Cerium (III) Chloride as a Catalyst in the Clauson-Kaas Reaction: Synthesis and Reactivity of N-Aryl-2-thiocyanatopyrroles

A new and efficient methodology for the Clauson-Kaas synthesis of N-aryl pyrroles, employing CeCl3.7H2O as catalyst, was developed. The transformation was performed in acetonitrile under reflux, using conventional heating and microwave irradiation. Employing NH4SCN/Oxiall as a new thiocyanating system for the so obtained N-aryl pyrroles, the synthesis 1-aryl-2-thiocyanato-1Hpyrroles was also successfully accomplished. The latter served as starting materials for the high-yielding NaBH4-mediated preparation of 1,2-bis(1-(aryl)-1H-pyrrol-2-yl)disulfides and the phase transfer-mediated synthesis of 1-aryl-2-(trichloromethylthio)-1H-pyrroles.