Tandem radical mediated 5-exo-trig, 6-endo-dig cyclization. Stereoselectivity, alpha-trimethylsilyl effect and the product spread .4.

被引：17

作者：

Breithor, M ^{[1
]}

Herden, U ^{[1
]}

Hoffmann, HMR ^{[1
]}

机构：

[1] UNIV HANNOVER,DEPT ORGAN CHEM,D-30167 HANNOVER,GERMANY

来源：

TETRAHEDRON | 1997年 / 53卷 / 25期

关键词：

D O I：

10.1016/S0040-4020(97)00519-X

中图分类号：

O62 [有机化学];

学科分类号：

070303 ; 081704 ;

摘要：

Stereochemistry and mechanism of the title reaction have been investigated. The reaction proceeds well in the (S) series. In the epimeric (R) series a product spread is usually observed. In either series olefin configuration is lost (7 examples), consistent with a freely rotating exocyclic radical intermediate. An alpha-trimethylsilyl group at the olefinic terminus enhances the selectivity of the radical cascade Spectroscopic evidence and MMX calculations suggest that the tandem annulation products of the (S) series are favoured thermodynamically, being more stable than those of the (R) series. Pyranoside (R)G2a is frozen in a half chair conformation. (C) 1997 Elsevier Science Ltd.

引用

页码：8401 / 8420

页数：20

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