Nucleophilic Substitution Reactions of Alkyl, Vinyl, and Aryl Trifluoromethanesulfonates.

摘要

The reaction of carbanion type nucleophiles with nitro substituted alkyl trifluoromethanesulfonate (triflate) esters has been shown to have very limited synthetic value. The usual result is formation of mixtures of tarry materials. Reaction of aryl triflates with various nucleophiles appears to be limited to nucleophilic attack at sulfonyl sulfur and, for strongly basic, hindered, nucleophiles, generation of benzyne. Neither type of reaction offers significant synthetic utility. Electron-transfer (ET) reactions of several classes of trifluoromethanesulfonyl derivatives were examined. For alkyl and aryl esters, the chemistry is very similar to that of the corresponding methanesulfonate esters. Trifluoromethanesulfonamides, however, display a behavior uniquely different from that of all other sulfonamides. They undergo reductive cleavage (to amine and triflite ion) much more easily than do methanesulfonamides, they cleave via a pre-equilibrium electron-transfer mechanism, and the substituent effect upon their rates of cleavage correlates extremely well with constants.