A Brønsted Acid Catalyst for the Enantioselective Protonation Reaction
作者:Cheol Hong Cheon、Hisashi Yamamoto
DOI:10.1021/ja8041542
日期:2008.7.1
A highly reactive and robust chiral Brønstedacidcatalyst, chiral N-triflyl thiophosphoramide, was developed. The first metal-free Brønstedacid catalyzed enantioselective protonation reaction of silyl enol ethers was demonstrated using this chiral Brønstedacidcatalyst. The catalyst loading could be reduced to 0.05 mol % without any deleterious effect on the enantioselectivity.
Development of a new Lewis base-tolerant chiral LBA and its application to catalytic asymmetric protonation reaction
作者:Cheol Hong Cheon、Tatsushi Imahori、Hisashi Yamamoto
DOI:10.1039/c0cc02492a
日期:——
A new Lewis base-tolerant LBA (LewisAcidAssistedBronstedAcid) derived from La(OTf)(3) and (S)-HOP has been developed as a new chiralBronstedacid. This acid has been successfully applied as a catalyst to asymmetric protonation reactions of silylenolethers of 2-substituted cyclic ketones.
Reaction of lithium enolates of 2-arylcycloalkanones 2 with (R,R)-aminoborane 1, prepared from (1R,2R)-1,2-diaminocyclohexane 4 and PhBCl2, gives the corresponding optically active ketones 3 with up to 93% ee; this is the first example of enantioselective protonation using a metal-containing chiral proton source.
Enantioselective Protonation of Silyl Enol Ethers Catalyzed by a Chiral Pentacarboxycyclopentadiene-Based Brønsted Acid
作者:Jun Li、Shaoyu An、Chao Yuan、Pingfan Li
DOI:10.1055/s-0037-1611849
日期:2019.7
The enantioselectiveprotonation of silyl enol ethers was realized in the presence of a pentacarboxycyclopenta-1,3-diene-based chiral Bronsted acid catalyst with water as an achiral proton source to give the corresponding α-aryl ketones in good yields and up to 75% ee.
Enantioselective Protonation of Silyl Enol Ethers and Ketene Disilyl Acetals with Lewis Acid-Assisted Chiral Brønsted Acids: Reaction Scope and Mechanistic Insights
Enantioselectiveprotonation is a potent and efficient way to construct chiral carbons. Here we report details of the reaction usingLewisacid-assisted chiral Bronsted acids (chiral LBAs). The 1:1 coordinate complex of tin tetrachloride and optically active binaphthol ((R)- or (S)-BINOL) can directly protonate various silylenolethers and ketene disilyl acetals to give the corresponding α-aryl ketones