Phosgene → 4,5-dihydro-5-methyl-6-[p-(1-methylprop-2-ynyloxycarbonylamino)-phenyl]-3(2H)-pyridazinone

Participants

Reaction Conditions

Reaction Steps

3.5 g (49.9 millimoles) of 1-methylprop-2-ynol are added dropwise to a stirred solution of 9.9 g (100 millimoles) of phosgene in 100 ml of absolute ether at -10° C. The reaction solution is then stirred for 1 hour at -10° C. followed by one hour at room temperature, and the excess phosgene is removed by means of a dry stream of nitrogen, after which the ether is removed under reduced pressure at room temperature. The 1-methylprop-2-ynyl chloroformate which is left (5.9 g) is reacted with 5.0 g (24.6 millimoles) of 6-(p-aminophenyl)-4,5-dihydro-5-methyl-3(2H)-pyridazinone by the method described in Example 31. The reaction mixture is also worked up as described in Example 31. After recrystallizing the product first from ethanol/water, then from ethyl acetate/petroleum ether and finally from dimethylformamide/water, 1.7 g (23% of theory) of 4,5-dihydro-5-methyl-6-[p-(1-methylprop-2-ynyloxycarbonylamino)-phenyl]-3( 2H)-pyridazinone are obtained as colorless crystals of melting point 206°-207° C.

Provenance & Evidence