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DOI: 10.1055/s-2004-822364
Functionalized BINOL Derivatives as Ligands for Enantioselectively Catalyzed Aldol Additions: Highly Enantioselective Synthesis of Chiral β-Hydroxy Thioesters
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.
Keywords
binaphthalene - Aldol reaction - titanium - Sonogashira reaction - thioesters - bissteroidal ligand