A mixture of 4-bromo-2-(4-fluorobenzyl)-5-(4-methyl-3-oxopiperazin-1-yl)pyridazin-3(2H)-one (0.2 g, 0.51 mmol), dicyclohexylmethylamine (0.15 g, 0.76 mmol), and bis-(tri-t-butylphosphine)palladium (0) (52 mg, 0.10 mmol) in anhydrous methanol (5 mL) was heated in a stainless steel pressure vessel under an atmosphere of carbon monoxide (250 psi) in an oil bath at 90° C. overnight. The resultant mixture was diluted with methanol, filtered through a pad of Celite. The filtrate was concentrated under vacuum. The residual oil was triturated with methanol. The white solid precipitated was filtered to provide the titled dione.
