Cu(OAc)₂–Et₃N mediated oxidative coupling of α-azido ketones with pyridinium ylides: utilizing in situ generated imines for regioselective synthesis of imidazo[1,2-a]pyridines

Abstract

Phenacyl azides were reacted with pyridinium ylides in the presence of Cu(OAc)2 (2 mol%) and Et3N utilizing molecular oxygen as a green oxidant to yield imidazo[1,2-a]pyridines in exclusive regioselectivity. Following the optimized protocol, 28 different fused heterocycles were synthesized in high yields (71-92%). In order to get mechanistic insight into the reaction, a few control experiments were carried out and the role of the copper salt was discussed.

One‐Pot Synthesis of Naphtho[1′,2′:4,5]imidazo[1,2‐a]pyridin‐5‐yl(aryl)methanones through Sequential Sonogashira Coupling/Alkyne–Carbonyl Metathesis

“…As part of our research interest to develop one‐pot operations for the synthesis of bioactive scaffolds, we wish to synthesize naphtho[1′,2′:4,5]imidazo[1,2‐ a ]pyridines with distinctive substitution patterns. This will be achieved by employing intramolecular ACM with imidazo[1,2‐ a ]pyridines substituted with formyl and alkyne functionalities at appropriate positions, which will be generated in‐situ from imidazo[1,2‐ a ]pyridine that bears formyl and bromo groups through Sonogashira cross‐coupling in a one‐pot operation.…”

Copper-Catalysed Tandem Synthesis of Substituted Quinazolines from Phenacyl Azides and O -Carbonyl Anilines

“…A possible mechanism for the synthesis of substituted quinazolines was proposed in Scheme according to the recent literature reports ,. Initially, phenacyl azides loses nitrogen (‐N 2 ) under Cu(OAc) 2 /Et 3 N catalytic system to give copper chelated imine 4 .…”

Synthesis of C3-Cyanomethylated Imidazo[1,2-a]pyridines via Ultrasound-Promoted Three-Component Reaction under Catalyst- and Oxidant-Free Conditions

“…Over the years, as a concise and efficient synthesis strategy, multicomponent reactions (MCRs) have been one of the hot spots in constructing functionalized heterocycles, 7 which were also successfully used in the formation of C3-functionalized imidazo[1,2- a ]pyridines, 8 such as C3-amination, 8` c d e C3-alkylation, 8f–h C3-cyanation, 8i C3-arylation, 8j C3-carbonylation, 8k C3-esterification, 8l C3-sulfuration, 8m C3-selenylation, 8n and C3-aminomethylation, 8o etc. To the best of our knowledge, constructing C3-cyanomethylated imidazo[1,2- a ] pyridines in one step through MCRs has not been explored.…”