Convenient Synthesis of Dihydropyridine and Dihydropyrimidinethione Derivatives Using a Porphyrin Cored G1 PAMAM Dendrimer as a Homogeneous Catalyst

Porphyrin cored poly(amidoamine) (G1 POR-PAMAM) dendrimer based simple, mild, and selective homogeneous base catalyst was successfully synthesized. It was characterized by different spectral studies including UV-Vis, FT-IR, H-1 NMR and C-13 NMR. The G1 POR-PAMAM was a very selective and efficient organocatalyst capable of promoting chemical reactions in an environment friendly way with high efficiency. The product selective property of G1 POR-PAMAM was mainly studied in Biginelli andHantzschpyridine synthesis reactions. The G1 POR-PAMAM catalyst was acting as a chemical switch for the selective synthesis of pyridine and pyrimidine derivatives exclusively. It was a convenient, green and efficient procedure for the exclusive synthesis of 1,4-dihydropyridine, or 3,4- dihydropyrimidin-2(1H)-thione derivatives using the three-component coupling reaction of aldehydes, ethylacetoacetate and ammonium thiocyanate. A variety of these compounds were produced in single step by the use of different starting materials. Within 45 minutes, the products were obtained with high yield (92-99%). The catalyst could be reused upto six reaction cycles without significant loss of its catalytic activity.