One-Pot Synthesis of Highly Functionalized Bicyclic Imidazopyridinium Derivatives in Ethanol

A concise and eco-friendly
route for the synthesis of highly functionalized
bicyclic pyridinium derivatives (3) via a one-pot reaction
of chromone-3-carboxaldehydes (1) and N-benzyl nitro ketene aminals (NBNKAs) (2) under reflux
in ethanol media has been developed. The targeted compound was efficiently
obtained by filtration without further post-treatment. In the one-pot
two step reaction, CC and CN bonds were constructed,
while at the same time one CO bond was cleaved. This protocol
represents a valuable route to obtain highly functional bicyclic pyridinium
derivatives in a concise, rapid, and practical manner. The reaction
is particularly attractive due to features such as low cost, mild
conditions, atom economy, high yield, using biocompatible solvent,
and potential biological activity of the product.