Phosgene → 6-[p-(m-chlorobenzyloxycarbonylamino)-phenyl]-4,5-dihydro-5-methyl-3(2H)-pyridazinone

Participants

Reaction Conditions

Reaction Steps

A solution of 7.1 g (49.8 millimoles) of m-chlorobenzyl alcohol in 50 ml of absolute ether is added dropwise to a stirred solution of 11.2 g (113 millimoles) of phosgene in 100 ml of absolute ether at -20° C. The reaction solution is then stirred for 1 hour at -10° C. and for a further hour at room temperature, and thereafter the excess phosgene is removed by means of a dry stream of nitrogen and the other is then removed under reduced pressure at room temperature. The m-chlorobenzyl chloroformate which remains (12.0 g) is dissolved in 50 ml of absolute tetrahydrofuran and the solution is added, at room temperature, to a solution, prepared by the method described in Example 31, of 5.0 g (24.6 millimoles) of 6-(p-aminophenyl)-4,5-dihydro-5-methyl-3(2H)-pyridazinone in 100 ml of absolute tetrahydrofuran. The reaction mixture is then refluxed for 14 hours and is worked up by the method described in Example 31. After recrystallizing the product first from chloroform/petroleum ether, then from acetone/water and finally from propanol/water, 4.0 g (44% of theory) of 6-[p-(m-chlorobenzyloxycarbonylamino)-phenyl]-4,5-dihydro-5-methyl-3(2H)-pyridazinone are obtained as colorless crystals of melting point 165°-166° C.

Provenance & Evidence