2-Dimethoxyethyl 2-alkenoates are easily transformed into 2-(1-alkenyl)-1,3-dioxolan-2-ylium cations in situ on the action of titanium tetrachloride, which react with enamines to predominantly give syn Michael adducts in good yields. This is the first example of such a high syn-selectivity for the Michael reaction of α,β-unsaturated ester derivatives with ketone enolate equivalents.
2,2-二甲氧基乙基2-链烯酸酯在
四氯化钛的作用下很容易就地转化为2-(1-链烯基)-
1,3-二氧戊环-2-基阳离子,后者与烯胺反应主要生成顺式迈克尔加成物。良品率高。这是对α,β-不饱和酯衍
生物与酮烯醇盐当量的迈克尔反应具有如此高的顺选择性的第一个例子。