Hexamethyldisilazane → 4-(Cyclopentylamino)-1-methylimidazo(1,2-a)quinoxaline

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A mixture of 3.5 g of 1-methylimidazo[1,2-a] quinoxalin-4(5H)-one (example 2), 13 ml of hexamethyl disilazane, 0.5 g of ammonium sulphate and 8.7 ml dicyclopentylamine is stirred at 120° C. in a Dean-Stark apparatus for 24 h. After concentrating the resulting mixture under vacuum, the residue is added with water and extracted with ethyl acetate. The organic extracts are then washed with water and saturated NaCl, dried and evaporated, thereby obtaining 1.5 g of a raw product that is subsequently chromatographed on SiO2 (eluent: CH2Cl2 /AcOEt 97:3). By recrystallizing from ethyl acetate, there is obtained 4-cyclopentylamino-1-methyl imidazo [1,2-a]quinoxaline. m.p. (DSC)=167.3° C. (onset); IR (KBr): 3294, 2948, 1544 cm-1 ; 1H-NMR (CDCl3): δ8.0 (1H,dd), 7.4÷7.05 (3H,m), 6.0 (1H,d), 4.6 (1H,m), 2.8 (3H,s), 2.3÷2.05 (4H,m), 2.0÷1.4 (4H,m); UV (EtOH): λmax =225, 243, 272 301, 316, 329 nm. Elementary analysis for C16H16N4 (m.w. 266.35): calcd. C 72.15, H 6.81, N 21.03%; found C 71.86, H 6.81, N 20.79%.

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