Base‐Free Synthesis of S‐Alkyl Isothioureas Through Ring‐Opening Reaction of Sulfonium Salts with Isothiocyanates and Amines

A convenient and base-free three-component reaction has been developed for the synthesis of S-alkyl substituted isothioureas from cyclic sulfonium salts, isothiocyanates, and amines. This protocol provides an alternative avenue to access a series of S-alkyl substituted isothioureas in moderate to good yields through ring-opening reaction of aryl, alkenyl and alkynyl sulfonium salts. The present strategy features operational simplicity, good functional group tolerance, gram-scale synthesis and high reaction efficiency.