[2,3]-THIA-WITTIG REARRANGEMENTS PROCEEDING WITH COMPLETE INVERSION OR WITH PARTIAL LOSS OF CONFIGURATION AT THE CARBANIONIC CENTER

被引:31
作者
BRICKMANN, K [1 ]
BRUCKNER, R [1 ]
机构
[1] UNIV WURZBURG, INST ORGAN CHEM, HUBLAND, W-8700 WURZBURG, GERMANY
来源
CHEMISCHE BERICHTE-RECUEIL | 1993年 / 126卷 / 05期
关键词
ALPHA-ALKYLTHIO STANNANES; WITTIG REARRANGEMENT; CONFIGURATIONAL STABILITY; ALPHA-LITHIO SULFIDES; 2,3] REARRANGEMENT;
D O I
10.1002/cber.19931260524
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Two pairs of diastereomeric gamma-(benzyloxy)-alpha-(tributylstannyl) sulfides (anti- and syn-13, anti- and syn-30) were prepared. nBuLi induced tin/lithium exchange in each of these compounds furnished alpha-lithiated sulfides which underwent 12,31-thia-Wittig rearrangements in THF at -78-degrees-C within 30 min. Competing [1,2]-thia-Wittig rearrangements were not observed, not even starting from stannyl sulfides 30 where the [2,3] shift requires the intermediacy of lithium thiolates 32 in which the aromaticity of a benzene ring is given up. The homoallyl thiols syn- and anti-19 were formed stereoselectively starting from the allylthio stannanes anti- and syn-13, respectively. This implies that the underlying thia-Wittig rearrangements are stereospecific and proceed with inversion of configuration at the carbanionic center, and that the lithio sulfides anti- and syn-18 formed in the course of these reactions are configurationally stable until they rearrange. The benzylthio stannanes anti- and syn-30 rearranged with low stereoselectivity. They furnished the benzyl thiols 33 as 71:29 and 28:72 mixtures of diastereomers, respectively. This means that the lithio sulfide intermediates involved in the latter rearrangements suffer some epimerization anti-31 reversible syn-31 prior to the sigmatropic bond shift.
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页码:1227 / 1239
页数:13
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