CLAISEN REARRANGEMENTS OF ENANTIOMERICALLY PURE C3-(ACYLOXY)-(E)-VINYLSILANES

被引:68
作者
SPARKS, MA [1 ]
PANEK, JS [1 ]
机构
[1] BOSTON UNIV,METCALF CTR SCI & ENGN,DEPT CHEM,BOSTON,MA 02215
关键词
D O I
10.1021/jo00010a046
中图分类号
O62 [有机化学];
学科分类号
070303 ; 081704 ;
摘要
The Ireland ester Claisen rearrangement of chiral (R)- and (S)-C3-(acyloxy)-(E)-vinylsilanes gives access to a wide range of alpha-chiral-beta-silyl-(E)-hexenoic acids with useful levels of diastereoselectivity for both the 2,3-syn and 2,3-anti diastereomers as illustrated in eqs 1 and 2. The vicinal diastereoselectivities for simple propionate esters rac-1b, (S)-1e, and (R)-1g can be varied from 1:12 to 16:1 (syn:anti) depending on reaction conditions. The employment of appropriately protected glycolate esters yields Claisen products with diastereoselectivities ranging from 23:1 (syn:anti), resulting from chelation control of enolate geometry, to 1:3.6 (syn:anti) via the use of a nonchelating, silicon-protecting group. The reaction of alpha-azido acetate (R)-1i is the first example of a Claisen rearrangement involving an alpha-azido ester and results in a new approach toward the asymmetric synthesis of alpha-amino acids. The assignment of relative stereochemistry based on the vicinal coupling constant data has been well documented.
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页码:3431 / 3438
页数:8
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