REACTION OF PHOSPHONIUM YLIDES WITH 3,5-DI-TERT-BUTYL-1,2-BENZOQUINONE

The reactions of quinone 1 with several Wittig reagents have been studied. When 1 was added to excess of 2, the corresponding 1, 1, 2, 2-tetrabromocyclobutene derivative 4 was obtained. Reaction of 1 with moderate-stabilized ylides 5a, b at room temperature afforded the monosubstituted α,β-unsaturated esters 6, while carrying out the reaction in boiling benzene led to the formation of coumarin-derivatives 8. On the contrary, the reaction of 1 with resonance-stabilized ylides 5c, d takes place, only at higher temperature to give disubstituted α,β-unsaturated ketones 9. © 1991, Taylor & Francis Group, LLC. All rights reserved.