Enantioselective Diethylzinc Addition to Aromatic Aldehydes Catalyzed by Novel Ti(IV) Complex of Three-Dentate Chiral Sulfonamide Ligands

Abstract

The synthesis of several novel three-dentate sulfonamide alcohol ligands is described, starting from camphorsulfonyl chloride. The influence of temperature and ligand structure on the asymmetric addition of dietylzinc to aromatic aldehydes has been studied. Enantioselectivities up to 76% have been obtained.

Keywords:

• Aldehydes
• diethylzinc
• enantioselectivity
• sulfonamide alcohols

ACKNOWLEDGMENTS

Financial support from the Research Council of Shahid Beheshti University and the Catalyst Center of Excellence (CCE) is gratefully acknowledged.

Notes

^a GC yield on the mixture of the two enantiomers.

^b Ee was determined by GC using a chiral capillary column (HP-chiral).

^c Absolute configuration of the major enantiomer was determined by comparison with an authentic sample.

^d Without any Ti(OPrⁱ)₄.

^e With 10 mol% of benzoic acid.

^a Condition: −20°C, 40 h, and 15 mol% of 3a.

^b Measured as conversion percentage by GC.

^c Determined by capillary chiral GC analysis using the chiral column (HP-chiral).

^d Absolute configuration was determined by comparing the sign of specific rotation.^[ 7-10 ^] The major enantiomer in all cases had the S configuration.

^e With 10 mol% of benzoic acid.