Synthesis, reactions, antitumor and antimicrobial activity of new 5,6-dihydropyrrolo[2,1-a]isoquinoline chalcones.

Stirring of 2-(6,7-dimethoxy-3,4-dihydroisoquinolin-1-yl)acetonitrile 1 with thiophene-2-carbaldehyde 2 in absolute ethanol in the presence of hydrochloric acid yielded 2-(6,7-dimethoxy-3,4-dihydroisoquinolin-1-yl)-3-(thiophen-2-yl)acrylonitrile hydrochloride 3. Refluxing of arylidene 3 with α-ketohydrazonoyl halides 4-7 in the presence of triethylamine in chloroform afforded dihydropyrrolo[2,1-a]isoquinolines 11-14. Claisen-Schmidt condensation of 11 with aryl aldehydes 15a-f or pyrazole aldehydes 17a-d in ethanol in the presence of sodium hydroxide solution produced chalcones 16a-f and 18a-d. Refluxing of chalcone 16f with hydrazine hydrate in ethanol afforded pyrazoline 19 which gave N-phenylcarbothioamide derivative 20 on stirring with phenyl isothiocyanate in dry ether. Also, refluxing of 19 with acetic anhydride or formic acid afforded acetyl-pyrazoline derivative 21 or formyl-pyrazoline derivative 22, respectively. Antitumor activity for some new synthesized compounds showed that compounds 16b and 16d had anticancer activities. Antimicrobial activities for the newly synthesized compounds revealed the most potent compounds 16c, 18b and 18d against E. coli, compounds 16b, 18b and 18d against B. mycoides, and compounds 16b, 16c and 18b against C. albicans. Moreover, compound 18b had the lowest MIC values against E. coli and B. mycoides, with MIC values of 40 and 60 µg/ml, respectively.