Studies on heterocyclic chemistry. Part 21. Reactions of 3-mercapto- and 3-acylthio-3-isothiazoline-5-thiones: ring transformations, a base-induced ring cleavage, and thiol-ester–thioxo-ester rearrangements

Abstract

Acylation of 4-aryl-3-mercapto-3-isothiazoline-5-thiones (1) with acid chloride in pyridine or alternatively with acid anhydride leads exclusively to 3-acylthio-4-aryl-3-isothiazoline-5-thiones (2). Reactions of (1) with reactive acetylenes afford 2-[aryl(thiocarbamoyl)methylene]-1,3-dithiole derivatives (3) whereas those of (2) with the acetylenes are accompanied by an S → N acyl migration giving N-benzoyl-[4,5-bis(methoxycarbonyl)-1,3-dithiol-2-ylidene]arylethanethioamides (4). ¹³C N.m.r. spectra and some chemical reactions of (3) and (4) are described. The ring-cleavage of (1) with base and the thiol-ester–thioxo-ester rearrangements of (2) induced by diazoalkane, alkyl iodide, or triethyloxonium tetrafluoroborate are also reported.