Trimethylsilyl Bis(trifluoromethanesulfonyl)amide as an Effective Catalyst for the Friedel-Crafts Alkylation Reaction

Carbon-Carbon Bond Forming Reactions by using Bistrifluoromethanesulfonimide

“…31 The active species, formed by reaction of TFSI-H with allyltrimethylsilane, is TMSNTf 2 and this compound exhibits an enhanced Lewis acidity compared to TMSOTf. 15,19 However we failed to reproduce the 1,4-allylation of cyclohexenone 29, as the allylated ketone 32 was obtained in low yield (10%). The major product obtained was the allylated diketone 33 (mixture of two diastereomers, 40%), resulting from an initial 1,4-addition of allylsilane followed by a 1,4-addition of the intermediate silyl enol ether 34 to cyclohexenone 29 (Scheme 4).…”

Crucial Role of the Conjugate Base for Silyl Lewis Acid Induced Mukaiyama Aldol Reactions

“…The reaction of the activated aldehyde 4 and the silyl enol ether 2 generates the silyloxycarbenium intermediate 5a or 5b. [5] The intermolecular transfer of the silyl group to conjugate base X produces the metal aldolate 6 and the silyl Lewis acid (R Recently, we demonstrated that Me 3 SiNTf 2 [6][7][8][9] shows a strong catalytic activity for the Mukaiyama aldol reaction and the Sakurai-Hosomi allylation reaction. [10] The conjugate base, -NTf 2 , is well recognized as a strong electronwithdrawing and weakly coordinating counteranion, that is a ligand of low nucleophilicity.…”

The Search for Tolerant Lewis Acid Catalysts. Part 2. Enantiopure Cycloalkyldialkylsilyl Triflimide Catalysts.

“…In 1997, both our group and Mikami's group discovered that N-(trimethylsilyl)triflimide (Me 3 SiNTf 2 ) was an extremely efficient carbonyl activator. 5,6 We observed an unexpected reversal of thermodynamic acidity on going from the Br€ onsted acids (HOTf>HNTf 2 ) to the TMS derivatives (TMSOTf< TMSNTf 2 ), which was assigned to the larger size of the triflimide group as compared to triflate. 5 Also our group demonstrated that increasing the size of the alkyl substituents on silicon resulted in a significant increase of Lewis acidity.…”