Diels-Alder additions of dimethyl acetylenedicarboxylate to sterically hindered cyclohexa-2,4-dienones. Formation and X-ray structure analysis of stereoisomeric bicyclo[2.2.2]octadienones

Abstract

The Diels-Alder addition of dimethyl acetylenedicarboxylate to sterically hindered 2,4-cyclohexadienones (spiro-quinol ethers) gives rise to stereoisomeric bicyclo[2.2.2]octadienones. The structures of three of these have been elucidated by single-crystal X-ray diffraction methods and their 1H n.m.r. and electronic absorption spectral properties are reported.