Microwave‐Assisted C‐2 Direct Alk­enylation of Imidazo[4,5‐b]pyr­idines: Access to Fluorescent Purine Isosteres with Remarkably Large Stokes Shifts

Abstract

AbstractWe describe herein the first C‐2 direct alkenylation of the valuable 3H‐imidazo[4,5‐b]pyridine promoted by microwave‐assisted Pd/Cu co‐catalysis. The reaction is rapid and compatible with a wide range of functional groups either on the imidazo[4,5‐b]pyridine ring or on the styryl bromides thereby leading to the isolation of 23 compounds with moderate to good yields. The relevance of this method is demonstrated by its application to the synthesis of new cross‐conjuguated push–pull 2‐vinyl‐ and 2‐alkynylimidazo[4,5‐b]pyridines characterized by satisfactory fluorescence quantum yields and remarkable solvatofluorochromic properties.