REGIOSELECTIVE OXYFUNCTIONALIZATION OF UNACTIVATED TERTIARY AND SECONDARY C-H BONDS OF ALKYLAMINES BY METHYL(TRIFLUOROMETHYL)DIOXIRANE IN ACID-MEDIUM

Tetrafluoroborate salts of primary, secondary, and tertiary alkylamine s are resistant toward N oxidation by methyl(trifluoromethyl)dioxirane (1b), which allows the selective oxidation of aliphatic tertiary and secondary C-H bonds in the alkyl side chain. The oxidations are carrie d out at 0-degrees-C with a ketone-free solution of methyl(trifluorome thyl)-dioxirane (1b) in methylene chloride. By this procedure, within 3 h the tertiary C-H bonds of acyclic, cyclic, and polycyclic amines 2 a-e are hydroxylated to give the corresponding amino alcohols 3a-e. In the case of the acyclic amines 2a,b longer reaction times were necess ary, and in the strong acid medium the corresponding amino acetamides 4a,b were obtained through Ritter reaction with the solvent acetonitri le. The strong electron-withdrawing nature of the ammonium group deact ivates the oxidation of even tertiary C-H bonds at the alpha and beta positions. Secondary C-H bonds of the linear aliphatic primary amines 2f-h were oxidized exclusively at the epsilon position to give the 2,3 ,4,5-tetrahydro-6-alkylpyridines 6f-h after intramolecular condensatio n of the corresponding amino ketones 5f-h.