Unprecedented Synthesis of 2H,6H-1,5-Dithiocines Reinvestigated: A Structural Corrigendum Revealing Isothiazole-3(2H)-thiones

Dedicated to Professor Ernst Schaumann

Abstract

The synthesis of postulated 2H,6H-1,5-dithiocines from isonitriles and acetylenedicarboxylates or dibenzoylacetylene in the presence of elemental sulfur was repeated. The products do not possess the structure of eight-membered sulfur heterocycles, but isothiazole-3(2H)-thiones were formed instead. This structural corrigendum was confirmed not only by a critical consideration of the ¹³C NMR spectroscopic data and by the correction of the MS spectra and the values of the elemental analyses but also by X-ray crystallographic structure determination. Several reaction mechanisms are discussed to explain the generation of the observed isothiazole-3(2H)-thiones.

Key words

alkynes - heterocycles - multicomponent reaction - nucleo­philic addition - ring closure - spectroscopy - structure analysis - sulfur

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