Diversity‐Oriented Metal‐Free Synthesis of Nitrogen‐Containing Heterocycles Using Atropaldehyde Acetals as a Dual C3/C2‐Synthon

Abstract

A highly efficient and elegant diversity‐oriented reaction paradigm employing atropaldehyde acetals as new dual C2/C3 synthons was developed under metal‐free conditions using glycine esters as the counterpart reagents, which allowed rapid synthesis of two important nitrogen‐containing heterocycles, pyrrolo[1,2‐a]quinolines and 3,5‐diarylpyridines. The divergent products are subtly controlled by the manipulation of the substitutional groups of glycine esters. When a N‐arylglycine ester was used, pyrrolo[1,2‐a]quinolines can be formed through cascade oxidative C−C cleavage/multiple cyclization. Instead, N‐benzylglycine ester as the counter‐reagent led to the synthesis of 3,5‐diarylpyridines via two key C−N cleavages. Mild conditions, broad substrate scope, scalability and environmentally acceptable organic solvents rendered this method practical and attractive.