Water → 10-hydroxymethylene-5H,10H-imidazo[1,2-a]indeno[1,2-e]pyrazin-4-one

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Reaction Steps

A solution of 1.4 g of 10-dimethylaminomethylene-5H,10H-imidazo[1,2-a]indeno[1,2-e]pyrazin-4-one in 35 ml of 5N hydrochloric acid is stirred for 30 minutes at a temperature in the region of 25° C. After addition of 60 ml of distilled water and neutralization with 120 ml of saturated aqueous sodium hydrogen carbonate solution, the solid formed is separated out by filtration, washed twice with 60 ml in total of distilled water and air-dried. The product obtained (1.1 g) is dissolved in 120 ml of dimethyl sulphoxide and, after addition of 120 ml of distilled water, the solid formed is separated out by filtration, washed twice with 10 ml in total of distilled water and twice with 10 ml in total of acetone and then dried under reduced pressure (1 mmHg; 0.13 kPa) at 100° C. 1 g of 10-hydroxymethylene-5H,10H-imidazo[1,2-a]indeno-[1,2-e]pyrazin-4-one is thus obtained as a 60/40 mixture of the Z and E forms, decomposing without melting at 290° C. [N.M.R. spectrum: (200 MHz; DMSO d6 ; δ in ppm): a 60/40 mixture of isomers is observed: from 7.20 to 7.40 (mt, 2H: --H7 and --H8); 7.56 and 7.64-8.29 and 8.79 (4s broad, twice 1H: --H of the imidazole); from 7.80 to 8.15 (mt, 2H: --H6 and --H9); 8.21 and 8.24 (2s, 1H in total: =CH--O--); 12.43 (cplx, 1H: --NH--)].

Provenance & Evidence