Chiral Phosphoric Acid Catalyzed Enantioselective Synthesis of β-Amino-α,α-difluoro Carbonyl Compounds
摘要:
A biphenol-based chiral phosphoric acid bearing a 9-anthryl group at each of the 3,3'-positions catalyzed the asymmetric Mannich-type reaction of N-Boc Imine with difluoroenol silyl ethers In the presence of MS3A In THF to afford beta-amino-alpha,alpha-difluoroketones In good yields and with excellent enantioselectivities. Optically pure 3,3-difluoroazetidin-2-one was readily synthesized from the Mannich-adduct.
A Highly Enantioselective Mannich-Type Reaction of Glycine Schiff Base Catalyzed by a Cinchoninium Salt
作者:Zhonglin Tao、Arafate Adele、Xiang Wu、Liuzhu Gong
DOI:10.1002/cjoc.201400453
日期:2014.10
A chiral phase‐transfer catalyst, derived from the combination of cinchona alkaloid backbone and BINOL skeleton, enabled a Mannichreaction of glycine Schiff base with N‐Boc‐imines to generate α,β‐diamino acid derivatives in excellent yields (up to 99%) and with high diastereo‐ and enantioselectivities (up to>20:1 dr, 96% ee).
Asymmetric phase-transfer catalysis was first applied to the synthesis of chiral N,S-acetals by using amino acid-based bifunctional thiourea-ammonium salt catalysts. The reaction could be performed on the gram scale to give up to 93% ee and 99% yield with a catalyst loading as low as 0.1 mol % within 5 min.
Enantioselective Mannich reaction of γ-malonate-substituted α,β-unsaturated esters with N-Boc imines catalyzed by chiral bifunctional thiourea-phosphonium salts
作者:Jiaxing Zhang、Gang Zhao
DOI:10.1016/j.tet.2018.12.052
日期:2019.3
A novel enantioselective Mannichreaction of γ-malonate-substituted α, β-unsaturated esters with N-protected arylaldimines was realized by using asymmetric phase-transfer catalysis (APTC). With amino acid-derived bifunctional thiourea-phosphonium salts as a catalyst, a series of enantio-enriched Mannich products could be synthesized under very mild and simple reaction conditions with high yields and
Enantioselective Cycloaddition of Styrenes with Aldimines Catalyzed by a Chiral Magnesium Potassium Binaphthyldisulfonate Cluster as a Chiral Brønsted Acid Catalyst
A chiral magnesium potassium binaphthyldisulfonate cluster, as a chiral Brønsted acid catalyst, was shown to catalyze an enantioselective cycloaddition of styrenes with aldimines for the first time. The strong Brønsted acidity of the catalyst precursors, which might dissolve drying agents and take up the leached Mg2+ and K+, serendipitously led to good enantioselectivity. Mechanistic aspects were supported
In the field of chiralBrønstedbase catalysis, a new generation of chiralcatalysts has been highly anticipated to overcome the intrinsic limitation of pronucleophiles that are applicable to the enantioselective reactions. Herein, we reveal conceptually new chiralBrønstedbasecatalysts consisting of two different organobase functionalities, one of which functions as an organosuperbase and the other