An advanced green fused diazonium initiating substance

Abstract

In recent decades, a series of representative synthetic methods for fused energetic materials have been reported, but most of them are still subject to some limitations. In this work, a novel unexpected one-step method for constructing fused tricyclic compounds like 5-amino-6-azido-[3′,4′:5,6]pyrido[4,3-d][1,2,3]triazine[1,2,5]oxadiazolo-8-oxide (OPTA) and (E)-N-(6-amino-[1,2,5]oxadiazolo[3,4-b]pyrazolo[5,4-d]pyridin-5(4H)-ylidene)nitramide (OPPD) from amino cyanide intermediates has been achieved under the conventional TFA/TFAA/100% HNO₃ nitration reaction system. This one-step process that involves at least four steps of reaction is rarely reported in the synthesis of energetic materials. It is worth noting that OPPD is the first example of a fused diazonium primary explosive with higher decomposition temperature (T_d = 181 °C), relatively lower sensitivities (FS = 40 N, IS = 5 J) and greater initiating power (MPC = 30 mg) than the most commonly used organic primary explosive DDNP (T_d = 157 °C, FS = 24.7 N, IS = 1 J, MPC = 70 mg). This work is a giant step forward to advanced green primary explosives and would improve future prospects for the design of fused energetic materials.