Oxidation palladium iodide

The reaction of alcohols with CO can also be catalysed by palladium iodides, and various ligands or solvents. Acetic acid is prepared by the reaction of MeOH with CO in the presence of a catalyst system comprising a palladium compound, an ionic iodide compound, a sulfone solvent at conditions similar to those of the rhodium system (180 °C, 60 bar), and, in some cases, traces of a nickel-bipyridine compound were added. Sulfones or phosphine oxides play a stabilising role in preventing metal precipitation [26], Palladium(II) salts catalyse the carbonylation of methyl iodide in methanol to methyl acetate in the presence of an excess of iodide, even without amine or phosphine co-ligands platinum(II) salts are less effective [27],... 

Pdl2 PALLADIUM IODIDE 1314 PuOl PLUTONIUM IODIDE OXIDE 1356... 

Many methods are available for the removal of oxygen from A -oxides, samarium iodide, chromous chloride, stannous chloride with low-valent titanium, ammonium formate with palladium, and catalytic hydrogenation all do the job at room... 

The oxidative addition of an aryl iodide to a zerovalent complex such as [Pd(PPh3)4] gives tra s-[Pd(Ar)I(PPh3)2] having a palladium-aryl and a palladium-iodide bond indeed, this is one of the oldest examples of oxidative addition of aryl iodide to Pd(0) complex (Eq. 1.1) [10]. 

The radionuclide with added carrier can be separated from most other long-lived radionuclides by precipitating silver or palladium iodide from dilute niuic acid solution. As indicated in Section 6.3.1, the oxidation state of radioiodine, of which there are several, must be well defined before a separation step can be trusted. Other purification techniques are solvent extraction of iodine oxidized to h into carbon tetrachloride followed by back extraction of the reduced iodide form into water, or sorption of 1 on anion-exchange resin followed by elution with a strong chloride solution (Kleinberg and Cowan 1960). These processes also lend themselves to concentrating the radionuclide from larger solution volumes to attain a lower detection limit. 

The pH dependence and mechanism of oxidation of iodide by chloramine-T have also been described. Palladium(ii) has been shown to be a catalyst in the oxidation of chloride by manganese(iii). 5 The complex MnCl + is formed during the reaction possibly via a chloride-bridged dinuclear intermediate with the catalyst. There is also evidence for Pd v formation. 

It was found, however, that if palladium iodide is used in place of the base under oxidative conditions under CO + CO2 pressure the following reaction occurs (Scheme 37). 

The complex catalytic cycle commences with oxidative palladium insertion on the aryl iodide bond. The following carbopalladation with norbornene creates a bulky intermediate that is not prone to p-hydride elimination and allows C-H activation of the ortho position of the aryl moiety. Subsequent oxidative addition of the alkyl iodide allows cross-coupling and elimination of the norbornene by retro-carbopalladation. The remaining intermediate 146 then undergoes aMizoroki-Heck reaction with the acrylate, which completes the catalytic process and furnishes the desired cinnamate 148 derivative. 

In a similar transformation, oxidative aminocarbonylation of alkyl- and aryl-substituted 1-alkynes is catalyzed by Pdl2/KI under relatively mild conditions to afford 2-ynamides 64 in good yield (Scheme 10.20) [60]. Nucleophilic secondary amines were required as amines of low basicity were unreactive and primary amines gave complex reaction mixtures. The key intermediate in the mono-aminocarbonylation was proposed to be an alkynyl palladium iodide that undergoes CO insertion followed by nucleophilic abstraction by amine to generate the product and Pd(0), which is reoxidized by iodine (2HI + I/2O2 = I2 + H2O). Small amounts of diaminocarbonylation product (maleic... 

Patents on the catbonylation of methyl chlotide [74-87-3] using carbon monoxide [630-08-0] in the presence of rhodium, palladium, and tidium complexes, iodo compounds, and phosphonium iodides or phosphine oxides have been obtained (26). In one example the reaction was conducted for 35... 

A synthetically useful virtue of enol triflates is that they are amenable to palladium-catalyzed carbon-carbon bond-forming reactions under mild conditions. When a solution of enol triflate 21 and tetrakis(triphenylphosphine)palladium(o) in benzene is treated with a mixture of terminal alkyne 17, n-propylamine, and cuprous iodide,17 intermediate 22 is formed in 76-84% yield. Although a partial hydrogenation of the alkyne in 22 could conceivably secure the formation of the cis C1-C2 olefin, a chemoselective hydrobora-tion/protonation sequence was found to be a much more reliable and suitable alternative. Thus, sequential hydroboration of the alkyne 22 with dicyclohexylborane, protonolysis, oxidative workup, and hydrolysis of the oxabicyclo[2.2.2]octyl ester protecting group gives dienic carboxylic acid 15 in a yield of 86% from 22. 

Substantially more work has been done on reactions of square-planar nickel, palladium, and platinum alkyl and aryl complexes with isocyanides. A communication by Otsuka et al. (108) described the initial work in this area. These workers carried out oxidative addition reactions with Ni(CNBu )4 and with [Pd(CNBu )2] (. In a reaction of the latter compound with methyl iodide the complex, Pd(CNBu )2(CH3)I, stable as a solid but unstable in solution, was obtained. This complex when dissolved in toluene proceeds through an intermediate believed to be dimeric, which then reacts with an additional ligand L (CNBu or PPh3) to give PdL(CNBu )- C(CH3)=NBu I [Eq. (7)]. 

Other solutions to dealing with interferences in the detection of H O have included the use of a copperfll) diethyldithiocarbamate precolumn to oxidize the sample before it reaches the immobilized enzyme, as well as the use of a palladium/gold sputtered electrode which catalyzes the oxidation of hydrogen peroxide In addition, peroxidase has been used to catalyze the reaction between hydrogen peroxide and iodide ferrocyanide and organo-fluorine compounds Am-... 

Reaction with Propargyl Halides. The indium-mediated coupling of propargyl bromide with a variety of imines and imine oxides afforded homo-propargylamine derivatives in aqueous media under mild conditions.78 Propargylation of glyoxylic oxime ether in the presence of a catalytic amount of palladium(O) complex and indium(I) iodide in aqueous media was also studied (Eq.11.47).79... 

As reported in Scheme 1 the process involves a series of steps. The alkylpalladium species 1 forms through oxidative addition of the aromatic iodide to palladium(O) followed by noibomene insertion (4-7). The ready generation of complex 2 (8-11) from 1 is due to the unfavourable stereochemistry preventing P-hydrogen elimination from 1 (12). Complex 2 further reacts with alkyl halides RX to form palladium(IV) complex 3 (13-15). Migration of the R group to the... 

Recently, Larock and coworkers used a domino Heck/Suzuki process for the synthesis of a multitude of tamoxifen analogues [48] (Scheme 6/1.20). In their approach, these authors used a three-component coupling reaction of readily available aryl iodides, internal alkynes and aryl boronic acids to give the expected tetrasubsti-tuted olefins in good yields. As an example, treatment of a mixture of phenyliodide, the alkyne 6/1-78 and phenylboronic acid with catalytic amounts of PdCl2(PhCN)2 gave 6/1-79 in 90% yield. In this process, substituted aryl iodides and heteroaromatic boronic acids may also be employed. It can be assumed that, after Pd°-cata-lyzed oxidative addition of the aryl iodide, a ds-carbopalladation of the internal alkyne takes place to form a vinylic palladium intermediate. This then reacts with the ate complex of the aryl boronic acid in a transmetalation, followed by a reductive elimination. 

Meanwhile, Wacker Chemie developed the palladium-copper-catalyzed oxidative hydration of ethylene to acetaldehyde. In 1965 BASF described a high-pressure process for the carbonylation of methanol to acetic acid using an iodide-promoted cobalt catalyst (/, 2), and then in 1968, Paulik and Roth of Monsanto Company announced the discovery of a low-pressure carbonylation of methanol using an iodide-promoted rhodium or iridium catalyst (J). In 1970 Monsanto started up a large plant based on the rhodium catalyst. 

Palladium Paraformaldehyde Paraldehyde Pentaborane-9 Pentacarbonyliron Arsenic, carbon, ozonides, sulfur, sodium tetrahydridoborate Liquid oxygen Alkalies, HCN, iodides, nitric acid, oxidizers Dimethylsulfoxide Acetic acid, nitric oxide, transition metal halides, water, zinc... 

These compounds contain a furan ring fused to a benzene moiety in the 2,3-position. This synthesis was also described by Flynn et al. [73] and is shown in Scheme 25 involved the coupling of 2-iodo-5-methoxyphenol 104, 4-methoxyphenylethyne 105 to form the intermediate o-alkynylphenolate 106. Aryl iodide 107 was added to the phenolate in DMSO with heat. Oxidative addition, palladium(II)-induced cyclization and reductive elimination resulted in the product 108 with an 88% yield. 

A distannation product of 2-butyne-l,4-diol oxidatively cyclizes to provide 3,4-bis(stannyl)furan, which then undergoes palladium-catalyzed cross-coupling with an aryl iodide to give 3,4-diarylfuran (Scheme 31).152,153... 

---