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A new and efficient conjugate addition of trimethyl and triethyl phosphites to 3-x-azidoacetylcoumarin (1) has been studied. The reaction proceeded smoothly at r.t. furnishing 1,2,3,4-triazaphosphole coumarin derivatives 4a,b in $75% yields. Linear substituted triazoles 10a,b were also obtained from the reactions of 1 with a-keto ylides, acetyl-and benzoylmethylene triphenylphosphoranes. Contrary to these results, Wittig reaction was occurred when 1 was allowed to react with a-alkoxycarbonylmethylene-and cyanomethylenetriphenylphosphoranes 7c-e as well as with methylidene-and benzylidenetriphenylphosphoranes 8a,b resulting in the formation of the corresponding olefins either as an intermediate 14b or as final products 11a-c.
Treatment of 5,6-di(2-furyl)-3-thioxo-2,3-dihydropyridazine-4-carbonitrile with phosphonate carboanions stabilised with electron withdrawing group (CO 2 R, 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.
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