Diels-Alder cycloadditions: 3-(p-toluenesulfonyl)-2-propenal as dienophile

The cycloadditions of 3-(p-toluenesulfonyl)-2-propenal with cyclopentadiene, 1,3-cyclo-hexadiene, 1-methoxy-1,3-cyclohexadiene, 1-(trimethylsilyloxy)-1,3-butadiene, or 1,3-diphenyliso-benzofuran have been easily carried out at room temperature in the absence of catalyst. In contrast, furan has led to a Michael-type addition. The basic elimination of the sulfonyl moiety of a cyclo-adduct has shown that this dienophile is a synthetic equivalent of propynal.