Hydrosilylation catalytic asymmetric

Asymmetric hydrosilylation can be extended to 1,3-diynes for the synthesis of optically active allenes, which are of great importance in organic synthesis, and few synthetic methods are known for their asymmetric synthesis with chiral catalysts. Catalytic asymmetric hydrosilylation of butadiynes provides a possible way to optically allenes, though the selectivity and scope of this reaction are relatively low. A chiral rhodium complex coordinated with (2S,4S)-PPM turned out to be the best catalyst for the asymmetric hydrosilylation of butadiyne to give an allene of 22% ee (Scheme 3-20) [59]. 

Although it is not a catalytic asymmetric hydrosilylation, chirality transfer was reported in the palladium-catalyzed addition of an enantiomerically enriched hydrosilane to norbornene.76... 

In conclusion, catalytic asymmetric hydrosilylation has been developed as one of the most efficient methods of asymmetric functionalization of carbon-carbon double bonds. The asymmetric hydrosilylation is reaching very high level in terms of both catalytic activity and enantioselectivity, and it is expected to be applied to industrial production of useful chiral molecules in the near future. 

Catalytic asymmetric hydrosilylation of prochiral olefins has become an interesting area in synthetic organic chemistry since the first successful conversion of alkyl-substituted terminal olefins to optically active secondary alcohols (>94% ee) by palladium-catalyzed asymmetric hydrosilylation in the presence of chiral monodentate phosphine ligand (MOP, 20). The introduced silyl group can be converted to alcohol via oxidative cleavage of the carbon-silicon bond (Scheme 8-8).27... 

Catalytic asymmetric hydrosilylation of terminal olefins has been developed, using palladium coordinated to the novel binaphthyl ligands (MOP). In all cases (MOPa-d), the enantioselectivity is excellent ( 90% e.e.). The products can be converted into the corresponding secondary alcohols with retention of configuration446. 

Rhodium-Catalyzed Asymmetric Hydrosilylation of Ketones. Complex 2 is a good catalyst for catalytic asymmetric hydrosilylation of ketones (eq 7). The reactions are carried out by using 1-naphthylphenylsilane at -40 °C in THF in the presence of 2 (1 mol%) for 3-4 days. Several types of ketones are hydrosilylated to afford optically active alcohols after acidic work-up. 

Asymmetric hydrosilylation has thus become one of the most useful methods for the preparation of optically active alcohols from alkenes [9,10]. Another important application of catalytic asymmetric hydrosilylation is the 1,4-hydros-ilylation of 1,3-dienes which efficiently produces optically active allyHc silanes. 

This review deals with recent advances in catalytic asymmetric hydrosilylation of olefins, carbonyl and imino compounds in the presence of transition metal complexes of chiral phosphine ligands with particular emphasis on the asymmetric reduction of prochiral carbonyl compounds, which has been extensively studied in the last few years by several research groups and proved to provide an effective reduction method for organic syntheses. 

In the preceding Sections it was described that chiral phosphine-rhodium complexes are effective in causing stereoselective addition of a hydrosilane to a variety of prochiral carbonyl compounds to give silyl ethers of the corresponding alkanols with fairly high enantiomeric bias at the carbon atom. The present section describes an application of the catalytic asymmetric hydrosilylation of ketones to the preparation of some new asymmetric bifunctional organosilanes. 

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