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Facile synthesis of 3-substituted imidazo[1,2-a]pyridines through formimidamide chemistry†‡
Rasapalli Sivappa,Vamshikrishna Reddy Sammeta,Yanchang Huang,James A. Golen,Sergey N. Savinov
RSC Advances Pub Date : 09/19/2019 00:00:00 , DOI:10.1039/C9RA05841A
Abstract

A facile entry to 3-aryl/alkenyl/alkynyl substituted imidazo[1,2-a]pyridines (3a–p, 6a–d & 9a–9e) has been developed from readily available benzyl/allyl/propargyl halides and 2-amino pyridines as substrates via formimidamide chemistry that is devoid of caustic or expensive reagents, such as transition metal complexes. Quantum chemical calculations performed to understand the underlying mechanism of the transformation revealed a preference for intramolecular Mannich-type addition over pericyclic 1,5-electrocyclization for the systems reported herein that enable a Baldwin allowed 5-exo-trig cyclization instead of a formally anti-Baldwin 5-endo-trig process.

Graphical abstract: Facile synthesis of 3-substituted imidazo[1,2-a]pyridines through formimidamide chemistry
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