A convenient method for the synthesis of (Z)-α-haloacrylates: Lewis base-catalyzed carbonyl olefination using α-halo-C,O-bis(trimethylsilyl)ketene acetals
synthesis of (Z)-α-haloacrylates from variousaldehydes that uses α-halogenated ethyl-C,O-bis(trimethylsilyl)keteneacetals in the presence of a Lewis base catalyst such as acetate salts was established. This procedure gives the corresponding α-halo-α,β-unsaturated esters in high yields with excellent stereoselectivity from E/Z mixtures of ketene silyl acetals under mild conditions.
α-Hypervalent Iodine Functionalized Phosphonium and Arsonium Ylides and Their Tandem Reaction as Umpolung Reagents
作者:Zhizhen Huang、Xiaochun Yu、Xian Huang
DOI:10.1021/jo026077i
日期:2002.11.1
iodine functionalized phosphonium and arsonium ylides 2 can be used as umpolung ylides to react with nucleophiles to give alpha-heteroatom substituted ylides 4 in good yields. The nucleophilic substitution-Wittig tandem reaction of 2 can occur smoothly to provide an efficient method for the synthesis of (Z)-alpha-halo-alpha,beta-unsaturated enoates or enones 6, stereoselectively.