Nitrile anion cyclization with epoxysilanes followed by Brook rearrangement/ring-opening of cyclopropane nitriles/alkylation
Nitrile anion cyclization with epoxysilanes followed by Brook rearrangement/ring-opening of cyclopropane nitriles/alkylation
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DOI：
10.1021/jo0519413
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发表时间：
2005-12-09
影响因子：
3.6
通讯作者：
Takeda, K
中科院分区：
文献类型：
--
作者：
Okugawa, S;Masu, H;Takeda, K
[图形]δ -硅基- γ、δ -环氧戊腈衍生物9-12与碱和烷基化剂反应生成(Z)- δ -硅氧基- γ、δ -不饱和戊腈衍生物，反应过程包括通过环氧腈环化形成环丙烷衍生物，然后是布鲁克重排和阴离子诱导的环丙烷环裂解。反式环氧化物的(Z)衍生物的形成可以用反应途径来解释，该反应途径包括-腈碳离子对环氧化物的反向位移和O-Si键的形成，随后是包括布鲁克重排和环丙烷从旋转体中消除环裂变的反模式19。(E)-异构体完全是从顺式环氧化物和-环丙基- -硅基甲醇衍生物26中获得的，这一事实为所提出的途径提供了实验支持。
[GRAPHICS]The reaction of delta-silyl-gamma,delta-epoxypentanenitrile derivatives 9-12 with a base and an alkylating agent affords (Z)-delta-siloxy-gamma,delta-unsaturated pentanenitrile derivatives via a tandem process that involves the formation of a cyclopropane derivative by epoxy nitrile cyclization followed by Brook rearrangement and an anion-induced cleavage of the cyclopropane ring. Exclusive formation of a (Z)-derivative from trans-epoxides is explained by the reaction pathway that involves a backside displacement of the epoxide by the alpha-nitrile carbanion and the O-Si bond formation followed by concerted processes involving Brook rearrangement and the anti-mode of eliminative ring fission of the cyclopropane from the rotamer 19. The fact that (E)-isomers are exclusively obtained from cis-epoxides and alpha-cyclopropyl-alpha-silylcarbinol derivative 26 provides experimental support for the proposed pathway.