of Reactions Performed Using Continuous-flow Processing: The Preparation of 3-Acetylcoumarin as an Example

By using inline monitoring, it is possible to optimize reactions performed using continuous-flow processing in a simple and rapid way. It is also possible to ensure consistent product quality over time using this technique. We here show how to interface a commercially available flow unit with a Raman spectrometer. The Raman flow cell is placed after the back-pressure regulator, meaning that it can be operated at atmospheric pressure. In addition, the fact that the product stream passes through a length of tubing before entering the flow cell means that the material is at RT. It is important that the spectra are acquired under isothermal conditions since Raman signal intensity is temperature dependent. Having assembled the apparatus, we then show how to monitor a chemical reaction, the piperidine-catalyzed synthesis of 3-acetylcoumarin from salicylaldehyde and ethyl acetoacetate being used as an example. The reaction can be performed over a range of flow rates and temperatures, the in-situ monitoring tool being used to optimize conditions simply and easily.

Real-time monitoring allows for fast optimization of reactions performed using continuous-flow processing. Here the preparation of 3-acetylcoumarin is used as an example. The apparatus for performing in-situ Raman monitoring is described, as are the steps required to optimize the reaction.

Monitoraggio in tempo reale delle reazioni eseguita utilizzando la lavorazione a flusso continuo: La preparazione di 3-Acetylcoumarin come un esempio

By using inline monitoring, it is possible to optimize reactions performed using continuous-flow processing in a simple and rapid way. It is also possible ...

Highly Stereoselective Synthesis of 1,6-Ketoesters Mediated by Ionic Liquids: A Three-component Reaction Enabling Rapid Access to a New Class of Low Molecular Weight Gelators

In organic chemistry ionic liquids (ILs) have emerged as safe and recyclable reaction solvents. In the presence of a base ILs can be deprotonated to form catalytically active N-Heterocyclic Carbenes (NHCs). Here we have used ILs as precatalysts in the addition of &#945;,&#946;-unsaturated aldehydes to chalcones to form 1,6-ketoesters, incorporating an anti-diphenyl moiety in a highly stereoselective fashion. The reaction has a broad substrate scope and several functional groups and heteroaromatics can be integrated into the ketoester backbone in generally good yields with maintained stereoselectivity. The reaction protocol is robust and scalable. The starting materials are inexpensive and the products can be obtained after simple filtration, avoiding solvent-demanding chromatography. Furthermore, the IL can be recycled up to 5 times without any loss of reactivity. Moreover, the 1,6-ketoester end product is a potent gelator in several hydrocarbon based solvents. The method enables rapid access to and evaluation of a new class of low molecular weight gelators (LMWGs) from recyclable and inexpensive starting materials.

Ionic liquids (ILs) mediate fast, simple and cheap access to 1,6-ketoesters in high diastereoselectivities and good yields. The reaction protocol is robust and the 1,6-ketoesters can be obtained in gram scale after a simple filtration protocol. Moreover, the 1,6-ketoesters are potent gelators in hydrocarbon solvents.

Sintesi altamente stereoselettiva di 1,6-chetoesteri Mediata da liquidi ionici: una reazione a tre componenti Abilitazione accesso rapido a una nuova classe di basso peso molecolare Gelators

In organic chemistry ionic liquids (ILs) have emerged as safe and recyclable reaction solvents. In the presence of a base ILs can be deprotonated to form ...

A Simple, Low-cost, and Robust System to Measure the Volume of Hydrogen Evolved by Chemical Reactions with Aqueous Solutions

There is a growing research interest in the development of portable systems which can deliver hydrogen on-demand to proton exchange membrane (PEM) hydrogen fuel cells. Researchers seeking to develop such systems require a method of measuring the generated hydrogen. Herein, we describe a simple, low-cost, and robust method to measure the hydrogen generated from the reaction of solids with aqueous solutions. The reactions are conducted in a conventional one-necked round-bottomed flask placed in a temperature controlled water bath. The hydrogen generated from the reaction in the flask is channeled through tubing into a water-filled inverted measuring cylinder. The water displaced from the measuring cylinder by the incoming gas is diverted into a beaker on a balance. The balance is connected to a computer, and the change in the mass reading of the balance over time is recorded using data collection and spreadsheet software programs. The data can then be approximately corrected for water vapor using the method described herein, and parameters such as the total hydrogen yield, the hydrogen generation rate, and the induction period can also be deduced. The size of the measuring cylinder and the resolution of the balance can be changed to adapt the setup to different hydrogen volumes and flow rates.

The study of methods to generate on-demand hydrogen for fuel cells continues to grow in importance. However, systems to measure hydrogen evolution from the reaction of chemicals with water can be complicated and expensive. This article details a simple, low-cost, and robust method to measure the evolution of hydrogen gas.

Un semplice, a basso costo, e robusto sistema per misurare il volume di idrogeno Evolved da reazioni chimiche con soluzioni acquose

There is a growing research interest in the development of portable systems which can deliver hydrogen on-demand to proton exchange membrane (PEM) ...

Laboratory Production of Biofuels and Biochemicals from a Rapeseed Oil through Catalytic Cracking Conversion

The work is based on a reported study which investigates the processability of canola oil (bio-feed) in the presence of bitumen-derived heavy gas oil (HGO) for production of transportation fuels through a fluid catalytic cracking (FCC) route. Cracking experiments are performed with a fully automated reaction unit at a fixed weight hourly space velocity (WHSV) of 8 hr-1, 490-530 &#176;C, and catalyst/oil ratios of 4-12 g/g. When a feed is in contact with catalyst in the fluid-bed reactor, cracking takes place generating gaseous, liquid, and solid products. The vapor produced is condensed and collected in a liquid receiver at -15 &#176;C. The non-condensable effluent is first directed to a vessel and is sent, after homogenization, to an on-line gas chromatograph (GC) for refinery gas analysis. The coke deposited on the catalyst is determined in situ by burning the spent catalyst in air at high temperatures. Levels of CO2 are measured quantitatively via an infrared (IR) cell, and are converted to coke yield. Liquid samples in the receivers are analyzed by GC for simulated distillation to determine the amounts in different boiling ranges, i.e., IBP-221 &#176;C (gasoline), 221-343 &#176;C (light cycle oil), and 343 &#176;C+ (heavy cycle oil). Cracking of a feed containing canola oil generates water, which appears at the bottom of a liquid receiver and on its inner wall. Recovery of water on the wall is achieved through washing with methanol followed by Karl Fischer titration for water content. Basic results reported include conversion (the portion of the feed converted to gas and liquid product with a boiling point below 221 &#176;C, coke, and water, if present) and yields of dry gas (H2-C2's, CO, and CO2), liquefied petroleum gas (C3-C4), gasoline, light cycle oil, heavy cycle oil, coke, and water, if present.

This paper presents an experimental method to produce biofuels and biochemicals from canola oil mixed with a fossil-based feed in the presence of a catalyst at mild temperatures. Gaseous, liquid, and solid products from a reaction unit are quantified and characterized. Conversion and individual product yields are calculated and reported.

Laboratorio produzione di biocarburanti e biochimici da un olio di colza attraverso cracking catalitico di conversione

The work is based on a reported study which investigates the processability of canola oil (bio-feed) in the presence of bitumen-derived heavy gas oil ...

A Simple and Efficient Protocol for the Catalytic Insertion Polymerization of Functional Norbornenes

Norbornene can be polymerized by a variety of mechanisms, including insertion polymerization whereby the double bond is polymerized and the bicyclic nature of the monomer is conserved. The resulting polymer, polynorbornene, has a very high glass transition temperature, Tg, and interesting optical and electrical properties. However, the polymerization of functional norbornenes by this mechanism is complicated by the fact that the endo substituted norbornene monomer has, in general, a very low reactivity. Furthermore, the separation of the endo substituted monomer from the exo monomer is a tedious task. Here, we present a simple protocol for the polymerization of substituted norbornenes (endo:exo ca. 80:20) bearing either a carboxylic acid or a pendant double bond. The process does not require that both isomers be separated, and proceeds with low catalyst loadings (0.01 to 0.02 mol%). The polymer bearing pendant double bonds can be further transformed in high yield, to afford a polymer bearing pendant epoxy groups. These simple procedures can be applied to prepare polynorbornenes with a variety of functional groups, such as esters, alcohols, imides, double bonds, carboxylic acids, bromo-alkyls, aldehydes and anhydrides.

We describe the catalytic insertion polymerization of 5-norbornene-2-carboxylic acid and 5-vinyl-2-norbornene to form functional polymers with a very high glass transition temperature.

Un protocollo semplice ed efficiente per l&#39;inserimento catalitica polimerizzazione di norborneni funzionali

Norbornene can be polymerized by a variety of mechanisms, including insertion polymerization whereby the double bond is polymerized and the bicyclic ...

A Protocol for Safe Lithiation Reactions Using Organolithium Reagents

Organolithium reagents are powerful tools in the synthetic chemist&#39;s toolbox. However, the extreme pyrophoric nature of the most reactive reagents warrants proper technique, thorough training, and proper personal protective equipment. To aid in the training of researchers using organolithium reagents, a thorough, step-by-step protocol for the safe and effective use of tert-butyllithium on an inert gas line or within a glovebox is described. As a model reaction, preparation of lithium tert-butyl amide by the reaction of tert-butyl amine with one equivalent of tert-butyl lithium is presented.

The safe and proper use of organolithium reagents is described.

Un protocollo per reazioni sicuro litiazione Utilizzando organolitio Reagenti

Organolithium reagents are powerful tools in the synthetic chemist&#39;s toolbox. However, the extreme pyrophoric nature of the most reactive reagents ...

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from benzimidazolium salts. Detailed and generalized protocols are also presented for testing the catalytic activity of such complexes in arylation and Suzuki-Miyaura cross-coupling reactions. Representative results are shown for the catalytic activity of the four complexes in arylation and Suzuki-Miyaura type reactions. For each of the reactions investigated, at least one of the four complexes successfully catalyzed the reaction, qualifying them as promising candidates for catalysis of many carbon-carbon bond-forming reactions. The protocols presented are general enough to be adapted for the synthesis, purification and catalytic activity testing of new palladium N-heterocyclic carbene complexes.

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from benzimidazolium salts. The complexes were tested for catalytic activity in arylation and Suzuki-Miyaura reactions. For each reaction investigated, at least one of the four complexes successfully catalyzed the reaction.

Palladio<em&gt; N</em&gt; Complessi di Carbene eterocicliche: Sintesi dei sali di benzimidazolium e attività catalitica in reazioni di formazione di legame di carbonio-carbonio

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from ...