4,6-dimethyl-o-quinone methide and 4,6-dimethylbenzoxete

4,6-Dimethyl-o-quinone methide (4) was produced by FVP of alcohol 3 or of t he trimer 6 and matrix isolated in Ar at 7.6 K. Photolysis of 4 with long w avelength light (>345 nm) at this temperature afforded 4,6-dimethylbenzoxet e (5), which was observable up to room temperature in the solid state in th e absence of water. 5 can be converted back to 4 by UV irradiation at 254/1 90 nm. Quantum chemical calculations on the thermal interconversion of 4 an d 5 indicate activation barriers of the order of 40 kcal/mol for 4 --> 5, a nd 30 kcal/mol for 5 --> 4. The dimer, trimer, and tetramer (8, 6, and 7) o f 4 are characterized.