Thermal [2 + 2]cycloaddition of 1,1-dimethoxyalkenes to acetylenic esters
Abstract
[2 + 2]Cycloaddition of the 1,1-dimethoxyalkenes 1 to acetylenic esters, such as dimethyl acetylenedicarboxylate 2a and methyl propiolate 2b, occurs via 1,4-dipolar intermediates which, trapped by methyl propiolate and tert-butyl alcohol, give functionalized 3,3-dimethoxycyclobutenes 3, synthetic precursors to naturally occurring products and biologically active compounds.