Research on the chemistry of pyrazolidine

Sodium alkoxides readily add to the exocyclic double bond of variously substituted 4-benzylidene derivatives of 1,2-diphenyl-3,5-dioxopyrazolidine to give the sodium salts of 4-(1-alkoxybenzyl)-1, 2-diphenyl-3,5-dioxopyrazolidines, the methylation of which leads to 4-methyl-4-(1-alkoxy-benzyl)-1, 2-diphenyl-3,5-dioxopyrazolidines. This confirms the previously expressed assumption that the reason for the stability of the N-N bond and the exocyclic double bond of 4-benzylidene-1,2-diphenyl-3,5-dioxopyrazolidine in alkaline media with respect to catalytic hydrogenolysis is the formation under these conditions of a stable enolate.