N-fluoro-compounds. Part IV. Photochemical and fluoride-initiated reactions between perfluoro-N-fluoropiperidine and perfluoropropene

Abstract

Photolysis of perfluoro-N-fluoropiperidine in the presence of perfluoropropene gives perfluoro-(2-methylpentane), perfluoro-(2,3-dimethylbutane), perfluoro-(N-propylpiperidine). perfluoro-(N-isopropylpiperidine), perfluoro-[N-(1,3-dimethylbutyl)piperidine], a 2:2 adduct (2C₅F₁₀NF:2C₃F₆), and perfluoro-NN′-bipiperidyl. Thermal reaction of perfluoro-N-fluoropiperidine with perfluoropropene in stainless steel in the presence of caesium fluoride yields, inter alia, perfluoro-(2-isopropyl-3,4,5,6-tetrahydropyridine) and perfluoro-(2-isopropylpyridine); this conversion is believed to involve defluorination of the piperidine to perfluoro-2,3,4,5-tetrahydropyridine followed by attack on this product by perfluoroisopropyl anion and subsequent aromatisation of perfluoro-(2-isopropyl-3,4,5,6-tetrahydropyridine) thus formed. Perfluoro-(2-isopropylpyridine) can be prepared from perfluoro-N-fluoropiperidine in three separate stages according to this scheme, which exemplifies a possible useful route to 2-substituted tetrafluoropyridines.