Solvent effects on photocycloadditions of dibenzoylmethanatoboron difluoride with enol ethers

The photolysis of dibenzoylmethanatoboron difluoride (DBMBF2) in the presence of vinyl ethers in acetonitrile gave dimers of the latter from acid catalysis or electron transfer sensitization, but, it contrast, gave cycloaddition products in an efficient reaction in less polar solvents such as tetrahydrofuran (THF) and benzene.