Unsaturated nitrogen compounds containing fluorine. Part 16. The synthesis of 3,5-bis(trifluoromethyl)-1 H-1,2,4-triazole and some 4-substituted derivatives from 2,5-dichloro-1,1,1,6,6,6-hexafluoro-3,4-diazahexa-2,4-diene

Abstract

The dichloroazine 5 has been converted into the monoaminoazines CF 3C(NHR)=NN=CClCF 3 (6) [a, R = Ph (89%); b, R = H (81%); c, R = Me (89%); d, R = CH 2CO 2Me (96%); e, R = CH 2CO 2Et (95%)] and the diaminoazines CF 3C(NHR) = NN = C(NHR)CF 3 (4) [c, R = H (96%); d, R = Me (94%); e, R = CH 2CO 2Me (50%); f, R = CH 2CO 2Et (77%)] by reaction with ammonia or the appropriate primary amino compound; with hydroxylamine the syn-oxime CF 3CCl = NNHC(CF 3) = NOH (8) (86%) was formed. The mixed diaminoazines CF 3C(NHR) = NN = C(NHR′)CF 3 (4) [g, R = H, R′ = Ph; h, R′ = Me, R′ = H; i, R = Me, R′ = CH 2CO 2Me; j, R = CH 2CO 2Me, R′ = Ph (92%–96%)] have been synthesised from the monoaminoazines 6a-d. A solution of the diaminoazine 4c, heated in ethanol under reflux, gave 3,5-bis(trifluoromethyl)-1 H,2,4-triazole (1a) (28%) and its ammonium salt NH 4 +[C 2N 3(CF 3) 2] − (7b) (54%), while the azines 4g and 4j under the same conditions each afforded 4-phenyl-3,5-bis(trifluoromethyl)-4 H-1,2,4-triazole (2c) (ca. 85%). Thermolysis of the diaminoazines 4c-f and 4h in vacuo over the range 120–150 °C gave the following results: 4c → 7b (98%); 4d → MeNH 3 + [C 2N 3(CF 3) 2] − (7c) (ca. 26%)+Me 4N + [C 2N 3(CF 3) 2] − (7d) (ca. 13%) + 4-methyl-3,5-bis(trifluoromethyl)-4 H-1,2,4-triazole (2b) (54%) + 1-methyl-3,5-bis(trifluoromethyl)-1 H-1,2,4-triazole (1b) (1.5%); 4e → the 4-carbomethoxymethyltriazole (2e) (93%); 4f → the 4-carboethoxymethyltriazole (2f) (82%); 4h → 1a (11%) + 2b (54%) + 7c (31%). Treatment of salt 7b with aqueous hydrochloric acid afforded the triazole 1a (75%).