Selective formation of five-membered heterocyclic products by anodic oxidation of alkyl isothiocyanates (RNCS) in dichloromethane and their thermal isomerization and decomposition

Isothiocyanates in the chemistry of heterocycles

“…Anodic oxidation of primary and secondary alkyl isothiocyanates in methylene chloride furnished iminodithiazolidinones 333 and thiadiazolidinethiones 334, their ratio being dependent on the length or bulkiness of the alkyl group in the isothiocyanate molecule. 317 Isomer 333 was favorable when R = Me and Et and exclusive for R = n-Pr, n-Bu, and cyclohexyl, but during separation by GLC at 150-200 °C, these were completely isomerized to 334, besides forming the corresponding N,N'-disubstituted carbodiimides (Scheme 32). 317 This anodic oxidation was also carried out in acetonitrile medium and it was observed that primary alkyl isothiocyanates furnished mainly five-membered heterocyclic products while tertiary ones afforded amides due to a-cleavage or isocyanates as a result of substitution of sulfur with oxygen.…”

“…317 Isomer 333 was favorable when R = Me and Et and exclusive for R = n-Pr, n-Bu, and cyclohexyl, but during separation by GLC at 150-200 °C, these were completely isomerized to 334, besides forming the corresponding N,N'-disubstituted carbodiimides (Scheme 32). 317 This anodic oxidation was also carried out in acetonitrile medium and it was observed that primary alkyl isothiocyanates furnished mainly five-membered heterocyclic products while tertiary ones afforded amides due to a-cleavage or isocyanates as a result of substitution of sulfur with oxygen. 318 Recently, cyclization, cv-cleavage, and substitution process in the anodic oxidation of alkyl isothiocyanates were reviewed.319 4. Conversion of Preformed Heterocycles to Other Rings As already mentioned, some heterocycles reacted with isothiocyanates to give other rings.…”