Catalytic, Enantioselective Aldol Additions with Methyl and Ethyl Acetate O-Silyl Enolates: A Chiral Tridentate Chelate as a Ligand for Titanium(IV)
Citations Over TimeTop 1% of 1994 papers
Abstract
Asymmetric catalysis of the Mukaiyama aldol reaction has been reported with complexes derived from Al, B, Sn(II), and \nTi(IV). The levels of asymmetric induction for the addition of propionate-, isobutyrate-, and acetate-derived silyl thioketene acetals to aldehydes parallel those obtained with chiral-auxiliary-based methodologies. However, silyl ketene acetals derived from O-alkyl acetates uniformly provide aldolates possessing lower levels of asymmetric induction. We have initiated a study aimed at the design and synthesis of chiral Ti(IV) complexes that catalyze the enantioselective Mukaiyama aldol of O-trimethylsilyl, O-methyl, and O-ethyl ketene acetals with aldehydes. We report herein a catalyst that consists of a tridentate ligand derived from 3, Ti(O'^iPr)_4, and 3,5-di-tert-butylsalicylic acid. This catalyst (2-5 mol %) furnishes aldol adducts in good yields and high levels of asymmetric induction (88-97% ee).
Related Papers
- → Palladium(II)-Catalyzed Enantioselective C(sp3)–H Activation Using a Chiral Hydroxamic Acid Ligand(2014)259 cited
- → Highly enantioselective synthesis of β-hydroxy nitriles by the cyanomethylation of aldehydes using DPMPM as a chiral catalysts or ligand(1992)47 cited
- → Isosterically designed chiral catalysts: Rationale, optimization and their application in enantioselective nucleophilic addition to aldehydes(2020)10 cited
- → Functionalized Triarylcarbenium Ions as Catalysts in Mukaiyama Aldol Addition: Effects of Counter Ions and Silyl Groups on the Intervention of Silyl Catalysis(1998)19 cited
- → A short and efficient synthesis of N-Cbz-galantinic acid under promoter control on enantioselective acyclic stereoselection based on chiral oxazaborolidinone-promoted aldol reactions(2000)22 cited