Synthesis and photooxygenation of 3-(-substituted phenyl)-3a,8a-dihydro--cyclohepta[d]isoxazoles: facial selectivity.

Two 3-(-substituted phenyl)-3a,8a-dihydro-4-cyclohepta[d]isoxazoles were synthesized by 1,3-dipolar cycloaddition of the corresponding nitrile oxides with cycloheptatriene. Two endoperoxides were synthesized as facially selective and single products in high yields (93%-95%) from the reactions of isoxazole derivatives with singlet oxygen. The exact configurations of the endoperoxide with a methyl group in the phenyl ring and the diol synthesized from it were confirmed by X-ray analysis.