Dimethylformamide → 5-methyl-6-(2-thiophen-2-yl-benzoxazol-6-yl)-4,5-dihydro-2H-pyridazin-3-one

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Reaction Steps

2.6 g (0.02 mol) thiophene-2-carboxylic acid, 3.3 g (0.02 mol) 1,1′carbonyldiimidazole and 50 ml DMF are combined and the mixture is stirred for 30 min at RT, then 4.4 g (0.02 mol) 6-(4-amino-3-hydroxy-phenyl)-5-methyl-4,5-dihydro-2H-pyridazin-3-one are added and the mixture is stirred for 4 h at 60° C. The reaction mixture is diluted with water and acidified with glacial acetic acid, the precipitated solid is filtered off, washed with water and isopropanol and then dried. The solid obtained is heated to 130° C. with 60 g polyphosphoric acid for 30 min, then poured onto ice water and then extracted with chloroform. The org. phase is washed with water, dried on magnesium sulphate and the solv. is eliminated by rotary evaporation i.V. The residue is stirred with acetone/diethyl ether, filtered off and then recrystallised from isopropanol/dioxane.

Provenance & Evidence