(1 7) The photochemical conversion of 2-carbomethoxybenzocyclobutenone in methanol to dimethyl homophthalate may also proceed via an intermediate hemiketal: RJ Spangler and JH Kim, unpublished results.(18) P. Yates and R. 0. Loutfy, Acc. Chem. Res., 8, 209 (1975).(19) SP Pappas and JE Blackwell, Tetrahedron Lett., 3337 (1968).(20) G. Queguiner and A. Godard, CR Acad. Sci., Ser. C, 269, 1646