A RING EXPANSION PROCEDURE BASED ON THE TANDEM DEALKOXYCARBONYLATION MICHAEL ADDITION-REACTION

被引：9
作者：
BUNCE, RA
SCHILLING, CL
机构：
[1] Department of Chemistry, Oklahoma State University, Stillwater
来源：
JOURNAL OF ORGANIC CHEMISTRY | 1995年 / 60卷 / 09期
关键词：
D O I：
10.1021/jo00114a024
中图分类号：
O62 [有机化学];
学科分类号：
070303 ; 081704 ;
摘要：
A three-step ring expansion procedure has been developed to convert methyl alpha,alpha-dialkyl-1-cyclopenteneacetates to highly functionalized cyclohexaneacetic esters. The procedure involves (1) ozonolytic double bond cleavage, (2) chemoselective Wittig olefination of the aldehyde carbonyl of the resulting keto aldehyde, and (3) tandem dealkoxycarbonylation-Michael addition to close the ring. The transformation proceeds best when the a-carbon of the starting acetate is quaternary, and thus, the method is unique in yielding hindered 2,2-dialkyl-3-oxocyclohexaneacetic esters. The reaction sequence is easily performed, and overall yields of 40-50% are readily achieved. The synthetic and mechanistic details of this process as well as optimization studies are presented. An analogous five-membered cyclization process was also investigated. Tandem dealkoxycarbonylation-Michael addition of 1-ethyl methyl (E)-7,7-dimethyl-6-oxo-2-octenedioate was found to afford a 24% isolated yield of ethyl 2,2-dimethyl-3-oxocyclopentaneacetate by a disfavored 5-[enolendo]-exo-trig process.
引用
收藏
页码：2748 / 2752
页数：5
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