Chemoselective reaction of benz(<i>g</i>)indole based bisheterocycle dicarboxylate towards hydrazine hydrate: Synthesis and antimicrobial activity of new triheterocycles-5-pyrrolylaminocarbonyl/ mercaptooxadiazolyl/4-allyl-5-mercaptotriazolylmethoxy-1-furfuryl-2-methylbenz(<i>g</i>)indoles

Abstract

Chemoselectivity of C₅-ester over that of C₃-ester function of the benz(<i>g</i>)indole based bisheterocycle dicarboxylate towards the nucleophilic attack of hydrazine hydrate has been evidenced by the exclusive formation of 1-furfuryl-3-ethoxycarbonyl-5-hydroxy-2-methylbenz(<i>g</i>)indole-5-yloxyacetic acid hydrazide <b style="">5</b> which is reacted separately with acetonyl acetone, carbon disulphide in boiling ethanolic potassium hydroxide and allyl isothiocyanate to produce respectively 1-furfuryl-3-ethoxycarbonyl-5-(2,5-dimethylpyrrol-1-yl)aminocarbonylmethoxy-2-methylbenz(<i>g</i>)indole <b style="">7</b>,<b style=""> </b>1-furfuryl-3-ethoxy-carbonyl-5-(5-mercapto-1,3,4-oxadiazol-2-yl)methoxy-2-methylbenz(<i>g</i>) indole <b style="">8</b>, and 1-furfuryl-3-ethoxycarbonyl-5-(N-allylthiosemicarbazinocarbonyl)methoxy-2-methylbenz(<i>g</i>)indole <b style="">9</b>. The thiosemicarbazide <b>9</b> when heated with 4% NaOH undergoes cyclisation with concomitant hydrolysis of C₃-ester group to yield 1-fufuryl-5-(4-allyl-5-mercapto-1,2,4-triazol-3-yl)methoxy-2-methylbenz(<i>g</i>)indole-3-carboxylic acid <b style="">10</b>. The structures of newly synthesized compounds are confirmed on the basis of their spectral and analytical data and the compounds are also screened for their antibacterial and antifungal activities.