Absence of the alleged retardation of the Diels–Alder reaction for dienes bearing a neighbouring hydroxy substituent

Abstract

Contrary to earlier observations the diene 1 reacts readily in Diels–Alder additions. With N-methylmaleimide the stereoisomeric adducts 10a and 10b are formed in equal quantities. With malefic anhydride, ring-opening accompanies adduction to give 11 and two stereoisomers of gross structure 12. Dienes 1, 9 (X = OMe) and 9 (X = H) react at similar rates with N-methylmaleimide, discounting the alleged intramolecular retardation due to through space interaction between the hydroxy group and the diene system.