Abstract
A one-pot pseudo-three-component reaction strategy has been designed for synthesizing
all-carbon-functionalized hexasubstituted N ,1-dimethyl-6-(methylsulfanyl)-3,5-dinitro-1,4-dihydropyridine-2-amines under neat
conditions using inexpensive, readily available, natural, biodegradable lemon juice
as a catalyst. The acidic reaction environment induced by lemon juice provided a superior
catalytic performance, with a high reaction rate and high product yields, to those
of a pool of Lewis and Brønsted acid catalysts. The wide substrate scope and functional-group
tolerance permitted diversity creation with electronic and structural variations in
a robust and operationally simple manner. The recoverability/reusability of the lemon
juice catalyst and the easy purification of the end products by precipitation/filtration
avoid the need for column chromatography or hazardous organic solvents and confirm
that this is an environmentally benign sustainable technology. Moreover, a gram-scale
operation and chemical modifications of the final products demonstrated some promising
advantages.
Key words 1,4-dihydropyridines - acid catalyst - solvent-free reaction - green chemistry - lemon
juice
