Synthetic strategies, characterization and antimicrobial evaluation of novel angular heteroannulated furo[3,2-g]chromenes

The starting substrate 5-chloro-4,9-dimethoxy-7-oxo-7H-furo[3,2-g]chromene-6-carbonitrile (2) was efficiently synthesized from chlorination of the corresponding hydroxy derivative. The presence of adjacent cyano and chloro functions was employed for construction a variety of five, six and seven membered rings annulated furo[3,2-g]chromenes. Treating precursor 2 with hydrazine, phenylhydrazine and hydroxylamine yielded furo[3,2:6,7]chromeno[4,3-c]pyrazoles 3, 4 and furo[3,2:6,7] chromeno[3,4-d]isoxazole 5, respectively. Also, reaction of compound 2 with a diversity of 1,3-N,N-binucleophiles such as guanidine, cyanoguanidine, thiourea, acetamidine and benzamidine produced annulated furo[3,2:6,7]chromeno[4,3-d]pyrimidines 6-10, respectively. Further, treatment of compound 2 with a variety of 1,4-binucleophiles namely ethylenediamine, o-phenylenediamine and 2-aminophenol yielded furo[3,2:6,7]chromeno[4,3-e][1,4]diazepine 11, furo[3,2:6,7]chromeno[4,3-b][1,5]benzodiazepine 12 and furo[3,2:6,7]chromeno[4,3-b][1,5]benzoxazepine 13, respectively. Some of the synthesized compounds seemed good antimicrobial activity especially compounds 3, 6 and 8. Using analytical and spectral results, the structures of the prepared compounds were established.