Oxidation platinum-catalysed

Before showing how direct peroxidation of active group works, it should be mentioned that platinum catalyses oxidation of alcohols at ambient temperature in aldehydes (provided they are primary). The exothermicity of the reaction is sufficient to cause the alcohol to combust by heating a thread of platinum at a high temperature. Note that 2-butanol (but not isopropanol) is classified in list B, producing peroxides that become expiosive at a certain concentration in the lists of peroxidable compounds set up by Du Pont de Nemours company (see p.261). 

An HP IR study of the platinum catalysed carbonylation of methanol to methyl formate, revealed that the catalyst precursor, ds-[Pt(PEt3)2Cl2] is converted into cis-[Pt(PEt3)2(CO)2] along with a cluster species, [Pt3(PEt3)3(CO) ] (n = 3 or 4) [95]. A mechanism involving oxidative addition of methanol to Pt(0) followed by CO insertion into the Pt-OMe bond was suggested. 

Nitric oxide reduction with ammonia. Lintz and co-workers78,79 have studied the platinum catalysed reduction of nitric oxide by ammonia in the region... 

The platinum-catalysed intramolecular domino annulation reaction of o-alkynylben-zaldehydes has been described as a versatile approach to naphthalenes with annulated carbocycles or heterocycles of various sizes (Scheme 32).94 A plausible mechanism for the platinum(II)-catalysed annulation reaction shows that the double annulation process most probably proceeds through the benzopyrylium cation (117), which results from the nucleophilic attack of the carbonyl oxygen at the alkyne, activated by the Lewis-acidic platinum salt. A subsequent intramolecular Huisgen-type 3 + 2-cycloaddition of the second alkyne is assumed to generate intermediate (118). Rearrangement to (119) and the formal 4 + 2-cycloaddition product (118) leads to the aromatized final (116), liberating the active catalyst. In the case of FeCl3 as the Lewis acid, we assume that intermediate (118) is oxidatively transformed to (121). 

Edye L.A., Meechan, G.V., and Richards, G.N., Platinum catalysed oxidation of sucrose, Carbohydrate Chem., 10, 11-23, 1991. 

Hexachloroplatinic acid in isopropanol (Speier s catalyst) is the most commonly used hydrosilylation catalyst because of its broad applicability and effectiveness at very low concentrations. A generally accepted mechanism for homogeneous platinum catalysed hydrosilylation involves reduction of Pt(IV) to Pt(II) by the silane, ligand substitution by the alkene, oxidative addition of SiH to the metal, rearrangement to a a-bonded complex and finally reductive elimination of the product and recycle of the catalyst 206 208. The basic mechanism is summarised in Scheme 2. 

R.H. VENDERBOSCH, W. PRINS, W.P.M. VAN SWAAJJ, Platinum catalysed oxidation of carbon monoxide as a model reaction in mass transfer measurements . Chemical Engineering Science, o. 53, no. 19, p. 3355-3366,1988. 

The direct electrooxidation of aqueous E>-g]uconic acid to l>arabinose on graphite has been performed in a very simple apparatus which may be suitable for practical application. The electrocatalytic oxidation of sucrose on smooth, lead-modified platinum electrodes has been examined with a view to finding experimental conditions for the selective electrosynthesis of value-added compounds. A paper in Bulgarian on the electrooxidation of diacetone-L-sorbose at low current densities in a nickel oxide electrolizer has been publi ed. The influence of the rize of palladium particles and their location on the support on their activity in the oxidation of glucose has been examined. An investigation of the effect of tonperature and pH on the platinum-catalysed oxidation of sucrose showed that changes in temperature affect mainly the reaction rate, where changes in pH alter the selectivity. ... 

The formation of D-glucaric acid by platinum-catalysed oxidation of D-gluconic acid has been noted in the previous section. Mono- and per-allyl ether derivatives of xylaric and galactaric acids have been prepared by treating the aldaric acid with allyl alcohol in the presence of an appropriate acid catalyst. Diallyl 3-0-allyl-2,4-0-methylenexylarate was obtained in good yield when 2,4-0-methylenexylaric acid reacted with allyl bromide in the presence of alkali. The reaction of 2,3,4-tri-O-acetylxylaryl dichloride with diazomethane has been mentioned in Chapter 7. 

Phenyl a-L-idopyranosiduronic acid and the 4-methylumbelliferyl analogue, required for the assay of a-L-iduronidase, were obtained from a-L-idopyranose penta-acetate by standard condensations followed by saponification of the ester groups and platinum-catalysed oxidation at C-6. The synthesis of 5-azido-5-deoxy-L-idofuranurono-6,3-lactone derivatives is mentioned in... 

The platinum-catalysed oxidation of several partially protected ketoses has been examined by Heyns s group > (see Chapter 16). 

Methods of determination of the configuration of bicyclo[2,2,l]-heptanols have been reviewed. The platinum-catalysed oxidation of bicyclo-[2,2,l]heptanediols, whose n.m.r. spectra are discussed, gives ° a number of different diketones and hydroxy-ketones. The n.m.r. spectra of adducts of cyclopentadiene with a-methyl-P-acetylacrylic acid, and of dimers of substituted cyclopentadienes, are noted. 

Finely divided (catalytic) forms of platinum are hazardous to handle if allowed to dry. Used Adams hydrogenation catalyst exploded while being sieved in air. It had been well washed, finally with water, and then air dried [1]. Manipulation of used catalyst on filter paper caused a violent explosion [2], The explosive catalysed oxidation of adsorbed hydrogen is suspected here. 

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],... 

In determining the diversity of reactions which may be catalysed by polyleucine, it has been shown that the oxidation of sulfides to sulfoxides can be performed, achieving excellent levels of asymmetric induction. Thus, when polyleucine is coated onto a platinum electrode, oxidation of sulfides to optically active sulfoxides has been achieved in 77% e.e. and 56% yield, (Scheme 11) [22]... 

Scheme 9.1. Oxidation of aldehydes at a platinum anode catalysed by macrocycle 5 in methanol.

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