Pinku Kaswan

Oxidative Cross-Coupling of sp3- and sp2-Hybridized C–H Bonds: Vanadium-Catalyzed Aminomethylation of Imidazo[1,2-a]pyridines

The vanadium-catalyzed oxidative coupling of substituted 2-arylimidiazo[1,2-a]pyridines to N-methylmorpholine oxide, which acts as both a coupling partner and an oxidant, has been achieved. This reaction was applied to various substituted imidiazo[1,2-a]pyridine and indole substrates, resulting in yields as high as 90%. Mechanistic investigations indicate that the reaction may proceed via a Mannich-type process. This work demonstrates how oxidative aminomethylation can be used as a useful method to introduce tertiary amines into heterocycles, thus providing an alternative method for conventional Mannich-type reactions.

One-pot, three component tandem reaction of 2-aminopyridines, acetophenones and aldehydes: synthesis of 3-aroylimidazo[1,2-a]pyridines

A facile synthesis of 3-aroylimidazo[1,2-a]pyridine derivatives has been achieved through the one-pot, three-component tandem reaction of acetophenones, arylaldehydes and 2-aminopyridines in the presence of a catalytic amount of copper(II) chloride and air as the sole oxidant. The developed one-pot method is atom-economical and utilizes readily available precursors to offer highly functionalized N-fused imidazoles in moderate to good yields (26–82%). The presented tandem process is expected to proceed via crossed aldol condensation, Michael addition, copper catalyzed oxidative cyclization and subsequent aromatization.

Indium triflate catalyzed microwave-assisted alkenylation of methoxyphenols: synthesis of indenes and chromenes

In(OTf)3 catalyzed microwave-assisted alkenylation of methoxyphenols was investigated. Exclusive formation of either indenes or chromenes was observed depending on the position of the methoxy group on phenol. The structures of 1H-inden-4-ol derivatives (4a-e) and 4H-chromene derivatives (5a-j) were established by NMR ((1)H & (13)C) and high-resolution mass spectra, which were further supported by single crystal X-ray analysis of 4c and 5a.