![]() | Only 14 pages are availabe for public view |
Abstract As one of the main goals of present thesis, quinazoline synthesis permits an easy synthetic entry to a class of 1, 2, 4-triazoles based substituted quinazoline and 1, 2, 3-triazole-N-glycoides based quinazoline structure. The 1, 3-dipolar cycloaddition strategy was employed to create the 1, 2, 3-triazole core structure through click-reaction in the targeted molecules. N-substituted quinazolinethione compounds (2-4) were synthesized by reaction with aseries of isothiocyanate derivatives and 2-aminobenzoic acid (1) in ethanol was refluxed in the presence of triethylamine for 5 h. N-substituted quinazolinethione derivatives (2-4) with hydrazine hydrate afforded the corresponding derived 2-hydrazinyl products(5-7) The formed hydrazinyl quinazoline derivatives were then allowed to react with carbon disulfide in basic medium and the 4-substituted-1-mercapto- [1,2,4]triazolo[4,3-a] quinazolin-5(4H)-one derivatives (8,9)resulted in good yields. The sulfanyl-substituted ester derivatives (10, 11) formed by esterification of the starting quinazoline thoil (2,3) in dry DMF with ethyl chloroacetate in the presence of and anhydrous potassium carbonate Following a 24-hour stirring period at 70 °C. compounds (12,13) were converted to the corresponding 4-substituted-1-hydrazinyl-[1,2,4] triazolo[4,3-a]quinazolin-5(4H)-one (12,13) via reaction with thiosemicarbzide in absolute methanol ,mixed with 20 ml of sodium methoxide and then acidified with HCl. The sulfanyl-aceto hydrazide (14, 15) was prepared from the compounds (10, 11) according to the reaction with hydrazine hydrate (80%) in absolute ethanol after stirring the mixture for 24hr at room temperature The sulfanyl-aceto hydrazide (14, 15) was found a useful key structure for the synthesis of functionalized bicyclic compounds. Thus, reacting ethyl cyanoacetate and malononitrile with the acetyl hydrazides (12, 13) in presence of para-chlorobenzaldehyde in absolute ethanol afforded the bicyclic structural products of the quinazolyl-triazolopyridine hybrid products incorporating aryl substituents The terminal acetylenic derivative (22, 23) of the quinazolyl thio acetic acid (20, 21) derivative was synthesized via thioalkylation of the starting quinazoline-thiol (2, 3) by reaction with chloroacetic acid in dryDMFand the prescnce of anhydrous potassium carbonate with continuous stirring was for 36 h at 100 °C t followed by esterification reaction with propargyl alcohol in 30 ml of absolute ethanol and 1ml of sulfuric acid at 80°C for 36 hours while stirring constantly The crucial acetylenic terminal active center compounds (24, 25) were produced through the interaction of quinazoline-thiols (2, 4) were dissolved in (H2O + EtOH; (1 :2 ) (20ml) in an alkaline environment anhydrous potassium hydroxide) with stirring for about 20 minutes in an ice bath. Propargyl bromide was added dropwise and stirring was continued for 7h. |