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The photolysis of a variety of aromatic thiol esters was investigated in cyclohexane using a 254-nm light source.The photochemical reaction proceeds initially by cleavage of the S-acyl bond, giving rise to the corresponding aromatic thiyl radical and an acyl radical which sometimes decarbonylates. The resulting radicals recombine to give disulfides, sulfides, and hydrocarbons. Acyl radicals which are less prone to decarbonylation abstract hydrogen to form aldehydes. No photo-Fries rearrangement and a minor amount of Norrish type II cleavage were observed. Sulfide formation appears to be intermolecular.We found that the photolysis of 4-tolyl thiolacetate gave 4-tolyl disulfide and methyl 4-tolyl sulfide but no 4-toluenethiol nor any photo-Fries rearrangement.2 Subsequently, Bradshaw and coworkers3 reported the major products of the photolysis of phenyl thiolacetate to be phenyl disulfide, methyl phenyl sulfide, and thiophenol, which arises from secondary photolysis of phenyl disulfide without the intervention of solvent,4 plus minor amounts of the corresponding photo-Fries products.The purpose of this paper is to report the photochemistry of several aryl thiol esters in an effort to uncover partially the nature of the excited state responsible

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The reaction between benzonitrile N-sulfide, generated from the fluoride ion catalyzed elimination of two molecules of hydrogen fluoride from (benzy1imino)sulfur difluoride, and either methyl propiolate or 3-butyn-%one gave predominantly the 4-substituted isothiazole isomer. Comparison of the isothiazole isomer ratios found for the Nsulfide generated from iminosulfur difluoride and phenyloxathiazolone leads to the conclusion that hydrogen fluoride causes an increased amount of 4-substituted isothiazole. Molecular orbital calculations (CND0/2) show that the interaction of the HOMO of the N-sulfide and the LUMO of the acetylenes gives the 4-substituted isothiazole. The observation that the 5-carbon absorbs significantly downfield from the 4-carbon in the NMR spectra of isothiazoles allows the unambiguous assignment of regiochemistry of the isothiazoles.

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