Enantioselective Lewis acid-catalyzed Mukaiyama-Michael reactions of acyclic enones.: Catalysis by allo-threonine-derived oxazaborolidinones

被引:41
作者
Wang, XW [1 ]
Adachi, S [1 ]
Iwai, H [1 ]
Takatsuki, H [1 ]
Fujita, K [1 ]
Kubo, M [1 ]
Oku, A [1 ]
Harada, T [1 ]
机构
[1] Kyoto Inst Technol, Dept Chem & Mat Technol, Sakyo Ku, Kyoto 6068585, Japan
关键词
D O I
10.1021/jo035379x
中图分类号
O62 [有机化学];
学科分类号
070303 ; 081704 ;
摘要
allo-Threonine-derived O-aroyl-B-phenyl-N-tosyl-1,3,2-oxazaborolidin-5-ones 1g,n catalyze the asymmetric Mukaiyama-Michael reaction of acyclic enones with a trimethylsilyl ketene S,O-acetal in high enantioselectivity. A range of alkenyl methyl ketones is successfully employed as Michael acceptors affording ee values of 85-90% by using 10 mol % of the catalyst. The use of 2,6-diisopropylphenol and tert-butyl methyl ether as additives is found to be essential to achieve high enantioselectivity in these reactions. The effects of the additives are discussed in terms of the retardation of an Si+-catalyzed racemic pathway, which seriously deteriorates the enantioselectivity of asymmetric Mukaiyama-Michael reactions. A working model for asymmetric induction is proposed based on correlation between catalyst structures and enantioselectivities.
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页码:10046 / 10057
页数:12
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