Reactions of 4-cyano-3 (2, H)-pyridazinone (1) and tetrazolo [1, 5-b] pyridazine-8- carbonitrile (4) with phenylmagnesium chloride were found to be governed by formal replacement of the nitrile function to afford the phenyl-substituted pyridazine derivatives 3 and 5 rather than the expected aryl heteroaryl ketones.
