Catalytic Tandem Annulation Reaction for the Synthesis of Heterocycles

Abstract

Transition-metal catalyzed tandem processes have been extensively investigated as they are one of the most versatile reactions for the efficient, regioselective synthesis of complex organic molecules. Tandem cyclization reactions of o-alkynylanilines with aldehydes have been developed to afford quinoline derivatives. On the other hand, tandem cyclization reactions of ethyl 3-(2-(phenylethynyl)phenyl)propiolate with 3-methoxyphenol provided a facile route to a coumarin derivative. The combination of Pd(OAc)2 and p-TsOH and the combination of AuClPPh3/AgOTf and MsOH exhibited synergistic effect to improve the efficiency of these tandem cyclization reactions. Rational design of catalytic system and exquisite tune of catalysts and reaction conditions could modulate the reaction propensity and reaction pathway for the regioselective synthesis of quinoline and coumarin derivatives. These transition-metal-catalyzed tandem annulation reactions offer considerable advantages with regard to simplicity and high efficiency. More detailed investigations are needed to clarify the mechanism for the present reactions.