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Minimization of Amounts of Catalyst and Solvent in NHC-Catalyzed Benzoin Reactions of Solid Aldehydes: Mechanistic Consideration of Solid-to-Solid Conversion and Total Synthesis of Isodarparvinol B.
ACS Omega ( IF 3.7 ) Pub Date : 2020-04-20 , DOI: 10.1021/acsomega.0c01141 Kenta Iwai 1 , Masakazu Ono 1 , Yoshiko Nanjo 1 , Tadashi Ema 1
ACS Omega ( IF 3.7 ) Pub Date : 2020-04-20 , DOI: 10.1021/acsomega.0c01141 Kenta Iwai 1 , Masakazu Ono 1 , Yoshiko Nanjo 1 , Tadashi Ema 1
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Attempts were made to minimize the amounts of catalyst and solvent in the NHC-catalyzed benzoin reactions of solid aldehydes. In some case, solid-to-solid conversions proceeded in the solvent-free NHC-catalyzed benzoin reactions. Even if a mixture of the substrate, N-heterocyclic carbene (NHC) precursor, and inorganic base was initially a powdery solid, the reaction did proceed at reaction temperature lower than the melting points of each compound. The solid mixture partially melted or became a slurry or suspension in the meantime. We call this solid/liquid mixture a semisolid state. The reaction giving an optically active product was faster than that giving a racemic mixture of the same product. Melting-point depression was observed for a series of mixtures of the substrate and product in different substrate/product ratios. Solvent-free solid-to-solid conversions were accelerated by the formation of a semisolid state resulting from the melting-point depression of the solid substrate accompanied by the product formation. In the case of solid substrates with high melting points, melting-point depression was useless, and the addition of a small amount of solvent was needed. The first total synthesis of isodarparvinol B was achieved via the NHC-catalyzed intramolecular benzoin reaction using a small amount of solvent as an additive.
中文翻译：
在NHC催化的固体醛的苯偶姻反应中催化剂和溶剂的量最少：固-固转换和异波达木醇B的全合成的机理考虑。
尝试使NHC催化的固体醛的安息香反应中的催化剂和溶剂的量最小化。在某些情况下，固体到固体的转化是在无溶剂的NHC催化的安息香反应中进行的。即使底物，N-杂环卡宾（NHC）前体和无机碱的混合物最初是粉末状固体，反应的确在低于每种化合物熔点的反应温度下进行。同时，固体混合物部分熔融或变成淤浆或悬浮液。我们称这种固/液混合物为半固态。得到旋光活性产物的反应比得到相同产物的外消旋混合物的反应快。在底物/产品比例不同的情况下，观察到一系列底物和产品混合物的熔点降低。通过固体基质的熔点降低伴随着产物形成而形成的半固态促进了无溶剂的固体到固体的转化。在具有高熔点的固体基质的情况下，熔点降低是无用的，并且需要添加少量的溶剂。通过使用少量溶剂作为添加剂的NHC催化的分子内安息香反应，可实现异darparvinol B的第一个全合成。
更新日期：2020-04-20
中文翻译：
在NHC催化的固体醛的苯偶姻反应中催化剂和溶剂的量最少：固-固转换和异波达木醇B的全合成的机理考虑。
尝试使NHC催化的固体醛的安息香反应中的催化剂和溶剂的量最小化。在某些情况下，固体到固体的转化是在无溶剂的NHC催化的安息香反应中进行的。即使底物，N-杂环卡宾（NHC）前体和无机碱的混合物最初是粉末状固体，反应的确在低于每种化合物熔点的反应温度下进行。同时，固体混合物部分熔融或变成淤浆或悬浮液。我们称这种固/液混合物为半固态。得到旋光活性产物的反应比得到相同产物的外消旋混合物的反应快。在底物/产品比例不同的情况下，观察到一系列底物和产品混合物的熔点降低。通过固体基质的熔点降低伴随着产物形成而形成的半固态促进了无溶剂的固体到固体的转化。在具有高熔点的固体基质的情况下，熔点降低是无用的，并且需要添加少量的溶剂。通过使用少量溶剂作为添加剂的NHC催化的分子内安息香反应，可实现异darparvinol B的第一个全合成。
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