N-Alkylations and O-Alkylations of Nitro-Substituted 1,3-Diphenylureas: Preparations of Propellant Stabilizer Derivatives

Abstract

A procedure has been developed for the N- ethylation and methylation of 1,3-diphenylureas, ArNRCONHAr′ (R = H, Me or Et), through treatment with sodium hydride and iodoalkane in dimethylformamide. The reaction was general, provided that the aniline to be alkylated was substituted with no more than one nitro group. ArRNCONR′Ar′ derivatives prepared were: R = R′ = Et (and Me); Ar = phenyl, Ar′ = 2-nitrophenyl and 4- nitrophenyl ; Ar = 2-nitrophenyl, Ar′ = 2-nitrophenyl and 4-nitrophenyl; Ar = Ar′ = 4-nitrophenyl. Two mixed derivatives were also prepared: R = Et, R′ = Me, Ar = phenyl, Ar′ = 2-nitrophenyl and 4-nitrophenyl. O-Alkylated isourea products were obtained in the reactions of 1-(2,4- dinitrophenyl )-3-(2-nitrophenyl)urea and 1-(2,4-dinitrophenyl)-3-(4- nitrophenyl )urea. The use of potassium carbonate as the base led to apparently exclusive O- alkylation of 1,3-bis(2-nitrophenyl)urea although the reaction was not general. 1-(2,4-Dinitrophenyl)-1,3- diethyl-3-phenylurea was prepared by using silver oxide and obtained as a mixture with the isourea . Many of the compounds prepared are important nitro derivatives of the propellant stabilizers, ethyl and methyl centralite.