Unsaturated nitrogen compounds containing fluorine. Part IV. Thermal reactions of hexafluoroacetone azine with hydrocarbon terminal olefins to give (1-pyrazolin-1-ylio)methanides or pyrazolines

Abstract

Hexafluoroacetone azine reacts with olefins of the type CH₂:CMeR (R = Me, Et, or Prⁱ) at 60–70 °C to give the stable 1,3-dipolar azomethinimines [2-(1-pyrazolin-1-ylio)propan-2-ides](CF₃)₂[graphic omitted]MeR in high yield (>90%), while with olefins of the type CH₂:CHR (R = Prⁱ or Bu^t) the corresponding 3-pyrazolines (CF₃)₂CH·[graphic omitted]R are formed in high yield (>85%). Reaction of the azomethinimine (R = Prⁱ) with isobutene at room temperature or with propene at 0°C gives the corresponding criss-cross adducts (100%), but the pyrazoline (R = Prⁱ) does not react with 3-methylbut-1-ene at 120°C. Flow pyrolysis of the azomethinimines (R = Me or Et) at 400°C gives quantitative yields of the azine and the corresponding olefin, while flow pyrolysis of the pyrazoline (R = Prⁱ) at 450 °C affords 1,1,1,3,3,3-hexafluoro-2-trifluoromethylpropane (100%) and the pyrazole Me₂CH·[graphic omitted]H (100%).