一锅法合成β-三氟甲基-α-甲基-α、β-不饱和酸酯

One-pot Synthesis of β-Trifluoromethyl-α-methyl-α,β-unsaturated Esters

正丁基锂在-78℃攫取(α-烷氧羰基)乙基膦酸二乙酯(1)的活泼氢得到碳负离子2,其进攻三氟醋酸酐产生三氟乙酰基膦酸酯(3);不经过分离,直接用Grignard试剂进攻三氟乙酰基膦酸酯(3),由HWE反应选择性地合成了以Z-式为主的β-三氟甲基-α-甲基-α、β-不饱和酸酯(4),按1计,三步反应的总收率为59%～92%,Z-构型反应产物是主要产物。

Diethyl （α-alkoxycarbonylethyl）phosphonate （1） was treated with n-butyllithium in tetrahydrofuran at -78℃. The resulting carbanion 2 reacted with trifluoroacetic acid anhydride to afford trifluoroacylated phosphonate intermediate （3）, and without isolation, 3 was attacked by Grignard reagents via HWE reaction giving β- trifluoromethylated-α-methyl-α,β-unsaturated esters （4） in totally 59%-92% yields with dominantly Z- stereoselectivity.