UNSATURATED NITROGEN-COMPOUNDS CONTAINING FLUORINE .9. THE PREPARATION OF 2,5-DICHLORO-1,1,1,6,6,6-HEXAFLUORO-3,4-DIAZAHEXA-2,4-DIENE AND ITS REACTION WITH AMINES

2,5-Dichloro-1,1,1,6,6,6-hexafluoro-3,4-diazahexa-2,4-diene (1) has been prepared in good yield (60%) by the reaction of 1,2-bis(trifluoroacetyl)hydrazine with a mixture of N,N-dimethylaniline hydrochloride and phosphoryl chloride. Nucleophilic displacement of chlorine from azine 1 occurs readily on reaction with primary amines RNH2 (R = Pr(i), Bu(s), Ph, 4-FC5H4, 2,6-Cl2C5H2NCH2-4) and with secondary amines (morpholine and Et2NH); in general, mono- or di-substitution can be achieved by varying the azine/amine ratio (1:2 or 1:4). The products are the azines CF3(NRR')=NN=CClCF3 (7) (R=H, R'=Pr(i); R=R'=Et) and CF3C(NRR')=NN=C(NRR')CF3 (8) (R=H, R'=Pr(i), Bu(s) and 2,6-Cl2pyCH2-4; R-R = Et; R-R' = CH2CH2OCH2CH2) and the imidoyl tautomers PhN=C(CF3)NHN=CClCF3 (9a) and ArN=C(CF3)NHNHC(CF3)=NAr (10) (Ar=Ph and 4-FC6H4). On beating at temperatures up to 120-degrees-C, the compounds 10a (Ar=Ph), 10b (Ar=4-FC6H4) and 9a undergo cyclisation (with elimination of ArNH2 or HCl) to afford the corresponding 4-aryl-4H-1,2,4-triazoles (22); the azine Sa (R=Pr(i)) does not cyclise under these conditions. The azine 7a (R=H, R'=Pr(i)) on hydrolysis (NaOH/EtOH then H3O+) gives the trifluoroacetylhydrazine Pr(i)N=C(CF3)NHNHCOCF3 (20) in excellent yield (92%).