Thermal reaction of diastereomeric benzocyclobutenols. Evidence for reversible opening of 1,2-dihydrobenzocyclobutenols to hydroxy-o-xylylenes

Thermolysis of 1,2-dihydrobenzocyclobutenols 2a,b or 3a-c without solvent a t 120 degrees C gave a 1:1 mixture of 2a-c and 3a-c together with 3-hydroxy -2,2-dimethyl-1-(o-methylphenyl)alkan-1-ones 1a-c and o-methylisobutyrophen one 5. Thermolysis of 2a or 3a under the same conditions but at 150 degrees C gave only 5. Thermolysis of 2c or 3c in benzene-d(6) at 120 degrees C re sulted in clean interconversion between 2c and 3c. Thermolysis of 1,2-dihyd robenzocyclobutenols 2d-f or 3d-f without solvent at 150 degrees C gave a m ixture of 2d-f and 3d-f together with 3-acetoxy-2,2-dimethyl-1-(o-methylphe nyl)alkan-1-ones 1d-f and benzyl ketones 9a-c.