Cooperative action between Iron(III) chloride and diorganyl dichalcogenides for the cyclization of N-(ortho-Alkynyl)aryl-pyrroles

Abstract

We report the ability of iron(III) chloride and diorganyl dichalcogenides to promote de cyclization of N -( ortho -alkynyl)aryl-pyrroles leading to 5-(organochalcogenyl)pyrrolo[1,2- a ]quinolines. The combination of diorganyl dichalcogenides and iron(III) chloride was crucial for the cyclization reaction to occur because neither the iron salt nor diorganyl diselenide alone were able to promote the cyclization. The effects of solvent, temperature, reaction time, and stoichiometry on the efficiency of cyclization reactions were investigated. The standard reaction conditions were compatible with many functional groups in the substrates, such as methyl, chlorine, and methoxy. In addition, under these conditions, not only diaryl, but also dialkyl dichalcogenides have been cyclized in moderate to good yields. The 5-(organochalcogenyl)pyrrolo[1,2- a ]quinolines prepared underwent a Suzuki cross-coupling reaction with boronic acids under palladium catalyze to give the cross-coupled products in good yields.