To an ice cooled suspension of 5.29 g (0.02 mol) 1-(4-chlorophenyl)-1,4-dihydro-4-oxo-6-methyl pyridazine-3-carboxylic Acid (see Example 12) and 2.02 g (0.02 mol) of triethylamine in 75 ml of toluene there is added 3.25 g (0.02 mol) of cyclohexyl chloroformate. The suspension formed is stirred at room temperature for 15 minutes and to it there is added 3.2 g (0.022 mol) of cyclohexanol in 50 ml of toluene. The mixture is stirred at room temperature for 38 hrs. and to it there is added 100 ml of water. The mixture is stirred at room temperature for 1 hr. and the toluene layer is isolated and poured into 600 ml of hexane. The suspension formed is stirred at room temperature for 1/2 hr. and is vacuum filtered. The filter cake is air dried to afford 4.5 g (65% yield) of product, mp 160°-162° C.
