Palladium-Catalyzed Multicomponent Coupling of Alkynes, Imines, and Acid Chlorides:  A Direct and Modular Approach to Pyrrole Synthesis

A new palladium-catalyzed method to prepare pyrroles directly from three basic building blocks-imines, alkynes, and acid chlorides-is described. This approach provides a straightforward method both to prepare pyrroles in one step and to diversify their structure by simple variation of any of the three starting materials. Mechanistic studies suggest that this process occurs via a complex series of eight individual steps, and this is discussed.