A multi pathway coupled domino strategy: I2/TBHP-promoted synthesis of imidazopyridines and thiazoles via sp3, sp2 and sp C-H functionalization

I₂/TBHP-promoted, one-pot, multi pathway synthesis of imidazopyridines and thiazoles has been achieved through readily available ethylarenes, ethylenearenes and ethynearenes. I₂/TBHP as an initiator and oxidant is used to realize the C-H functionalization of this domino reaction. Simple and available starting materials, wide range of functional group tolerance, high potential for drug activity of the products and application in production are the advantageous features of this method.

Facile synthesis of 3-substituted imidazo[1,2-a]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 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.

Iodine–NH4OAc mediated regioselective synthesis of 2-aroyl-3-arylimidazo[1,2-a]pyridines from 1,3-diaryl-prop-2-en-1-ones

An efficient, metal-free regioselective synthesis of 2-aroyl-3-arylimidazo[1,2-a]pyridines from 1,3-diaryl-prop-2-en-1-ones has been developed by their reaction with 2-aminopyridine in the presence of I₂/NH₄OAc.

Metal- and base-free synthesis of imidazo[1,2-a]pyridines through elemental sulfur-initiated oxidative annulation of 2-aminopyridines and aldehydes

An elemental sulfur-based metal- and base-free system enables oxidative imidazo[1,2-a]pyridine annulations.