The conjugate addition of activated propargylic alcohols to alkyl propiolates is shown to be catalyst-dependent. Whereas trialkylamines catalyze the expected 1,4-adition of the alcohol on the alkynoate to give the β-alkoxyacrylate derivative, the trialkylphosphine-catalyzed reaction affords densely functionalized bicyclic hexahydrofuro[2,3-b]furan derivatives. A mechanistic proposal for the phosphine-catalyzed addition of alcohols to alkyl propiolates according with these observations is presented.
活化
丙炔醇与
丙炔酸烷基酯的共轭加成显示出催化剂依赖性。
三烷基胺催化醇与炔酸盐发生预期的 1,4 加成反应,生成δ-烷氧基
丙烯酸酯衍
生物,而三烷基膦催化的反应则生成致密官能化的双环
六氢呋喃并[2,3-b]呋喃衍
生物。根据这些观察结果,提出了膦催化醇与烷基
丙炔酸酯加成反应的机理建议。