EFFECTS OF 16-HETEROSUBSTITUTION ON THE REGIOCHEMISTRY OF THE DEUTERIUM-HOMO REARRANGEMENT
EFFECTS OF 16-HETEROSUBSTITUTION ON THE REGIOCHEMISTRY OF THE DEUTERIUM-HOMO REARRANGEMENT
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DOI：
10.1021/jo00219a031
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发表时间：
1985-01-01
影响因子：
3.6
通讯作者：
WALKER, KAM
中科院分区：
文献类型：
--
作者：
BISCHOFBERGER, N;WALKER, KAM
16. beta。-phenylthio - 16. beta。-苯硒-和16 -。17. alpha -dimethylphenysilyl-substituted 3. beta。通过16 - α的亲核开环制备了-二羟基-5-孕烯-20- 1。17.α。以研究16取代基对D-homo重排的区域化学影响。结果发现，苯基硫基取代基改变了碱催化的酮醇重排过程，导致通常未观察到的17. β .-羟基-17a-酮-17. α的定量生成。-甲基- d -同分异构体，而苯硒基或二甲基苯基硅基取代基则没有影响。因此，只有S，而不是Se或Si，似乎能够有效地稳定α中的负电荷。在过渡状态的位置。然而，在路易斯酸催化下，S、Se和令人惊讶的Si都没有对重排的区域化学产生任何影响，从而产生“正常的”17. α - -羟基-17a-酮-17. β。-methyl-D-homo同分异构体。
The 16.beta.-phenylthio-, 16.beta.-phenylseleno-, and 16.beta.-dimethylphenysilyl-substituted 3.beta.,17.alpha.-dihydroxy-5-pregnen-20-ones have been prepared by nucleophilic ring opening of 16.alpha., 17.alpha.-epoxysteroids in order to study the influence of the 16-substituent on the regiochemistry of the D-homo rearrangement. It was found that the phenylthio substituent redirected the course of the base-catalyzed ketol rearrangement, resulting in quantitative formation of the usually unobserved 17.beta.-hydroxy-17a-keto-17.alpha.-methyl-D-homo isomer, whereas phenylseleno or dimethylphenylsilyl substituents showed no influence. Thus, only S, but not Se or Si, seems capable of effectively stabilizing the negative charge in the .alpha. position in the transition state. On Lewis acid catalysis, however, neither S nor Se nor suprisingly Si had any effect on the regiochemistry of the rearrangements, resulting in the "normal" 17.alpha.-hydroxy-17a-keto-17.beta.-methyl-D-homo isomers.