HFPO Trimer-Based Alkyl Triflate, a Novel Building Block for Fluorous Chemistry. Preparation, Reactions and 19F gCOSY Analysis

Abstract

Triflate 4 , CF 3 (CF 2 ) 2 O-CF(CF 3 )CF 2 O-CF(CF 3 )CH 2 -OTf (R FO CH 2 OTf), of the HFPO trimer-based alcohol 3 (R FO CH 2 OH) is a novel highly fluorinated building block for fluorous chemistry. In analogy to similar polyfluorinated triflates with methylene spacer, its reactivity is limited to strong and soft nucleophiles. Whereas reactions with cyanide anion, phenolate anion, enolate of diethyl malonate or lithium salt of benzaldehyde bis(phenylsulfanyl)acetal were unsuccessful, the corresponding imidazole 5 , iodide 6 or azide 7 were prepared in good yields. Reaction of imidazole 5 with (perfluorohexyl)methyl triflate ( 9 ) afforded highly fluorinated non-crystalline imidazolium salt 8 , TfO - R FO CH 2 -(C 3 H 3 N 2 ) + -CH 2 C 6 F 13 - n , which could be employed as fluorous ionic liquid or intermediate for fluorous carbenes. Complete assignment of complex 19 F NMR spectra of all compounds employed was accomplished using 19 F gCOSY NMR method.