Palladium complexes phosphite

Y. Kayaki, Y. Noguchi, S. Iwasa, T. Ikariya, R. Noyori, An Effitient Carbonylation of Aryl Halides Catalysed by Palladium Complexes with Phosphite Ligands in Supercritical Carbon Dioxide , Chem Commun. 1999, 1235-1236. 

The platinum complex is reasonably air stable, but the palladium complex is moderately air sensitive, turning to a black powder overnight if stored in air. Their solubilities are similar to those of the nickel analogue. There is a tendency for both the palladium and platinum complexes to lose a phosphite ligand on recrystallization. 

Metal carbon insertions of C02 occur in both main group and transition metal complexes.5,19 The reactions result in a strong M—O bond at the expense of a weak M—C bond (together with a C C a bond at the expense of a C O n bond). Insertion into t/weo-W(CO)5 CHDCHDPh gave the threo carboxylate, indicating retention of configuration at the o-carbon, as with CO insertion.29 Cis- RW(CO)4L (R = Me, Et or Ph) showed second-order kinetics toward C02 insertion, first order in anion and in C02. Replacement of CO by a phosphine or phosphite increased the insertion rate.30 Palladium catalysis of C02 insertion into unreactive Sn C bonds in allyl stannanes provided three isomeric tetra-carboxylates from tetraallyl tin. Attempted reactions of tetraalkyl, vinyl or aryl tin complexes did not proceed. Insertion into an intermediate rf -allyl palladium complex was suggested to lead to carboxylate products.31,32... 

Apart from palladacycles, a number of catalyst systems are currently known that show productivities up to 100,000 for Heck and Suzuki reactions of all kinds of aryl bromides. It is important to note that coupling reactions of electron-deficient aryl bromides (e.g., 4-bromoacetophenone), which are often used in academic laboratories, are not suitable as test reactions to judge the productivity of a new catalyst, because simple palladium salts without any Ugand give turnover numbers up to 100,000 with these substrates. Recently, palladium complexes in combination with sterically congested basic phosphines (e.g., tri-tcrt-butylphosphine), carbenes, and also phosphites led to productive palladium catalysts for the activation of various aryl chlorides. 

Wlemin, D., Jaffres, P.-A., Nechab, B. and Courivaud, F. (1997) Palladium complexes supported on hybrid organic-inorganic zirconium phosphite selectivity in the Heck reaction. Tetrahedron Lett., 38, 6581. ... 

The synthesis of (-)-A -acetyl-O-methylacosamine, " an amino sugar, is an interesting application of the process of cis-hydroxyamination catalyzed by palladium complexes of olefins developed by Trost and Sudhakar. Enantiomerically pure aldehyde 263 was first transformed to vinyl epoxide 264. The latter reacted smoothly with p-toluene sulfonyliso-cyanate in the presence of 1-3 mol% of palladium and 6-18 mol% of tiiisopropyl phosphite in THF at room temperature. As thermal reaction favored 0-aIkylation, these conditions led exclusively to A-p-toluenesulfonyl-2-oxazolidone 265 as shown in Scheme 60. 

Reactions.—Desulphurization of thiirans to alkenes remains an important strategy for the preparation of hindered alkenes, e.g. (14), and is the most typical thiiran reaction. Phosphines and phosphites are the reagents that are most often used. Lithium reagents desulphurize rra s-2,3-diphenylthiiran to ( )-stilbene, while the ds-isomer is converted into a 1 1 mixture of (Z)-stilbene and the two isomers of tr-mercaptostilbene. 2-Phenylthiiran is desulphurized by cf-metallated isocyanides. Thermal extrusions of sulphur include the conversion of (15) into (16), amongst others. Desulphurizations using zinc and acetic acid, molybdenum or palladium complexes, and the oxaziridine (17) have been reported. 

Maleic anhydride monomer cont.) oxime adducts, 228 palladium complexes, 213 peracid formation, 246 phenols photochemical reaction, 180 phosphine reactions, 230 phosphite reactions, 206 photo-adduct applications, 213 photo-adduct sterochemistry, 182, 183, 192-194 photochemical dimerization, 188 photochemical polymerization, 195, 239, 241-243, 247, 248... 

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