Butene catalysts, platinum complexes

Asymmetric hydrosilylation of prochiral olefins, e.g. 1,1-disubstituted olefins, catalyzed by chiral phosphine complexes of platinum(II) [21], nickel(II) [22], and palladium(II) [23] has been reported. When a platinum complex of the type [L PtCl2]2, where L stands for (/ )-benzylmethylphenylphosphine (BMPP), was used as catalyst, methyldichlorosilane, but not trichlorosilane, reacted satisfactorily- with a-methylstyrene, 2,3-dimethyl-l-butene, and 2-methyl-l-butene to give the corresponding optically active addition products, RMeC HCH2SiMeCl2, R = Ph, /-Pr,... 

Diboration of a,/ -unsaturated ketones is promoted by platinum(O) complexes. Reaction of 4-phenyl-3-buten-2-one with bis(pinacolato)diboron in the presence of a platinum catalyst affords a boryl-substituted (Z)-boron enolate, that is, a 1,4-diboration product, in high yield with high stereoselectivity (Scheme 8). The isolated boron enolate is easily hydrolyzed by exposure to water, giving / -boryl ketones in high yields.66 Similar diboration of a,/ -unsaturated ketones has also been achieved with Pt(bian)(dmfu) (bian = bis(phenylimino)acenaphthene, dmfu = dimethyl fumarate).67 Although the... 

Scheme 1 a The [2 + 2] cycloaddition product of prochiral trans 2-butene with Si dimers of the Si(100) surface leads to chiral adsorbate complexes, b Hydrogenation of prochiral a-keto esters over platinum is a heterogeneously catalyzed reaction leading to chiral alcohols. Using cinchonidin as chiral modifier makes this surface reaction enantioselective. In a similar fashion, TA-modified nickel is a highly enantioselective catalyst for /3-keto ester hydrogenation... 

ATES), (ABCR), benzoylperoxide (BPO), (Fluka), dibutyltin dilaurate (DBTDL), (Merck), platinum methylvinylcyclosiloxane complex (PCO 85), (ABCR), were used as received. Diethyleneglycol bis-allylcarbonate (XR 80), (Essilor) was purified on a silica gel column. Butenylphenylcarbonate (BPC) was prepared by reaction of phenyl chloroformate with 3-buten-l-ol under phase transfer catalysis conditions (13,15). Precursors PSIa, PSIb and PSIc (Scheme 1) were prepared by cohydrosilylation with PMHS of both ATES and BPC in various relative proportions. The hydrosilylation reactions were carried out in dry toluene at 60°C with a Pt complex catalyst ([-CH=CH2]/[SiH] = 1.1 [Pt]/[SiH] = 5.10-4). 

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