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Metal-free catalytic C-Si bond formation in an aqueous medium. Enantioselective NHC-catalyzed silyl conjugate additions to cyclic and acyclic ?,?-unsaturated carbonyls.

ABSTRACT: A metal-free method for enantioselective conjugate addition of a dimethylphenylsilyl group to ?,?-unsaturated carbonyls is reported. Transformations are catalyzed by a chiral N-heterocyclic carbene (NHC), performed in an aqueous solution (3:1 mixture of water and tetrahydrofuran) and are operationally simpler to perform than the NHC-Cu-catalyzed variant. The chiral catalyst is generated from an enantiomerically pure imidazolinium salt (prepared in three steps) and a common organic amine base (dbu). NHC-catalyzed processes proceed with 5.0-12.5 mol % catalyst loading at 22 °C within 1-12 h, affording the desired ?-silyl carbonyls in 85:15 to >98:2 enantiomeric ratio and in 50% to >98% yield. Cyclic enones or lactones and acyclic ?,?-unsaturated ketones, esters, and aldehydes can be used as substrates.

SUBMITTER: O'Brien JM

PROVIDER: S-EPMC3097346 | biostudies-literature | 2011 May

REPOSITORIES: biostudies-literature

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Metal-free catalytic C-Si bond formation in an aqueous medium. Enantioselective NHC-catalyzed silyl conjugate additions to cyclic and acyclic α,β-unsaturated carbonyls.

O'Brien Jeannette M JM Hoveyda Amir H AH

Journal of the American Chemical Society 20110427 20

A metal-free method for enantioselective conjugate addition of a dimethylphenylsilyl group to α,β-unsaturated carbonyls is reported. Transformations are catalyzed by a chiral N-heterocyclic carbene (NHC), performed in an aqueous solution (3:1 mixture of water and tetrahydrofuran) and are operationally simpler to perform than the NHC-Cu-catalyzed variant. The chiral catalyst is generated from an enantiomerically pure imidazolinium salt (prepared in three steps) and a common organic amine base (db ...[more]

PMID: 21524126

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