Reactions of perfluorocycloimines with (polyfluoroalkoxy)trimethylsilanes and polyfluoroalkyltrifluoromethanesulfonates

The reactions of F-(5,6-dihydro-2H-1,4-oxazine) and F-(3,4-dihydro-2H-pyrrole) were investigated using two series of reagents: one is the polyfluoroalkylating agent RfOSO2CF3 and the other is the (polyfluoroalkoxy)trimethylsilane RfOSi(CH3)3. Systematic study with polyfluoroalkyl groups such as CF3CH2, C2F5CH2, CHF2CH2, and (CF3)2CH revealed that the regio-chemistry, isomer distribution, product distribution between mono-, di-, and tri-substituted products and even the reaction pathways were subtly changed by the structure of these fluoro substituents as well as by the reagent stoichiometry. A notable substitution effect was found in the reaction of F-(5,6-dihydro-2H-1,4-oxazine): substitution at the 3-position prevented the N-polyfluoroalkylation by CF3CH2OSO2CF3. No particular difference was found between the two different heterocyclic systems in contrast with the reaction of these heterocyclic systems with C6F5Si(CH3)3. The discussion about the reaction mechanisms for both reagents are included.