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Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic Chemistry
Volume 39, 2009 - Issue 6
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Original Articles

Synthesis of Poly(Ethylene Glycol)–Supported (R)-BINOL Derivatives and Their First Application in Enantioselective Mukaiyama Aldol Reactions

, , , &
Pages 1012-1026 | Received 25 Aug 2008, Published online: 25 Feb 2009
 

Abstract

The Mukaiyama aldol reaction of 2-styryl-oxazole-4-carbaldehyde (1) as model substrate with S-ketene silyl acetal 2 catalyzed by poly(ethylene glycol)-supported binaphthyl-derived chiral titanium(IV) complexes afforded the corresponding aldol product in good to excellent yields and enantioselectivities up to 94% ee. The chemical yields and/or the enantioselectivities are enhanced by generating the active catalyst from Ti(OiPr)4, polymer-supported ligands (R)-6 or (R)-8, and chiral or achiral promoters. Pyrrolidine derivative (S)-13 and trifluoromethyl-substituted phenol 12 are the most efficient additives found.

Notes

a The ee was determined after the desilylation of 10.

b Result taken from Ref. 22.

c 60% of conversion.

d 2 equivalents of BINOL ligand (R)-8 and 1 equivalent of Ti(OiPr)4.

a 10 mol% of the ligand was used.

b The ee was determined after the desilylation of 10.

c Ca. 80% of conversion.

d Ca. 85% of conversion.

e 15 mol% of the ligand was used.

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