Synthesis of Chiral Pyridylphenols for the Enantioselective Addition of Diethylzinc to Aldehydes |
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Authors: | Pei‐Shan Wu Chinpiao Chen |
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Affiliation: | Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan, Republic of China |
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Abstract: | Chiral 8‐substituted 2‐(8,10,10‐trimethyl‐6‐aza‐tricyclo[7.1.1.02,7]undeca‐2(7),3,5‐trien‐5‐yl)‐phenols were prepared from a high enantiopurity (>97% ee) of (1R)‐(+)‐α‐pinene, and assessed in the enantioselective addition of diethylzinc to substituted benzaldehydes, giving the (S)‐alcohols with enantiomeric excess ranging from 33% to 89%. Interestingly, in all cases, except for those of ortho‐chlorobenzaldehyde, ortho‐ and para‐methoxybenzaldehydes, the ee was >71%. The plot of the Hammett substitution constants vs. enantiomeric excess of the diethylzinc addition to either the ortho‐ or para‐substituted benzaldehydes shows a linear correlation. |
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Keywords: | Enantioselective catalyst Diethylzinc Asymmetric alkylation Chiral ligand Enantiomeric excess |
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