1,3-Dipolar character of six-membered aromatic rings. Part X. Pyridazine and benzopyridazine betaines

Abstract

The betaines 3-methyl-1-oxidophthalazinium and 6-chloro-2-methyl-4-oxidocinnolinium react as 1,3-dipoles across the 2- and 4-positions with acetylenic dipolarophiles. Phthalazin-1(2H)-one and 6-chloro-4-cinnolone also possess 1,3-dipolar reactivity and react with benzyne. The preparations of 1-methyl-3-oxidopyridazinium and 1,6-dimethyl-3-oxidopyridazinium are described, and the tautomerism of the betaine monoprotonated cations is discussed.