Thermally Induced Cyclobutenone Rearrangements and Domino Reactions

Four thermal-rearrangement pathways and a domino reaction leading to quinones arise from the thermolysis of cyclobutenones. The course of vinylcyclobutenone rearrangements is dictated by the nature of the substituent, R (see scheme): a cyclopentenone arises when R is an electron-rich alkene. In other cases thermolysis gives a cyclohexadienone, which may collapse with elimination to form a quinone, or tautomerize into a hydroquinone or cyclohexenedione.