INTRAMOLECULAR CYCLIZATION OF [O-(ARYLTHIO)PHENYL]ETHENES - SYNTHESISAND CRYSTAL-STRUCTURE OF 1-ARYLBENZO[B]THIOPHENIUM SALTS

Novel 1-arylbenzo[b]thiophenium salts (4) are prepared by bromine-indu ced intramolecular cyclization of [o-(arylthio)phenyl]ethenes (3). The substituent and solvent effects on the formation of the 1-arylbenzo[b ]thiophenium salts 4 are described. The reaction with iodine monochlor ide provides the improved yields of 2-unsubstituted and 2-methyl-1-phe nylbenzo[b]thiophenium salts 4. The single crystal structure of 1,2,3- triphenylbenzo[b]thiophenium perchlorate (4 b: X = ClO4) shows that th e bonds around the sulfur atom are arranged pyramidally. The sulfur-ca rbon bond length related to the non-fused phenyl ring is 1.784 angstro m and the S-C bond lengths in the five-membered ring are 1.762 and 1.7 90 angstrom. The bond angles around sulfur are 92.1, 103.1, and 107.0- degrees. The relatively short interatomic distance (3.092 angstrom) be tween the sulfur and the oxygen of the perchlorate anion is observed.