Heterocyclic polyfluoro-compounds. Part XXIII. Reaction of some 2-, 3-, and 4-substituted pyridine 1-oxides, 5-methylpyrimidine 1-oxide, and quinoline 1-oxide with perfluoropropene, and of pyridine 1-oxide with perfluoro-(2-methylpent-2-ene): synthesis of 2-(1,2,2,2-tetrafluoroethyl)-pyridines or -pyrimidines and their N-oxides and of 2,2,3-trifluoro-2,3-dihydro-3-trifluoromethylfuro[3,2-b]pyridine

Abstract

Perfluoropropene reacts thermally with 2-chloro-, 2-cyano-, and 2-(1,2,2,2-tetrafluoroethyl)-pyridine 1-oxide and with 4-methyl-, 4-methoxy-, and 4-nitro-pyridine 1-oxide to yield carbonyl fluoride and the corresponding 2- or 4-substituted 6-(1,2,2,2-tetrafluoroethyl)pyridines. Thermal deoxygenation of 3-bromo-, 3-chloro-, or 3-fluoro-pyridine 1-oxide with perfluoropropene yields a mixture of the corresponding 3- and 5-halogeno-2-(1,2,2,2-tetrafluoroethyl)pyridines plus 2,2,3-trifluoro-2,3-dihydro-3-trifluoromethylfuro[3,2-b]pyridine and, in the cases of 3-bromo- and 3-chloro-pyridine 1-oxide, 3- and 5-fluoro-2-(1,2,2,2-tetrafluoroethyl)pyridine. Oxidation of the 2-(1,2,2,2-tetrafluoroethyl)pyridines 2-(CF₃·CHF)C₅H₃NX (X = H, 3-Br, 3-Cl, 3-F, 4-Me, 4-NO₂, 5-Br, 6-Cl, 6-CN, or 6-Me) with peroxy-acid yields the corresponding 1-oxides; 2,2,3-trifluoro-2,3-dihydro-3-trifluoromethylfuro[3,2-b]pyridine 4-oxide can be prepared similarly. Deoxygenation of pyridine 1-oxide with perfluoro-(2-methylpent-2-ene) yields 2-(2H-hexafluoroisopropyl)pyridine.

Reaction of 5-methylpyrimidine 1-oxide with perfluoropropene yields 5-methyl-4- and 5-methyl-2-(1,2,2,2-tetrafluoroethyl)pyrimidine; oxidation of the former with peroxy-acid gives predominantly 5-methyl-4-(1,2,2,2-tetrafluoroethyl)pyrimidine 1-oxide.