Unsaturated nitrogen compounds containing fluorine. Part 9 [1]. The preparation of 2,5-dichloro-l,l,l,6,6,6-hexafluoro-3,4-diazahexa-2,4-diene and its reaction with amines

Abstract

2,5-Dichloro-1,1,1,6,6,6-hexafluoro-3,4-diazahexa-2,4-diene ( 1) has been prepared in goodyield (60%) by the reaction of 1,2-bis(trifluoroacetyl)hydrazine with a mixture of N,N-dimethylaniline hydrochloride and phosphoryl chloride. Nucleophilic displacement ofchlorine from azine 1 occurs readily on reaction with primary amines RNH 2 (RPr i, Bu s,Ph, 4-FC 6H 4, 2,6-Cl 2C 5H 2NCH 2-4) and with secondary amines (morpholine and Et 2NH);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 CF 3(NRR′)NNCClCF 3 ( 7) (RH, R′Pr i;RR′Et) and CF 3C(NRR′)NNC(NRR′)CF 3 ( 8) (RH, R′=Pr i, Bu s and 2,6-Cl 2pyCH 2-4; RR′: Et; RR′CH 2CH 2OCH 2CH 2) and the imidoyl tautomersPhNC(CF 3)NHNCClCF 3 ( 9a) and ArNC(CF 3)NHNHC(CF 3)NAr ( 110) (ArPh and4-FC 6H 4). On heating at temperatures up to 120 °C, the compounds 10a (ArPh), 10b(Ar4-FC 6H 4) and 9a undergo cyclisation (with elimination of ArNH 2 or HCl) to affordthe corresponding 4-aryl-4 H-1,2,4-triazoles ( 22); the azine 8a (R=Pr i) does not cycliseunder these conditions. The azine 7a (RH, R′Pr i) on hydrolysis (NaOH/EtOH thenH 3O +) gives the trifluoroacetylhydrazine Pr iNC(CF 3)NHNHCOCF 3 ( 20) in excellent yield(92%).