Introduction of a bipyridine-based molten salt containing cobalt as anefficient and reusable catalyst for the Biginelli reaction

The research on one-pot multicomponent reactions has been an area of interest for thesynthesis of N-containing heterocyclic scaffolds, such as ۳,۴-dihydropyridin-۲-۱H-(ones)/۳,۴-dihydropyridin-۲-۱H-(thiones) (DHPMs) and their derivatives. These heterocyclic compounds,particularly those with a DHPM core, have proven to have significant applications in biologicaland pharmacological fields, such as antibacterial, antihypertensive, calcium channel modulation,antiviral, antitumor, antifungal, anti-tubercular, mitotic kinesin Eg۵ inhibition, anti-HIV, anti-HSV, and anti-inflammatory [۱-۲]. One of the most effective ways to synthesize DHPMs is theBiginelli reactions, which involves the condensation of an aldehyde,  β-ketoester, and urea understrongly acidic conditions. Despite several improved methods using different catalysts and reactionmedia to increase the yield and purity of the synthesized products, they suffer from disadvantagessuch as organic solvent use, long reaction times, low yields, high catalyst loading, and hardseparation routes [۳]. A new Lewis acidic molten salt based on bipyridine has been developed andused in this study to promote the synthesis of ۳,۴-dihydropyridin-۲-۱H-(ones)/۳,۴-dihydropyridin-۲-۱H-(thiones) compounds in a simple manner (Scheme۱). The advantages of using this catalystinclude ease of separation and high yield of products achieved in a shorter time.

Keywords:

One-pot , DHPMs , Dihydropyrimidine , Biginelli , Multicomponent , Molten salt