Volume 53, Issue 48 pp. 13258-13263
Communication

Enantio- and Diastereoselective Access to Distant Stereocenters Embedded within Tetrahydroxanthenes: Utilizing ortho-Quinone Methides as Reactive Intermediates in Asymmetric Brønsted Acid Catalysis

M. Sc. Chien-Chi Hsiao

M. Sc. Chien-Chi Hsiao

Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074 Aachen (Germany)

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M. Sc. Hsuan-Hung Liao

M. Sc. Hsuan-Hung Liao

Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074 Aachen (Germany)

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Prof. Dr. Magnus Rueping

Corresponding Author

Prof. Dr. Magnus Rueping

Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074 Aachen (Germany)

Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074 Aachen (Germany)Search for more papers by this author
First published: 06 October 2014
Citations: 227

H.-H.L. and C.-C.H. were supported by DAAD fellowships. We gratefully acknowledge financial support from the DFG.

Graphical Abstract

Procedures for the Brønsted acid catalyzed asymmetric synthesis of 9-substituted tetrahydroxanthenones and 3,9-disubstituted tetrahydroxanthenone derivatives have been developed. The procedures are based on the in situ generation of ortho-quinone methides and their subsequent reaction with 1,3-dicarbonyl compounds. The reaction provides products with a high level of asymmetric induction.

Abstract

A protocol for the highly enantioselective synthesis of 9-substituted tetrahydroxanthenones by means of asymmetric Brønsted acid catalysis has been developed. A chiral binol-based N-triflyphosphoramide was found to promote the in situ generation of ortho-quinone methides and their subsequent reaction with 1,3-cyclohexanedione to provide the desired products with excellent enantioselectivities. In addition, a highly enantio- and diastereoselective Brønsted acid catalyzed desymmetrization of 5-monosubstituted 1,3-dicarbonyl substrates with ortho-quinone methides gives rise to valuable tetrahydroxanthenes containing two distant stereocenters.

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