Synthetic procedures yielding targeted nitro and nitroso derivatives of the propellant stabilisers diphenylamine, N-methyl-4-nitroaniline, and N,N′-diethyl-N,N′-diphenylurea

Synthetic methodologies have been developed which yield a variety of diphenylamine (DPA) and 1,3-diethyl-1,3-diphenylurea (ethylcentralite or EC) propellant stabiliser degradation derivatives in high yield. The N-alkyl nitroanilines (N-methyl-2,4,6-trinitroaniline; N-methyl-2,4-dinitroaniline; N-ethyl-2,4,6-trinitroaniline; N-ethyl-2,4-dinitroaniline; N-ethyl-4-nitroaniline; N-ethyl-2-nitroaniline) have been obtained either by reaction of the parent aniline with the required alkyl halide under mild conditions or via Ullmann type chemistry. A robust and high yielding approach for the synthesis of di, hi and tetranitrodiphenylamines (2,2',4,4'-tetranitrodiphenylamine; 2,4,4'-trinitrodiphenylamine; 2,2',4-trinitrodiphenylamine; 2,4,6-trinihodiphenylamine; 2,4-dinitrodiphenylamine) is reported which involves passing the nitroanilines and chloronitrobenzenes down a base activated alumina column. The N-nitroso-N-alkyl compounds (N-nitroso-N-ethyl-4-nitroaniline; N-nitroso-N-ethyl-2-nitroaniline; N-nitroso-N-Methyl-4-nitroaniline; N-ethyl-N-nitrosoaniline; N-nitroso-2-nitrodiphenylamine) have been synthesised using nitrosyl acetate in acetic acid as the N-nitrosating agent.