Hydrogen bonds in N-(3-chloro-2-benzo[b]thienocarbonyl)- and N-(2-benzo[b]thienocarbonyl)-N'-monosubstituted thioureas

Abstract

N-(3-Chloro-2-benzo[b]thienocarbonyl)-N'-monosubstituted thiourea derivatives undergo photocyclizations with lower yields than those obtained from analogous N',N'-disubstituted derivatives. This decreased reactivity is caused by the existence of a six-membered cyclic form with the very strong hydrogen bond NH···O=C. The possibility of formation of various conformers has been found with N-(2-benzo[b]thienocarbonyl)-N'-monosubstituted thiourea derivatives as a consequence of the rotation around the C(2)-C(O) connecting line.