1,4-dimethoxy-1,3-butadiene as a Donor Diene in Diels-Alder Cycloadditions

Article abstract of DOI:10.1021/jo00147a007

The title compound (DMBU) is a useful diene in <4 + 2> cycloadditions.Since DMBU is readily obtained in two steps from 1,4-dihydroxy-2-butyne, it should be regarded as an inexpensive and abundant starting material.Diels Alder products were obtained from DMBU and the dienophiles, dimethyl acetylenedicarboxylate, ethyl propiolate, benzyne, fumaronitrile, tetracyanoethene, maleic anhydride, 1,2-dibenzoylethene, diethyl azodicarboxylate, and four 1,4-quinones.The aromatization of some of these products was studied.As determined by gas chromatography and 1H NMR, DMBU is obtained as three isomers Z,Z/Z,E/E,E = (60 +/-3):(34 +/- 3):(6 +/- 2).While the Z,Z form is less reactive, the Z,E and E,E isomers react with tetracyanoethene at rates similar to that of 1-methoxy-1,3-butadiene.