Phosphino carboxylic acid ester functionalized carbosilane dendrimers: Nanoscale ligands for the Pd-catalyzed hydrovinylation reaction in a membrane reactor

Phosphino carboxylic acid ester terminated G0compounds Si{(CH2)3SiMe2(C6H4CH2OC(O)(CH2)nCH2PPh2}4(9a and 9b; n = 1, 2) and the carbosilane dendrimers Si{(CH2)3Si((CH2)3SiMe2(C6H4CH2OC(O)(CH2)nCH2PPh2)3}4(10a and 19b; n = 1, 2) have been prepared as hemilabile nanoscale ligands for the palladium-catalyzed codimerization of olefins. The hydrovinylation of styrene was carried out in a continuously operated nanofiltration membrane reactor. Under continuous conditions, the selectivity of the reaction is increased considerably. Monomeric model complexes and the dendritic catalysts were compared for their activity and selectivity in batch reactions. The Pd catalyst complexes were prepared in situ from the dendritic ligands and an (allyl)palladium(II) precursor

Selective hydrovinylation in a membrane reactor: use of carbosilane dendrimers with hemilabile P,O-ligands

Phosphino carboxylic acid ester terminated G0 compounds Si{(CH2)3SiMe2(C6H4CH2OC(O)(CH2)nCH2PPh2}4 (9a and 9b; n = 1, 2) and the carbosilane dendrimers Si{(CH2)3Si((CH2)3SiMe2(C6H4CH2OC(O)(CH2)nCH2PPh2)3}4 (10a and 10b; n = 1, 2) have been prepared as hemilabile nanoscale ligands for the palladium-catalyzed codimerization of olefins. The hydrovinylation of styrene was carried out in a continuously operated nanofiltration membrane reactor. Under continuous conditions, the selectivity of the reaction is increased considerably. Monomeric model complexes and the dendritic catalysts were compared for their activity and selectivity in batch reactions. The Pd catalyst complexes were prepared in situ from the dendritic ligands and an (allyl)palladium(II) precursor

Optically active transistion-metal complexes. 9.1 A general stereoselective route to a-chiral (R)-tricarbonyl (h6-ethylbenzene)chromium complexes. Novel organometallic phosphine catalysts for the asymmetric hydrovinylation reaction

Treatment of (R)-[{a-(dimethylamino)ethyl}-¿6-benzene]Cr(CO)3 with esters of chloroformic acid leads to stereoselective substitution of the dimethylamino group for a chloro substituent. The reaction can be extended to systems in which the chromium arene complex, after metalation, is diastereoselectively substituted in the ortho position with carbon and silicon electrophiles to generate planar chirality. The chloro group in turn can be replaced stereoselectively for various phosphorus, nitrogen, and oxygen nucleophiles. Both substitution reactions in the benzylic position proceed via retention of configuration. The addition of cyanide is not stereospecific. The phosphine derivatives are efficient catalysts for the enantioselective hydrovinylation of styrene to 3-phenyl-1-butene. X-ray crystal structures establish the absolute configuration of (R)-[(a-chloroethyl)¿6-benzene]Cr(CO)3, (R)-[{a-(diphenylphosphanyl)ethyl}-¿6-benzene]Cr(CO)3, and (pS,S)-[1-(a-cyanoethyl)-2-methyl-¿6-benzene]Cr(CO)3

Towards Perfect Asymmetric Catalysis: Additives and Co-catalysts

Vogl EM, Gröger H, Shibasaki M. Towards Perfect Asymmetric Catalysis: Additives and Co-catalysts. Angew. Chem. Int. Ed. 1999;38(11):1570-1577

Palladium complexes of phosphine functionalised carbosilane dendrimers as catalysts in a continuous flow membrane reactor

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