Investigations into the mechanism of the action of alkali in methanol on 3,6-dibenzyl-s-tetrazines and their 1,4-dihydro-derivatives: the role of s-tetrazines as hydride acceptors and an X-ray determination of the structure of 3,6-bis(4-chlorobenzyl)-1,4-dihydro-s-tetrazine

Abstract

Evidence is presented for the mechanism of the reaction of potassium hydroxide with 3,6-dibenzyl-s-tetrazines in which some tetrazine molecules act as hydride acceptors to become dihydro-derivatives which, in turn, react with alkali in a competing reaction to form the corresponding 1,3,4-oxadiazoles. The known action of alkali on 3,6-dibenzyl-1,4-dihydro-s-tetrazines to form 1,3,4-oxadiazoles has been shown to require the presence of an oxidising agent and tetrazine can play this role. The structures of the dihydro-derivatives of s-tetrazines have been in doubt, being called 1,2-and/or 1,4-compounds almost at random, but an X-ray determination of the structure of the dihydro-derivative of 3,6-bis(4-chlorobenzyl)-s-tetrazine has shown conclusively that it exists as the 1,4-dihydrocompound.