Catalyzed reactions of acyl anion equivalents
Catalyzed reactions of acyl anion equivalents
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DOI：
10.1002/anie.200301702
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发表时间：
2004-01-01
影响因子：
16.6
通讯作者：
Johnson, JS
中科院分区：
文献类型：
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作者：
Johnson, JS
与涉及烯醇酸盐的催化反应相比，涉及酰基阴离子等价物的类似催化化学的研究受到的关注相当少。[1]这可能部分是由于后一类反应中伴随的挑战。虽然直接催化的Michael或Aldol反应的活化步骤在最简单的分析中可以分解为酸碱化学，但在反应设计中，将醛转化为亲核(D1)中心[2]不是一个简单的问题。有机化学家通常求助于将醛转化为二硫杂环戊烷和受保护的氰醇衍生物等阳离子试剂，这些试剂可以转化为具有较强碱性的衍生碳离子物种。事实证明，这种方法在许多情况下都非常有用，但缺乏它们冷漠的同行的步骤经济和美学吸引力。越来越多的人正致力于通过访问和扩大经典的反应流形来实现羰基-极性逆转：安息香[3]和Stetter[4]反应，从而绕过这些缺点。由氰化物或杂氮卡宾介导的醛与其他醛[式(1)]或α，β-不饱和羰基化合物[式(2)]的反应构成了最直接的酰基阴离子等价方法，并已相应地发展起来。直到最近，人们还不知道酮会进行非酶安息香类行为，尽管Hünig和Wehner早些时候的研究已经表明，在非质子条件下，硅氧基(腈)阴离子可以很容易地加成到酮的亲电体上。[5]丙酮酸供体与酮的脱羧基安息香型加成反应以前被证明是通过各种依赖于二磷酸硫胺素(ThDP)的酶进行的。[6]在没有二氧化碳挤出的情况下，醛/酮偶联的热力学是不确定的，直到Suzuki和他的同事最近的工作表明，更传统的条件(酒精、噻唑类卡宾催化)可以用来影响醛和酮之间的分子内交叉安息香反应[等式(3)；MOM=甲氧基甲基，DBU=1，8-重氮基-
In comparison to catalytic reactions involving enolates, research addressing analogous catalytic chemistry of acyl anion equivalents has received considerably less attention.[1] This may be due in part to the attendant challenges in the latter class of reactions. Whereas the activation steps of a direct catalytic Michael or aldol reaction may, in the simplest analysis, be broken down into acid–base chemistry, the conversion of an aldehyde into a nucleophilic (d1) center [2] is a less straightforward problem in reaction design. Organic chemists typically find recourse in the conversion of aldehydes into umpolung reagents such as dithianes and protected cyanohydrin derivatives, which may be converted into the derived carbanionic species with a strong base. Such approaches have proven extremely useful in a large number of contexts, but lack the step economy and aesthetic appeal of their enolate counterparts. Increasingly, efforts are being directed at circumventing these shortcomings by accessing and augmenting classic reaction manifolds for effecting carbonyl-polarity reversal: the benzoin [3] and Stetter [4] reactions. Reactions of aldehydes with other aldehydes [Eq.(1)] or α, β-unsaturated carbonyl compounds [Eq.(2)] mediated by cyanide or heterazolium carbenes comprise the most direct methods of acyl anion equivalence and have been developed accordingly.Until recently, it was not known that ketones would engage in non-enzymatic benzoin-type behavior, although earlier studies from Hünig and Wehner had shown that silyloxy (nitrile) anions could add readily to ketone electrophiles under aprotic conditions.[5] Decarboxylative benzoin-type additions to ketones with pyruvate donors had previously been documented to proceed with a variety of thiamin diphosphate dependent (ThDP) enzymes.[6] The thermodynamics of an aldehyde/ketone coupling in the absence of CO2 extrusion were uncertain until recent work by Suzuki and co-workers demonstrated that more traditional conditions (alcohol solvent, thiazolium carbene catalysis) could be used to effect intramolecular cross-benzoin reactions between an aldehyde and a ketone [Eq.(3); MOM= methoxymethyl, DBU= 1, 8-diazabicy-