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Pure Appl. Chem. Vol. 74, No. 1, pp. 123-128 (2002)

Pure and Applied Chemistry

Vol. 74, Issue 1

Bidentate Lewis acid catalysts in asymmetric synthesis*

Keiji Maruoka

Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan

Abstract: The chemistry of bidentate Lewis acids belongs to an unexplored field of science, and so far has been only poorly studied. This paper illustrates the design of several bidentate Al and Ti Lewis acids, and their successful application to selective organic synthesis, particularly to asymmetric synthesis. For example, a new, chiral bidentate Ti(IV) complex is successfully designed by adding commercially available Ti(OPri)4 and (S)-binaphthol sequentially to 2,2'-bis(tritylamino)-4,4'-dichlorobenzophenone in CH2Cl2, and can be utilized for simultaneous coordination to aldehyde carbonyls, thereby allowing the precise enantioface discrimination of such carbonyls for a new catalytic, practical enantioselective allylation of aldehydes with allyltributyltin. This chiral bidentate Ti(IV) catalyst exhibits uniformly high asymmetric induction as well as high chemical yields for various aldehydes. The present enantioselective allylation is highly chemoselective in the presence of other carbonyl moieties.

*Lecture presented at the 11th IUPAC International Symposium on Organometallic Chemistry Directed Towards Organic Synthesis (OMCOS-11), Taipei, Taiwan, 22-26 July 2001. Other presentations are presented in this issue, pp.1-186.



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