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Published September 21, 1994 | public
Journal Article Open

Catalytic, Enantioselective Aldol Additions with Methyl and Ethyl Acetate O-Silyl Enolates: A Chiral Tridentate Chelate as a Ligand for Titanium(IV)


Asymmetric catalysis of the Mukaiyama aldol reaction has been reported with complexes derived from Al, B, Sn(II), and Ti(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).

Additional Information

© 1994 American Chemical Society. Received June 28, 1994. We are grateful to the Fannie and John Hertz Foundation for a Graduate Fellowship award to R.A.S. This research has been supported by a Beckman Young Investigator Award, a Camille and Henry Dreyfus New Faculty Award (NF-92-46), the Petroleum Research Fund (ACS-PRF 27091-G1), and a gift from the Medicinal Chemistry Research Unit at The Upjohn Company.

Attached Files

Supplemental Material - ja00098a065_si_001.pdf

Supplemental Material - ja8837.pdf


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August 20, 2023
August 20, 2023