Antimicrobial activity of novel fused nitrogen, sulfur and phosphorus containing-heterocycles and relevant phosphonates with difurylpyridazine species

Treatment of 5,6-di(2-furyl)-3-thioxo-2,3-dihydropyridazine-4-carbonitrile with phosphonate carboanions stabilised with electron withdrawing group (CO2R, CN, SR?) led, under microwave irradiation and the effect of basic catalysis, to excellent yields of a variety of condensed sulfur, nitrogen and phosphorus-containing heterocycles as major products, along with fused thieno- and thiazole ring systems bearing a phosphonate moiety. On the other hand, fused thiazaphosphinine oxide and thiopyranone phosphonate were obtained in equal yields from the reaction of 5,6-di(2-furyl)-3-thioxo-2,3-dihydropyridazine-4-carbonitrile with diethyl vinylphosphonate. Screening results of antimicrobial potency for the products were discussed in terms of structure-activity relationships (SAR), and an attempt was made to define the structural features for lead compounds.