Alginic acid: a highly efficient renewable and heterogeneous biopolymeric catalyst for one-pot synthesis of the Hantzsch 1,4-dihydropyridines

Alginic acid, a naturally occurring polysaccharide, in its granular form and without any post-modification was found to be an efficient, environmentally benign, easily recoverable and low-cost catalyst for the clean and rapid synthesis of 1,4-dihydropiridine derivatives (DHPs) just based on its polysaccharide architecture. The Hantzsch pseudo-four-component reaction of ethyl or methyl acetoacetate, ammonium acetate and different aldehydes is catalyzed by alginic acid efficiently under mild conditions to afford the desired products in high to quantitative yields and clean reaction profiles. Avoiding the use of any transition metal, the use of a one-pot and multi-component procedure for the synthesis of DHPs, the reusability of the catalyst and operational simplicity are important features of this methodology.