Pyridazine-4,5-dicarboxylic anhydride: versatile synthon for the preparation of 1,3,7,8-tetra-azaspiro[4.5]decane derivatives with nitrogen 1,3-binucleophiles

Abstract

The title compound (1) reacted smoothly with 1,2,3-triphenyl- and 1,3-diphenyl-guanidine, with N,N′-diphenyl- and N-phenyl-thiourea, and with benzamidine to give in very good yields the 1,3,7,8-tetra-azaspiro[4.5]decane derivatives (2), (4), (6), (9), and (11), respectively, through a Smiles-type rearrangement. The reaction of compound (1) with 1,3-diphenylguanidine showed a different regiospecificity from that observed for the spiro-cyclization of dimethyl pyridazine-4,5-dicarboxylate (15) into methyl 4-oxo-1-phenyl-2-phenylimino-1,3,7,8-tetra-azaspiro[4.5]deca-6,9-diene-10-car-boxylate (19), carried out with the same reagent in the presence of sodium hydride. The structures of the new heterospiro compounds were determined on the basis of chemical and spectroscopic evidence.