Asymmetric hydrosilylations of alkenes

Examples of asymmetric hydrosilylation of alkenes performed in the presence of chiral sulfur-containing ligands are much rarer in literature than... 

C-E Bond Formation through Asymmetric Hydrosilylation of Alkenes... 

Asymmetric Hydrosilylation of Alkenes. The palladium complex PdCl2[(/ )-(5)-PPFA] catalyzes the asymmetric hydrosilylation of norbornene, styrene, and 1,3-dienes (eq 3). The hydrosilylation of 1-phenyl-1,3-butadiene with Trichlorosilane proceeds regioselectively in a 1,4-fashion to give (Z)-1-phenyl-1-silyl-2-butene of 64% ee. 

M. Capka, Coll. Czech. Chem. Comm., 1977,42,3410. The asymmetric hydrosilylation of alkenes is reported in ref. 49. 

One of the most common methods for the preparation of enantiomerically enriched organosilanes is by palladium-catalysed asymmetric hydrosilylation of alkenes in the presence of trichlorosilane. This area has been dominated by the use of monodentate phosphorus-based ligands and, in particular, Hayashi s MOP ligand/palladium catalyst combination offers a high level of enantioselectivity. The MOP ligands include MeO-MOP (2.139), H-MOP ligands such as (2.140) ... 

As noted earlier in this chapter, the enantioselective hydrosilylation of olefins could be a useful method to prepare chiral, non-racemic alcohols. A.lthough the scope of highly enantioselective hydrosilylations is limited, high enantioselectivities have been obtained for the asymmetric hydrosilylation of alkenes and vinylarenes. A majority of the most selective chemistry has been conducted using a palladium catalyst containing an axially chiral monophosphine ligand. 

Asymmetric hydrosilylation of alkenes, catalysed by ferrocenylphosphine-palladium complexes, can be utilized in a synthesis of optically active alcohols from alkenes (Scheme 1). The initial optically active silane adducts are converted to alkyl pentafluorosilicates (1) which are then cleaved oxidatively, with retention of configuration, using peracid (c/. 3,132). Complex (2) was the best of several hydrosilylation catalysts examined using this, alcohols with enantiomeric purities of approx. 50% were obtained from norbornene and styrene as the alkenes. 

The asymmetric hydrosilylation of alkenes mentioned earlier (Scheme 1) can be used to prepare optically active bromides by halogenation of the alkyl-pentafluorosilicate intermediates (1) with inversion of configuration using N-bromosuccinimide. Treatment of organoboranes with ICl provides a rapid mild route from alkenes to anti-Markovnikov iodides (Scheme 37), although all three alkyl groups of the organoborane do not react with the ICl. " ... 

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