One-pot highly efficient synthesis of substituted pyrroles and N-bridgehead pyrroles by zinc-catalyzed multicomponent reaction.

A convenient zinc(II) chloride-catalyzed regioselective propargylation/amination/cycloisomerization process has been developed for the synthesis of substituted pyrrole derivatives from propargylic acetates, enoxysilanes and primary amines. Various aromatic and aliphatic propargylic acetates participate well in the reaction, providing the propargylation/amination/cycloisomerization products in good yields with complete regioselectivity. The one-pot multicomponent coupling reaction furnishes substituted pyrroles in high yields by circumventing the intermediates' isolation. Zinc(II) chloride acts as a multifunctional catalyst and catalyzes three mechanistically distinct processes in a single-pot. The protocol developed has been extended to the synthesis of N-bridgehead pyrroles containing polycyclic fragments.