Reactions of cyclohexadienes. Part XII. Some dienamines and dimethyl acetylenedicarboxylate

Abstract

Reaction of some N-(cyclohexa-1,3-dienyl)morpholine derivatives with dimethyl acetylenedicarboxylate gives rise initially to cyclobutene derivatives by reaction with the enamine double bond. Whether these adducts are stable, or convertible into the isomeric cyclo-octatrienes, depends on the presence and nature of a substituent at the 4-position of the cyclohexadiene. Attempted dehydrogenation of dimethyl 6-morpholinobicyclo[4,2,0]octa-2,7-diene-7,8-dicarboxylate (2; R = H) led surprisingly to dimethyl 3-morpholinophthalate.