Summary Copper-catalyzed addition of organomagnesium halides to 2-(2,2-diethoxy- ethy1)oxirane (1) affords aldol acetals 2 which upon acid treatment undergo hydrolysis and dehydration to give a,[)-unsaturated aldehydes 7 with high yields. ... The problem of synthesizing a,a-unsaturated aldehydes (enals) by chain extension appears to be solved. An exhaustive literature survey would produce an almost infinite variety of methods. A closer look, however, reveals some ...