Este trabalho foi financiado pela Fundação Nacional de ciências naturais da China (21471037), fundos de ciência Natural de Guangdong de ilustres jovens estudiosos (15ZK0307), ciência e tecnologia de planejamento de projeto da província de Guangdong (2017A050506051) e o Conselho de bolsas de investigação de Hong Kong [GRF 11303414].

Atenção: Por favor consulte todas as fichas de dados de segurança relevantes antes do uso. Thiomethoxide de metilo dissulfeto e de sódio são fortemente malcheirosa e deve ser tratada em uma coifa. Sódio metálico é altamente reativo e requer precauções especiais de segurança contra incêndio potencial e riscos de explosão. Além do uso de uma coifa, equipamento de proteção individual (óculos de segurança, luvas, jaleco, calça comprida e sapatos fechados) deve ser empregado corretamente. Porções dos seguintes procedimentos envolvem padrão, técnicas de manipulação ar-livre.
1. preparação de Thiomethoxide de sódio (CH3SNa)
<ol><li>Conecte o balão de 200 mL de Schlenk para um distribuidor de vácuo do gás. Evacuar o balão e então aterramento com N2 três vezes, tal que o balão é preenchido com uma pressão de2 N ligeiramente positiva. Nota: Um método similar de preparar CH3SNa foi mencionado brevemente na literatura, mas sem procedimentos detalhados foram fornecidos27,28.</li>
	<li>Tire um bloco de sódio metálico do reservatório de óleo de querosene. Usar uma toalha de papel para limpar o óleo residual na superfície e usar uma faca para raspar a camada de óxido na superfície. Rapidamente cortar 6,7 g do sódio metálico (0,29 mol) em pedaços pequenos (ex., tamanho de soja) e transferir imediatamente os pequenos pedaços no balão de 200 mL Schlenk sob um fluxo de contador de N2. Sele o balão com um septo imediatamente. Nota: Para reduzir a exposição ao ar, um pode cortar o sódio com alguma variação da quantidade de 6,7 g e ajustar as quantidades de THF e dimetil dissulfeto de acordo com a quantidade real de sódio usado.</li>
	<li>Transferi 80 mL de um THF anidro, sem ar dentro da balão através de cânula sob a proteção de N2 da linha de Schlenk. Retirar 14,0 mL de dissulfeto dimetil (0,158 moles; pre-purgada com N2) em uma seringa e injetar na gota a gota sob a proteção de N2 o balão. Cuidado: Dissulfeto dimetil é malcheiroso e deve ser tratado em uma coifa.</li>
	<li>Substitua o septo com uma rolha de vidro. Agite a mistura de reação em temperatura ambiente por 24 h e depois a 60 ° C por 3 h. Nota: A mistura de reação tornou-se viscoso, agitando à temperatura ambiente; Quando aquecida a 60 ° C, a mistura pode ser agitada mais facilmente e, portanto, acelerar a reação para a sua conclusão.</li>
	<li>Com a temperatura mantida a cerca de 60 ° C, use um fluxo de N2 (0,2 L/min) para explodir fora a maioria dos solvente THF e o dissulfeto dimetil excesso, até que apareça um sólido seco. Usar uma armadilha fria (EG., gelo seco-acetona) para coletar o THF e dimetil dissulfeto na vazão.</li>
	<li>Evacuar o restante mistura sólida com um óleo bombear para cerca de 2 h remover o residual THF e dimetil dissulfeto e em seguida aterre com N2 para obter um sólido amarelo-luz (19,8 g, 97%). Armazene o produto sólido CH3SNa em uma atmosfera de nitrogênio no escuro. Nota: Para proteger a bomba de óleo do vácuo, uma armadilha fria deve ser usada durante o bombeamento.</li>
</ol>2. preparação de trifenileno 2,3,6,7,10,11-hexaquis (pentanoylthio) (HVaTT) como um vinculador tiol protegido
<ol><li>Carregar 0,664 g de CH3SNa (9,0 mmol) em um frasco de 50 mL Schlenk sob um fluxo de contador de N2 (i. e., conectado como acima para um distribuidor de vácuo do gás sob a proteção de N2 ). Nota: CH3SNa é sensível ao ar e absorve facilmente a água. Para minimizar a exposição ao ar, um pode rapidamente pesar uma quantidade específica e adicioná-lo ao balão e então ajustar a quantidade do outro reagente, 2,3,6,7,10,11-hexabromotriphenylene (HBT) e, por conseguinte. Cuidado: Sólido CH3SNa tem um cheiro forte e deve ser tratada em uma coifa.</li>
	<li>Adicionar g 0,216 de HBT (0.30 mmol) ao balão sob um fluxo de contador de N2e foca o balão com um septo.</li>
	<li>Transferi 10 mL de anidro e mal ventilado 1,3-dimetil-2-imidazolidinon (DMEU) para o balão via cânula sob a proteção de N2 da linha de Schlenk.</li>
	<li>Substituir o septo com uma rolha de vidro normal e agitar a mistura de reação e usar um banho de sal para aquecê-lo a 240 ° C por 48 h sob N2.</li>
	<li>TLC, acompanhamento dos progressos da reação: sob N2, use um conta-gotas de vidro para retirar uma pequena alíquota da mistura de reação (cerca de 0,1 mL) e imediatamente injetá-lo em uma amostra de líquido pura de cloreto de valeroyl (cerca de 0,1 mL) em um plástico microcentrifuga frasco e em seguida agitar durante 1 min; a mistura deve imediatamente transformar turva com uma cor cinzento-branco. Adicionar 0,4 mL de água desionizada e 0,1 mL de acetato de etila, fechar a tampa e sacuda por alguns segundos. Nota: Se a reação completou-se já, não haverá nada que aparece entre as camadas de água e acetato de etila. Se não, uma substância insolúvel branca aparecerá entre as duas camadas.</li>
	<li>Pipeta para fora a parte superior e usá-lo para detectar as placas do TLC. Use o éter de petróleo/acetato de etila 4:1 para desenvolver a placa de TLC. Para uma reação completa, a molécula alvo aparece como um regular ponto em torno de Rf = 0,4 sob uma lâmpada UV.</li>
	<li>Desligar o aquecimento e leve o frasco de reação fora o banho de sal para resfriá-lo à temperatura ambiente e em seguida, usar um banho de gelo para esfriar o frasco até 0 ° C.</li>
	<li>Injete 1,5 mL de cloreto de valeroyl (12,6 mmol) no balão de gota a gota (durante um período de cerca de 2 min) com uma seringa sob N2. Continue mexendo a 0 ° C, durante 2 h. Nota: Adicionar cloreto de valeroyl lentamente e a baixa temperatura ajuda a reduzir a geração de subprodutos.</li>
	<li>Despeje a mistura em 50 mL de água gelada e extrato usando acetato de etila (3 30 mL). Então lave a camada orgânica combinada com água (6 60 mL), seca por anidro MgSO4e remover os compostos voláteis por um evaporador rotativo.</li>
	<li>Isolar o produto bruto oleoso por cromatografia em coluna utilizando 01:10 éter de petróleo/acetato de etila como eluente, que oferece um produto oleoso amarelo-luz após giratória evaporação dos solventes. Usar o éter de petróleo/acetato de etila 4:1 para desenvolver a placa de TLC, Rf = 0,4. Purifica ainda mais o produto oleoso usando a etapa de trituração abaixo.</li>
	<li>Adicionar 5 mL de methanolto o produto oleoso e proceda à sonicação por 2 min. recolher o sólido esbranquiçado resultante usando filtragem aspiração (rendimento: 59%).</li>
</ol>3. preparação de cristais do Material quadro HTT-Pb
<ol><li>Misture 11,4 mg de PbOAc·3H2O (0,030 mmol) em 1,0 mL de etileno diamina em um frasco para fazer uma solução clara.</li>
	<li>Carregar 9,1 mg de HVaTT (0.010 mmol), 2,0 mL de metanol previamente desgaseificado solução de NaOH (70 mmol/L) e 1,0 mL de etileno diamina dentro de um frasco de 10mL vazia e proceda à sonicação por 5 min.</li>
	<li>Adicione a solução de PbOAc à mistura de HVaTT de lisados. Depois da bolha mistura reacional com N2 por 1 min e coloque a tampa de enroscar para selar o frasco.</li>
	<li>Aqueça o frasco a 90 ° C em um forno para 48 h, seguido de refrigerar natural à temperatura ambiente, durante a qual amarelo-laranja, cristais octaédricos apropriados para estudos de difração de raios x do único-cristal foram formados (rendimento: 45%).</li>
	<li>Filtração, fora os cristais de sucção e lavar rapidamente com MeOH. Transferi os cristais com um conta-gotas de vidro em um frasco contendo airless MeOH (5 mL) para armazenamento em temperatura ambiente.</li>
</ol>4. interação de Paraquat Diiodide com cristais HTT-Pb
<ol><li>Usar um pipeta Pasteur de vidro para retirar alguns grãos de cristal único HTT-Pb do estoque MeOH e solte-o sobre um prato de Petri (diâmetro 35 mm e profundidade de 10 mm). Absorver o líquido de metanol por tecido ou papel de filtro (ou deixe o MeOH secar naturalmente) e depois soltar para os cristais de algumas gotas de uma solução aquosa de paraquat diiodide (0,1%, w/w).</li>
	<li>Observar a cor mudança dos cristais a olho nu ou ao microscópio.</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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A reação entre o grupo de bromo e o ânion thiomethoxide aparentemente primeiro produzido o metil Tioéter, que era então desmetilado pelo excesso thiomethoxide para fornecer o produto de ânion thiolate. Para assegurar a conversão completa para o ânion thiolate desejada (especialmente para um substrato polibrominato como HBT), as condições vigorosas de prolongado aquecimento (por exemplo, 240 ° C durante mais de 48 h) com um grande excesso de sódio thiomethoxide (por exemplo, mais de três vez...

Há atualmente grande interesse em empregar forte, polarizada metal-enxofre (EG., metal-thiolate) ligações para a construção de abrir materiais quadro com electrocatalytic reforçada e propriedades condutoras1,2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10. além de promover interação eletrônica e transporte no estado estendido, as ligações de enxofre-metal macias e covalentes também transmitir melhor estabilidade para aplicações em ambientes aquosos. Entre enxofre-equipado blocos de construção, simétricos, multidentate blocos de construção aromáticos policíclicos como 2,3,6,7,10,11-trifenileno hexathiol (HTT)9,11,12,13 , 14 não só fornecer elétrons π altamente polarizados, mas também oferecem vantagens distintas em relação ao projeto de estrutura e síntese. Em primeiro lugar, o núcleo trifenileno rígida e simétrica, em conjunto com os grupos dithiolene quelantes de HTT, serve para bloquear em íons metálicos em motivos de ligação regular, simplificando a previsão estrutural da rede em perspectiva7, 15. juntamente com a geometria rígida e aberta do vinculador enxofre, estruturas de quadro com características de porosidade substancial, muitas vezes podem ser alcançadas no estado sólido.
Um grande desafio na montagem de materiais thiol-equipado metal orangic framework (MOF) está enraizado na síntese de moléculas orgânicas vinculador. Em um protocolo clássico, o grupo tiol tinha que ser derivado do grupo fenol usando o rearranjo de Newman-Kwart do - aril thiocarbamate precursor16,17,18. Esta abordagem, no entanto, envolve passos preparativa elaborados para a molécula precursora de fenol, bem como possíveis complicações de uma transformação de fase sólida de alta temperatura. Outra maneira de fazer tióis utiliza dealkylation redutora de thioethers sob as duras condições de, por exemplo, sódio metálico em amônia líquida19,20,21,22e não é compatível com a carboxila e muitas outras funções de doadores para construção da rede.
Por comparação, o protocolo apresentado aqui tem várias vantagens: segurança, conveniência, custo-eficácia e compatibilidade com outros grupos funcionais (ex., carbonitrilo e pyridinyl). Aquecendo-se vigorosamente o haleto de aromático geralmente barato (EG., hexabromotriphenylene) e o ânion thiomethoxide, o ânion thiolate foi gerado (através do produto intermédio metil Tioéter) e então acylated dar o estábulo e fácil de manusear Tioéster produto-tudo em uma panela.
Descreveremos também um procedimento para a utilização das moléculas Tioéster como forma mascarada de linkers o tiol para aceder a uma rede de dithiolene metal semicondutor e porosa single-cristalino. Ao contrário os altamente reativos tióis autônoma, que tendem a se decompor e complicar a cristalização do metal-thiolate estruturas abertas, o Tioéster pode ser prontamente clivada (EG., por NaOH ou etilenodiamina) em situ para fornecer o espécie de tiol, servindo para atenuar a reação entre as unidades de mercaptan e os centros de metal e consequentemente melhorar a cristalização.
Este protocolo de preparação tiol/Tioéster não foi amplamente utilizado por outros grupos para o emergente campo das estruturas de metal-enxofre, apesar de dealkylations nucleofílicos de alquil aril thioethers por ânions thiolate já foram bem documentados por orgânicos os químicos23,24,25,26. Apresentando este eficiente método sintético para tioésteres e sua utilização para facilitar a cristalização das redes de metal-enxofre, desejamos promover os esforços no sentido de colmatar o fosso intelectual e prático entre a química orgânica sintética e química do estado sólido, a fim de ajudar o desenvolvimento saudável e rápido de estruturas porosas.

<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

Apresentamos um método para a preparação de Tioéster moléculas como o mascarado de linkers o tiol e sua utilização para aceder a uma rede de dithiolene metal semicondutor e poroso no estado cristalino único altamente ordenada. Ao contrário os altamente reativos tióis autônoma, que tendem a se decompor e complicar a cristalização do metal-thiolate estruturas abertas, o Tioéster reage em situ para fornecer as espécies tiol, servindo para mitigar a reação entre o mercaptano unidades e os centros de metal e, consequentemente, melhorar a cristalização. Especificamente, o Tioéster foi sintetizado em um procedimento de um pote: um aromático brometo de (hexabromotriphenylene) reagiu com excesso de sódio thiomethoxide sob condições vigorosas para formar primeiro produto intermédio tioéter. O Tioéter foi então desmetilado pelo excesso thiomethoxide para fornecer o ânion thiolate que foi acylated para formar o produto Tioéster. O Tioéster foi convenientemente purificado por cromatografia de coluna padrão e usado diretamente na síntese de quadro, no qual o NaOH e etilenodiamina servem para reverter em situ do Tioéster para o vinculador tiol para montar o Single-cristalino Pb (II)-rede de dithiolene. Em comparação com outros métodos para a síntese de tiol (EG., por clivagem alquil Tioéter usando sódio amônia líquida e metal), a síntese do Tioéster aqui usa condições simples e econômicos reagentes. Além disso, o produto Tioéster é estável e pode ser convenientemente tratado e armazenado. Mais importante, em contraste com a dificuldade genérica de acesso aberto estruturas cristalinas metal-thiolate, demonstramos que usando o Tioéster in situ formação do vinculador tiol melhora extremamente a cristalinidade do estado sólido produto. Temos a intenção de incentivar os esforços de investigação mais amplos sobre as estruturas de metal-enxofre tecnologicamente importantes através da divulgação do protocolo sintético para o Tioéster, bem como a estrutura cristalina contínua.

O espectro de IR da molécula HVaTT (coletado pelo método de pelota KBr) apresenta a sua mais forte absorção em 1.700 cm-1, em conformidade com o alongamento da carbonila do grupo funcional Tioéster. O espectro de 1H-NMR de HVaTT (400 MHz, CDCl3) revela um singleto em δ 8.47 partir os hidrogênios aromáticos, juntamente com 4 multiplets dos prótons alifáticos: δ 8.47 (s, 6 H, CHAr), 2,75-2.72 (t, J = 7,4, 12 H, CH2), 1,81-1,77 ...

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

Aqui, apresentamos uma síntese de um pote, transição-metal-free de tióis e tioésteres de halogenetos aromáticos e thiomethoxide de sódio, seguido de preparação de monocristais de uma rede de metal-dithiolene usando espécies tiol gerados in situ desde o mais estável e tractable Tioéster.

Síntese de um Bloco de Construção Tiol para a Cristalização de uma Estrutura Semicondutora de Metal-Enxofre com Geometria Giroidal

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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Unit 1

Ethers, Epoxides, Sulfides

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8.9K visualizações.  Guangdong University of Technology. Aqui, apresentamos uma síntese de um pote, transição-metal-free de tióis e tioésteres de halogenetos aromáticos e thiomethoxide de sódio, seguido de preparação de monocristais de uma rede de metal-dithiolene usando espécies tiol gerados in situ desde o mais estável e tractable Tioéster.

Vídeo: 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.

Preparação e Uso de Samário diiodeto (SMI<sub&gt; 2</sub&gt;) Em Organic Synthesis: The Role mecanístico de HMPA e (II) de Ni Sais na Reacção Barbier Samário

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

Química

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.

Síntese e Purificação de Iodoaziridines Envolvendo Quantitative Seleção do Optimal fase estacionária para 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.

Síntese e esfoliação da discotic Zircônio Fosfatos obter cristais coloidais líquidos

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.

Síntese de Programmable principal de cadeia Elastômeros líquido-cristalinos Usando um de dois estágios Reação Tiol-acrilato

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.

Síntese de Cd-livre InP / ZnS Quantum Dots Indicado para aplicações biomédicas

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 como um catalisador heterogéneo para a Síntese de vanilina

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.

Síntese de Bioconjugados de proteínas<em&gt; via</em&gt; Química cisteína-maleimida

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.

Separação sulfato por cristalização selectiva com um ligando 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.

Eletroforética cristalização das membranas ultrafinos estrutura Metal-orgânicos de alto desempenho

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.

Fase sólida síntese de [4,4] Spirocyclic oximas

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 ...

Síntese de um Bloco de Construção Tiol para a Cristalização de uma Estrutura Semicondutora de Metal-Enxofre com Geometria Giroidal

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