Reflections on spontaneous asymmetric synthesis by amplifying autocatalysis
Reflections on spontaneous asymmetric synthesis by amplifying autocatalysis
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DOI：
10.1039/b307382n
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发表时间：
2003-01-01
影响因子：
3.2
通讯作者：
Brown, JM
中科院分区：
文献类型：
--
作者：
Gridnev, ID;Serafimov, JM;Brown, JM
在通过NMR研究嘧啶-5-醛的ZnR2烷基化的不对称自催化机理的过程中，观察到手性的自发产生。为了发现其起源，进行了系统的研究。即使在干净、新鲜的非玻璃反应容器中，也可以清楚地观察到自发ee，并且不依赖于任何单一反应参数。为了进行比较，证明对映体纯的醇锌催化剂即使以低于微摩尔浓度存在也可以控制反应产物的构型。 Soai 反应系统在没有初始偏差的情况下产生对映体富集产物的高倾向被认为是随机效应的结果。这些在自催化中尤其重要，因为所有最终产物都可以通过少量初始事件的育种而获得。该组中一种对映异构体的统计过量足以在产物中产生可测量的ee。在产物成为活性催化剂之前需要进行二聚，从而有助于该过程。提供了合理化这些观察结果的列举。
Spontaneous generation of chirality was observed in the course of studying the mechanism of asymmetric autocatalysis by NMR in ZnR2 alkylation of pyrimidin-5-aldehydes. A systematic study was carried out in order to discover its origins. Even in clean fresh non-glass reaction vessels spontaneous ee was clearly observed, and was not dependent on any single reaction parameter. For comparison it was demonstrated that enantiomerically pure Zn alkoxide catalyst could control the configuration of the reaction product even when present at below micromolar concentrations. The high propensity of the Soai reaction system to produce an enantiomerically enriched product without initial bias is suggested to result from stochastic effects. These are especially important in autocatalysis because all the final products can be derived by breeding from a small number of initial events. The statistical excess of one enantiomer in that set is sufficient to generate a measurable ee in the product. The process is aided by the requirement for dimerisation before the product is an active catalyst. An enumeration that rationalises these observations is provided.