The Methoxycarbonylation of Vinyl Acetate Catalyzed by Palladium Complexes of [1,2‐Phenylenebis(methylene)]bis[di(tert‐butyl)phosphine]

Palladium complexes of [1,2‐phenylenebis(methylene)]bis[di(tert‐butyl)phosphine] ( 1 ) catalyze the methoxycarbonylation of vinyl acetate (= ethenyl acetate) in the presence of methanesulfonic acid (Scheme 1). High selectivities to ester products can be obtained if free phosphine ligand is in excess over the amount of added acid (Table 1). Selectivities to methyl 2‐acetoxypropanoate, a precursor to lactate esters, can be as high as 3.6 : 1 at low temperature and pressure (Table 2). Replacing ^tBu by ⁱPr groups leads to less‐active catalysts and lower selectivities to the branched product. Replacing the phenylene moiety by a naphthalenediyl moiety also gives lower activity, but with similar selectivity to the phenylene‐based analogues. Linear hydrocarbon‐chain linkers as the backbone instead of the phenylenebis(methylene) linker leads to poor catalysis, except for a propane‐1,3‐diyl linker, which gives good rates but poor branched selectivity (Table 5). The effect of different reaction conditions on the catalysis is discussed. The syntheses of the new xylene‐based diphosphines 2 – 5 with one to four ⁱPr groups replacing the ^tBu groups at the P‐atoms of 1 and of the ligands 6 and 7 based on 1,2‐ and 2,3‐dimethylnaphthalene are also described (Schemes 2 and 3).     

Highly regioselective palladium-catalyzed methoxycarbonylation of styrene using chiral ferrocene- and biphosphole-based ligands

The methoxycarbonylation of styrene has been studied using Pd(OAc)₂/L/acid catalytic systems with L being chiral ferrocene- and biphosphole-based ligands. Good activities are obtained in mild conditions. Chemoselectivities and regioselectivities (up to 98% in favour of the branched isomer) are excellent but enantioselectivities remain moderate (ee up to 17%).     

Systematic Study of the Asymmetric Methoxycarbonylation of Styrene Catalyzed by Palladium Systems Containing Chiral Ferrocenyl Diphosphine Ligands

We present the first systematic study of the Pd‐catalyzed asymmetric methoxycarbonylation of styrene in the presence of chiral ferrocenyl phosphine ligands. The reaction conditions were optimized, and a screening of different catalyst precursors was performed. A number of 1,1′‐bis(phosphino)ferrocenes of the Mandyphos, Josiphos, Walphos, and Taniaphos types were tested in combination with [PdCl₂(NCPh)₂], in the presence of TsOH as the acid source. These systems afforded high enantioselectivities, although the regioselectivity of the reaction was found to be in favor of the (undesired) linear ester. The catalytic system made with the Josiphos ligand 1 gave rise to an enantiomeric excess (ee) of 86%.     

Methoxycarbonylation of propylene oxide: A new way to β-hydroxybutyrate

The methoxycarbonylation of propylene oxide (PO) to methyl β-hydroxybutyrate (MHB) catalyzed by dicobaltoctacarbonyl ([Co₂(CO)₈]) and 3-hydroxypyridine (3-OH-Py) in methanol system has been studied. The effects of different additives, the molar ratio of 3-OH-Py:Co₂(CO)₈, temperature, carbon monoxide (CO) pressure, reaction time on the conversion and selectivity have been investigated. The conversion of propylene oxide is 80.4%, and the yield of methyl β-hydroxybutyrate is 74.9% with selectivity 93.2% when the reaction is carried out for 16 h at 80 °C and 6.0 MPa of CO in methanol, with 0.125 mmol of Co₂(CO)₈, 0.25 mmol of 3-OH-Py. The mechanism of this catalytic reaction has also been proposed.     

Stereoselective synthesis of (Z)-β-fluoro-α,β-unsaturated esters from (Z)-2-fluoro-1-alkenyliodonium salts

(Z)-β-Fluoro-α,β-unsaturated esters were stereoselectively synthesized from (Z)-2-fluoro-1-alkenyliodonium salts by the Pd-catalyzed methoxycarbonylation reaction. The reaction proceeded at room temperature and various functional groups on the substrate can tolerate the reaction conditions.     

Selectivity for the methoxycarbonylation of ethylene versus CO---ethylene copolymerization with catalysts based on C4-bridged bidentate phosphines and phospholes

The C₄-bridged phospholes 11,12-bis(2,3,4,5-tetramethylphospholylmethyl)-9,10-dihydro-9,10-ethano-anthracene (cis, 4a; trans, 4b) and diphosphines 11,12-bis(diphenylphosphinomethyl)-9,10-dihydro-9,10-ethano-anthracene (cis, 5a; trans, 5b) and their corresponding palladium complexes [(P---P)PdCl₂] (6a–d) have been prepared and characterized. Single-crystal X-ray analyses of 6a–d have been undertaken and they reveal that 4a and b and 5a and b coordinate in a bidentate manner forming seven-membered chelate rings with natural bite angles between 98.62 and 100.30°. The palladium-catalyzed carbonylation of ethylene has been studied using 4a and b and 5a and b. Catalyst mixtures generated from 4a and b, palladium acetate and methanesulfonic acid are selective for the copolymerization of ethylene with carbon monoxide, generating low molecular weight polymers. Surprisingly, the activity of catalyst systems based on cis-(4a) is markedly higher than that based on its trans-isomer, 4b. The marked influence of the nature of the four-carbon tether is highlighted by comparative catalyst testing with [{1,4-bis(2,3,4,5-tetramethylphospholyl)butane}Pd(OAc)₂], which rapidly decomposes under the conditions used for copolymerization. In contrast, under identical conditions catalyst mixtures formed from 5a and b show a marked dependence of the selectivity on the stereochemistry of the ethano-anthracene tether, the former generating a low molecular weight copolymer while the latter generate mainly methyl propanoate. Interestingly, polyketone generated from catalysts based on bisphosphole 4a has a markedly higher average molecular weight than that formed using its diphenylphosphino counterpart, 5a.     

光促进温和条件下烯烃的氢甲酯化反应

在紫外光照射下烯烃的氢甲酯化反应能在常温常压条件下完成,系统地研究了不同钴盐催化剂的反应规律及酸碱性对反应的影响.发现醋酸钠可大大提高反应的选择性及产率,提出了醋酸钠作用的初步机理,即对反应体系酸碱性的调节及醋酸钠与催化剂的相互作用.     

Photopromoted methoxycarbonylation of olefin with methyl formate by Co（OAc）2

The photopromoted methoxycarbonylation of olefin with methyl formate catalyzed by Co(OAc)2 at ambient conditions has been carried out.The results indicated that the reaction activity increased with the increasing temperature.Methyl formate decomposed into CO and CH_3OH firstly under irradiation,and then the methoxycarbonylation of olefin proceeded under catalysis of Co(OAc)_2. The mechanism of methyl formate participating in the methoxycarbonylation is verified by the IR analysis and the labeling experiments of CD_3OD and CH_3~(18)OH.