Reactions of salicylaldehyde with tris(pentaf luorophenyl)silanes and secondary amines

Abstract

Reactions of tris(pentafluorophenyl)silanes RSi(C 6 F 5 ) 3 with salicylaldehyde and second ary amines were studied. The reactions afforded α pentafluorophenyl substituted amines. Si lanes RSi(C 6 F 5 ) 3 (R = Me, Ph, C 6 F 5 , CH 2 CH=CH 2 , and CH=CH 2 ) were found to be efficient reagents for transfer of the C 6 F 5 group to the iminium cation generated from salicyl aldehyde and amine. However, tris(pentafluorophenyl)phenylethynyl and tris(pentafluoro phenyl)silanes were not able to serve as a source of a fluorinated substituent because of competitive transfer of acetylenide fragment or hydride.

Activation of Pentafluorophenylsilanes by Weak Lewis Bases in Reaction with Iminium Cations

“…While considering trimethylsilyl derivatives, the acetate anion is the weakest competent activating Lewis base employed so far, as was demonstrated by Mukaiyama and co-workers for the transfer of a trifluoromethyl group onto aldehydes and electron-poor imines. − On the other hand, we have recently reported that an increase of silicon Lewis acidity can be achieved by introducing the electron-withdrawing pentafluorophenyl groups. − In this respect, it becomes interesting to find optimal conditions for the application of weak Lewis bases for activating silicon reagents in C−C bond forming reactions.…”