Selective Formation of Five-Membered Heterocyclic Products by Anodic Oxidation of Alkyl Isothiocyanates (RNCS) in Dichloromethane and Their Thermal Isomerization and Decomposition

Article abstract of DOI:10.1021/jo00243a028

Anodic oxidation of primary and secondary alkyl isothiocyanates (RNCS) in dichloromethane yielded two isomers of five-membered heterocyclic products, 4-alkyl-5-(alkylimino)-1,2,4-dithiazolidine-3-one 2 and 2,4-dialkyl-5-oxo-1,2,4-thiadiazolidine-3-thione 3.Their relative ratio was found to be depedent on the length or bulkiness of the alkyl group in RCNS.Isomer 2 was favorable for R = Me and Et and exclusive for R = n-Pr, n-Bu, and cyclohexyl.Upon GLC injection (at 150-200 deg C), compounds of type 2 isomerized completely to 3 (when R = Me, Et), mostly to 3 and partially decomposed to RN=C=NR (11) (when R = n-Pr, n-Bu), and exclusively decomposed to 11 for R = cyclohexyl.Tertiary RNCS did not yield cyclic products but instead underwent chlorination to substitute a hydrogen (or "NCS" group) by chlorine.Plausible mechanistic schemes are suggested and discussed.