CRYSTAL-STRUCTURE CORRELATIONS IN THE PHOTOCHEMISTRY OF DIMETHYL 9-CHLOROMETHYL-9,10-DIHYDRO-9,10-ETHENOANTHRACENE-11,12-DICARBOXYLATE

{A study of the photochemistry of the title 9-chloromethyldibenzobarrelene-11,12-diester (1) reveals the formation of semibullvalene derivatives [(2) and (3)] in acetone solution, with additional noveL photoproducts [two isomers of dimethyl 5-chloro-10-methylene-5,5a,10,10a-tetrahydroindeno[2,1-a]-indene-5a,10a- dicarboxylate; (4) and (5)] in other solvents, and especially in solid-state photolysis. The structures of (1), (4) and (5) have been determined by X-ray crystal analyses. Crystal data: T = 294 K, Cu Kalpha