The DielsAlder reactions of quinone imine ketals

Abstract

N-Benzoyl- and N-arylsulfonyl-p-benzoquinone-mono-imine ketals (QIKs) undergo smooth Diels–Alder cycloadditions with typical 1,3-butadienes to yield the expected endo adducts. Treatment with catalytic acid rapidly converts the adducts to dihydronaphthalenes. The N-benzoyl derivatives require high pressures for cycloadditions while the N-tosyl and N-nosyl derivatives proceed under thermal (ambient pressure) conditions. In all cases the cycloadditions are completely regioselective.Key words: Diels–Alder, quinone imine ketal, hyperbaric chemistry.