Preparation of Mesoporous Silica-Supported Chiral Amino Alcohols for the Enantioselective Addition of Diethylzinc to Aldehyde and Asymmetric Transfer Hydrogenation to Ketones

Md Eaqub Ali,Shaheen M Sarkar,Mashitah Mohd Yusoff,Md Lutfor Rahman

doi:10.1155/2015/381836

Md Eaqub Ali, Shaheen M Sarkar + Show 2 more

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https://doi.org/10.1155/2015/381836

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Abstract

Optically active (−)-ephedrine, (−)-norephedrine, and (−)-prolinol were immobilized onto cubic mesoporous MCM-48 silica. The immobilized amino alcohols served as a heterogeneous chiral catalyst for the asymmetric addition of diethylzinc to aldehydes and transfer hydrogenation to ketones. The developed catalytic process yielded optically enriches secondary aromatic alcohols with 92–99% conversion and 70–82% enantioselectivity.

Highlights

Synthesis of optically active secondary alcohols through the asymmetric addition of organozinc reagent to aldehydes and transfer hydrogenation of ketones is an important chemical process in industry and drugs’ synthesis research [1,2,3,4,5,6,7,8,9,10]
Soai and coworkers have reported asymmetric addition of diethylzinc reagent to aldehyde catalyzed by silica gel-supported ephedrine [41]
The immobilization of optically active (−)-ephedrine, (−)norephedrine, and (−)-prolinol onto MCM-48 silica was performed through two steps as shown in Scheme 1

Summary

Introduction

Synthesis of optically active secondary alcohols through the asymmetric addition of organozinc reagent to aldehydes and transfer hydrogenation of ketones is an important chemical process in industry and drugs’ synthesis research [1,2,3,4,5,6,7,8,9,10]. Covalent immobilization of chiral catalysts onto insoluble supports has attracted much interest [13,14,15,16,17] since it provides an easy separation of products from the catalysts without tedious experimental workup, enabling an efficient recovery of the spent catalyst. It prevents the intermolecular aggregations of the active species because of their rigid structures, which do not swell or dissolve in organic solvents and often exhibit superior thermal and mechanical stability under the catalytic conditions. The immobilization of catalysts onto inorganic supports has been poorly reported [20,21,22]

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