Unsaturated nitrogen compounds containing fluorine. Part 18. Novel cycloaddition products from the reaction of quadricyclane with fluorinated azines and the azomethine imide 2-hexafluoroisopropylidene-3-methyl-3-phenyl-5,5-bis(trifluoromethyl)tetrahydropyrazol-2-ium-1-ide

Abstract

Reaction of quadricyclane (6) with the azine CF 3CCl = NN = CClCF 3 (1a) in dichloromethane at 70 °C afforded the expected exo-[2 + 2 + 2] cycloadduct 8a (70%), and the unexpected exo-1,3-dipolar cycloadduct 3a, formed by a non-concerted pathway and isolated as the hydrolysed compound, amide 4a (19%). The corresponding reaction of 6 with hexafluoroacetone azine (CF 3) 2C=NN=C(CF 3) 2 (1b) at 70 °C yielded the exo-[2 + 2 + 2] cycloadduct 8b (54%), the bis-[2 + 2 + 2] 2:1 cycloadduct 9b (8%), formed by further reaction of 8b with 6, and the exo,exo-2:2 cycloadduct 10 (31%), which arose via concerted 1,3-dipolar cycloaddition of azine 1b to the olefinic double bond of 1:1 adduct 8b to give the 1:2 adduct, azomethine imide 14, followed by non-concerted 1,3-dipolar cycloaddition of 14 to quadricyclane 6. In contrast, the corresponding reaction of 6 with the azines CF 3CCl = NN = CFCF 3 (1c) (at 55 °C) and CF 3CF = NN = CFCF 3 (1d) (at 50 °C) gave only the exo-[2 + 2 + 2] 1:1 cycloadducts, i.e. the compounds 8c (65%) (formed by reaction involving the CF 3CF=N grouping in 1c) and 8d (20%) (formed by reaction involving the CF 3CCl = N grouping in 1c) and the compound 8e (88%), as a mixture of two isomers in the ratio 72:16, respectively. Treatment of 6 with the azomethine imide ( CF 3 ) 2 C = N + − N − C ( CF 3 ) 2 CH 2 ⎴ CMePh ( 7) at 70 °C in dichloromethane afforded the exo-1,3-dipolar 1:1 cycloadduct 11 as two stereoisomers [ 11a (12%) and 11b (17%)], the 1-pyrazoline ( CF 3 ) 2 C − N = N − CMePh − ⎴ CH 2 ( 12) (26%) and the symmetrical 1:2 cycloadduct 13b (32%) formed by further reaction of 11b with azomethine imide 7. Reaction of 6 with the azine CF 3(NH 2) = NN = C(NH 2)CF 3 ( 1e) at 100 °C was unsuccessful, as was reaction with 1:1 cycloadduct 8a at 100 °C.