Halogenation of n-heteroaromatic hydroxy compounds with pph3/halogenating agent

Abstract

Two new methodologies utilizing conventional heating and microwave (MW) heating for halogenation of N-heteroaromatic hydroxy compounds using PPh₃ and halogenating agent have been developed. The optimal conditions for the synthesis of N-heteroaromatic halides including type of halogenating agent, amount of reagents, reaction time and solvent were explored. In the case of conventional heating, Cl₃CCN or CBr4 in combination with PPh₃ approved to be a highly reactive reagent for the conversion of N-heteroaromatic hydroxy compounds to the corresponding halides in refluxing toluene for 4 h. On the other hand, Cl₃CCN, Cl₃CCOCCl₃ and CBr₄ with PPh3 could convert N-heteroaromatic hydroxy compounds and coumarin derivatives to desired halides in high yields at 150°C for 20 min under MW irradiation.