<scp>Groebke–Blackburn–Bienaymé</scp> multicomponent reaction coupled with unconventional <scp>Pictet–Spengler</scp> cyclization for the synthesis of imidazo[4,5‐<i>b</i>]pyridine fused polycyclic heterocycles
Rahul Singh, Ravinder Kumar, Manpreet Kaur, Madhuri T. Patil, Subash Chandra Sahoo, Deepak B. Salunke
Abstract
Abstract A diverse library of fused tetracyclic and pentacyclic imidazo[4,5‐ b ]pyridine scaffolds was synthesized using an unconventional strategy, involving Groebke–Blackburn–Bienaymé (GBB) multicomponent reaction coupled with Pictet–Spengler (PS) cyclization. The reaction strategy involves the use of 2‐aminoazine, aldehyde, and 1,1,3,3‐tetramethyl butyl isocyanide in the GBB reaction followed by the dealkylation to generate a free amine, which on PS cyclization with another aldehyde generated a fused polycyclic heterocycle. A small set of 15 diverse polycyclic heterocycles were synthesized and their structures were confirmed by 1 H NMR, 13 C NMR, and mass spectrometric analyses. In addition, a single‐crystal X‐ray diffraction of one of the library members established the three‐dimensional structure of the polycyclic skeleton.