Synthesis of some biologically active 2&2,2-disubstituted 1,2,3,4-tetrahydro-4-thiobenzofuro [3,2-d] pyrimidines and their reactions

Abstract

The condensation of 3-amino-2-carboxamide (1) with various aldehydes in presence of hydrochloric acid gave the corresponding 2-aryl-1,2,3,4-tetrahydro-4-oxobenzofuro [3,2d] pyrimidines (2a-d). Compound 1 was converted into the required intermediate thiocarboxamide 3, by the reaction with phosphorus pentasulphide in anhyd pyridine. The acid catalyzed condensation of 3 with various ketones afforded the anticipated 2,2dialkyl-1,2,3,4-tetrahydro-4-thiobenzofuro [3,2-d] pyrimidines (4a-d) and with various aromatic aldehydes under similar conditions furnished the respective 2-aryl-1,2,3,4tetra hydro-4-thiobenzofuro [3,2-d] pyrimidines (5a-d) in good yields. The methylation of 4a-d and 5a-d led to the formation of a product which was found to be identical with 3aminobenzofuran-2-carbonitrile (6), which has already been prepared in this laboratory. Compounds 4a-d & 5c underwent displacement by amines to produce the respective derivatives 7a-i. The synthesis of 1,2,3,4-tetrahydro-2-oxo-4-thiobenzofuro [3,2-d] pyrimidine (8) from compound 3 and displacement of mercapto group of 8 to produce the corresponding substituted compounds 9a, 9b was also investigated. The structures of all the compounds were well supported by spectral and analytical data. Some of the compounds had shown moderate to appreciable antibacterial activity against S. aureus and E. coli.