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

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...

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Bibliographic Details
Published in:RSC advances 2019-09, Vol.9 (51), p.29659-29664
Main Authors: Sivappa, Rasapalli, Sammeta, Vamshikrishna Reddy, Huang, Yanchang, Golen, James A, Savinov, Sergey N
Format: Article
Language:English
Subjects:
Aromatic compounds
Chemistry
Coordination compounds
Crystallography
Halides
NMR
Nuclear magnetic resonance
Organic chemistry
Pyridines
Quantum chemistry
Reagents
Substitutes
Substrates
Transition metal compounds
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Summary: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. A facile entry to 3-substituted imidazo[1,2- a ]pyridines from halides and 2-amino pyridines via formimidamide chemistry has been developed through a formal anti-Baldwin 5-endo-trig cyclization that becomes a thermally allowed 5-exo-trig cyclization.
ISSN:2046-2069
2046-2069
DOI:10.1039/c9ra05841a