Synthesis 2004(9): 1439-1445  
DOI: 10.1055/s-2004-822364
PAPER
© Georg Thieme Verlag Stuttgart · New York

Functionalized BINOL Derivatives as Ligands for Enantioselectively Catalyzed Aldol Additions: Highly Enantioselective Synthesis of Chiral β-Hydroxy Thioesters

Reinhold Zimmer*a, Luise Schefziga, Anke Peritzb, Vjekoslav Dekarisa, Hans-Ulrich Reissiga
a Institut für Chemie, Freie Universität Berlin, Takustrasse 3, 14195 Berlin, Germany
Fax: +49(30)83855367; e-Mail: rzimmer@chemie.fu-berlin.de;
b Institut für Organische Chemie, Technische Universität Dresden, 01062 Dresden, Germany
Further Information

Publication History

Received 1 April 2004
Publication Date:
10 May 2004 (online)

Abstract

A series of 3,3′-disubstituted and 6,6′-disubstituted BINOL derivatives was synthesized and examined in typical titanium(IV) promoted aldol reactions. The model reaction of S-ketene silyl acetal 13 and aldehydes 12a and 12b revealed that 6,6′-dibromo-BINOL derivative (R)-6 is the ligand of choice for these transformations. Up to 97% yield with excellent enantioselectivity (ee > 97%) could be achieved. Scope and limitations were demonstrated using a series of aldehydes as substrates, which were generally transformed into their aldol adducts by the (R)-6/Ti(Oi-Pr)4 catalyst with good efficacy and high enantioselectivity.

19

The NMR signals of the electronically deficient dibromo derivative (R)-6 are generally shifted upfield when compared with the unsubstituted (R)-4.