From Conjugated Tertiary Skipped Diynes to Chain-Functionalized Tetrasubstituted Pyrroles

A novel and metal-free method for the synthesis of chain-functionalized tetrasubstituted pyrroles from easily accessible tertiary skipped diynes, was reported. The method involved modular synthesis of chain functionalized tetrasubstituted pyrroles from easily available alkyl porpiolates, acid chlorides, and primary amine. The method used a primary amine for the nitrogen source and utilized the reactivity profile of tertiary 1,4-diyne scaffolds. The synthetic manifold in the method operated in the absence of metals and accelerated by the nucleophilic addition of a primary amine on the alkynoate function. Anti-Michael ring-closing hydroamination and a [3,3]-sigmatropic rearrangement helped to complete the process of producing pyrrole. It was observed during the process that the enamine formation is more faster than the enamine cyclization.