Regio- and stereo-chemical aspects of [2 + 2] photocycloaddition between 1-benzoylindoles and olefins

The regio- and stereo-selectivities in the [2 + 2] photocycloaddition of a series of 1-benzoylindoles with vinyl acetate and methyl acrylate have been investigated. With some exceptions, the 1 -benzoylindoles gave exclusively or predominantly the corresponding 1-acetoxy-3-benzoyl and 3-benzoyl-1-methoxycarbonyl-1,2,2a,7b-tetrahydro-3H-cyclobut[b]indoles as mixtures of stereoisomers.