Collect. Czech. Chem. Commun. 1986, 51, 2002-2012

A study of photocyclization of O-alkyl N-(3-chloro-2-benzo[b]thienocarbonyl)monothiocarbamates

Peter Kutschy, Ján Imrich, Juraj Bernát, Pavol Kristian and Iveta Fedoriková

Department of Organic Chemistry and Biochemistry, Faculty of Natural Sciences, Šafárik University, Moyzesova 11, 041 67 Košice


The O-alkyl N-(3-chloro-2-benzo[b]thienocarbonyl)monothiocarbamates prepared by the reaction of 2-isothiocyanatocarbonyl-3-chlorobenzo[b]thiophene with methanol, ethanol, 1-propanol, and 2-propanol are cyclized on irradiation with light of the wavelength above 300 nm to give high yields (80-90%) of 2-alkoxy-4H-benzo[b]thieno[2,3-e]-1,3-thiazin-4-one derivatives. From the absorption and emission spectra of the starting compounds as well as from a study of model compounds and influence of the reaction conditions it is presumed that the investigated intramolecular photosubstitution of chlorine by sulphur proceeds from the first singlet excited state (π, π*) by a radical mechanism through the phase of radical complex formation.