Stereoselective allylation of 2-formyl amides or 3-oxo amides has been studied. Treatment of 2-formyl-N,N-dimethylpropanamide (1a) with allylzinc bromide gave 3-hydroxy-2,N,N-trimethyl-5-pentenamide as a stereoisomeric mixture (2a : 3a = 63 : 37). Meantime, the reaction of 1a with allyltrimethylsilane in the presence of Lewis acid such as EtAlCl2 or BF3·OEt2 afforded threo-adduct 2a exclusively. Whereas treatment of 2-benzoyl-N,N-dimethylpropanamide (PhCOCH(Me)CONMe2) with allylzinc bromide provided erythro-3-hydroxy-2-methyl-3-phenyl-5-hexenamide with high stereoselectivity, allylation with allylsilane in the presence of a catalytic amount of n-Bu4NF afforded stereoisomeric threo hydroxy amide exclusively.
2-甲酰胺或3-氧代酰胺的立体选择性烯丙基化反应已被研究。2-甲酰基-N,N-二甲基丙酰胺(1a)与
烯丙基溴化锌反应得到3-羟基-2,N,N-三甲基-5-
戊烯酰胺的立体异构体混合物(2a : 3a = 63 : 37)。同时,1a与烯丙基三甲基
硅烷在Lewis酸如EtAlCl2或
BF3·OEt2存在下反应,仅得到苏式加合物2a。然而,2-苯甲酰基-N,N-二甲基丙酰胺(PhCOCH(Me)CONMe2)与
烯丙基溴化锌反应,以高立体选择性得到赤式3-羟基-2-甲基-3-苯基-5-己烯酰胺,在催化量n-Bu4NF存在下与烯丙基
硅烷反应则仅得到立体异构的苏式羟基酰胺。