Carbonyls catalytic oxidative substitution

The most widely employed methods for the synthesis of nitrones are the condensation of carbonyl compounds with A-hydroxylamines5 and the oxidation of A+V-di substituted hydroxylamines.5 9 Practical and reliable methods for the oxidation of more easily available secondary amines have become available only recently.10 11 12 13. These include reactions with stoichiometric oxidants not readily available, such as dimethyldioxirane10 or A-phenylsulfonyl-C-phenyloxaziridine,11 and oxidations with hydrogen peroxide catalyzed by Na2W044 12 or Se02.13 All these methods suffer from limitations in scope and substrate tolerance. For example, oxidations with dimethyldioxirane seem to be limited to arylmethanamines and the above mentioned catalytic oxidations have been reported (and we have experienced as well) to give... 

Homogeneous Catalytic Oxidation with Phosphine-Substituted Complexes of Rhodium Carbonyl Clusters... 

Voorhoeve et al. (14,30) have also stressed that the catalytic activity of perovskites is influenced by their stoichiometry. A simple way of varying the oxidation state of the ion at the position B is by substitution of the A ion by a different ion with an oxidation state other than 3. This method has been used by several authors (9, 62, 88, 96, 179-181) to understand the role of the 3orbital occupancy in the LaM03 series on the catalytic oxidation of CO. For M = Co the appearance of Co2+ ions by introduction of Ce4+ in position A enhances the rate of oxidation of CO, whereas the presence of Co4+ ions by substitution with Sr2+ reduces the rate. The explanation for this behavior has been given by assuming that CO is bonded to the transition-metal ion as a carbonyl, as occurs on metals (182), with donation of the carbon lone pair into the empty 3dzi orbital of M to form a cr-bond accompanied by back-donation of the f2g electrons of the metal to the antibonding rr-orbital of CO. It should be noted that the dz2 orbital is the lowest et level for the M3+ ions at the surface, and in order to have a partially empty dzi level, the occupation of all the et levels must be below unity. 

Alkyl halides are usually considered to be less suitable for double carbonylation because of the possibility of the direct reaction of alkyl halides with nucleophiles and of instability of alkyl-transition metal complexes involved in the catalytic process. However, allylic halides were found amenable to double carbonylation promoted by zerovalent palladium complex. It is well known that allylic halides undergo ready oxidative addition with a Pd(0) species to produce Tj -allylpalladium halide complexes. Thus, it was reasoned that the double carbonylation process might be realized if CO insertion into the aUyl-palladium bond proceeds before attack of amine on the 17 -allylpaUadium halide takes place. On the basis of fundamental studies on the behavior of i7 -allylpalladium halide complexes with CO and secondary amines, double carbonylation processes of substituted aUyl halides to give a-keto amides in high yields have recently been achieved (Eqs. 15 and... 

Condensation of phenols with glyoxylic acid in basic media to furnish substituted mandelic acids, which yield the corresponding aldehyde on homogeneous catalytic oxidative de-carbonylation. Information regarding the process is mostly confined to patent literature (Eq i 43) 126,127,128 conversion of phenol to p-hydroxybenz-... 

The Keglevich group has continued to deal with environmentally friendly and P-heterocyclic chemistry. The solid liquid phase alkylation of P=0-functionalised CH acidic compounds was accomplished under phase transfer catalytic and microwave (MW) conditions." a-Hydroxy-benzylphosphine oxides were synthesized by the addition of diphenylphosphine oxide to the carbonyl group of substituted benzaldehydes under MW conditions." The double Kabachnik-Fields (phospha-Mannich) reaction was utilized in the preparation of bis(phosphinoxidomethyl)amines. The Diels Alder cycloadditions of 1,2-dihydrophosphinine oxides and subsequent... 

The versatility of the PCH2/KI catalytic system is further demonstrated by its ability to catalyze the oxidative carbonylation of primary amines to symmetrically substituted ureas (Eq. 51), still under mild conditions (100 °C, 16 atm of CO, 4 atm of air in DME as the solvent) and with unprecedented catalytic efficiencies for this kind of reaction (up to ca. 2500 mol of product per mol of Pd) [274,275]. In some cases, working in the presence of an excess of CO2 (40 atm) had a beneficial effect on the reaction rate and product selectivity. 

Adogen has been shown to be an excellent phase-transfer catalyst for the per-carbonate oxidation of alcohols to the corresponding carbonyl compounds [1]. Generally, unsaturated alcohols are oxidized more readily than the saturated alcohols. The reaction is more effective when a catalytic amount of potassium dichromate is also added to the reaction mixture [ 1 ] comparable results have been obtained by the addition of catalytic amounts of pyridinium dichromate [2], The course of the corresponding oxidation of a-substituted benzylic alcohols is controlled by the nature of the a-substituent and the organic solvent. In addition to the expected ketones, cleavage of the a-substituent can occur with the formation of benzaldehyde, benzoic acid and benzoate esters. The cleavage products predominate when acetonitrile is used as the solvent [3]. 

Varieties of primary and secondary alcohols are selectively oxidized to aldehyde or carbonyl compounds in moderate to excellent yields as summarized in Table 3. As can be seen, /(-substituted benzyl alcohols (e.g., -Cl, -CH3, -OCH3, and -NO2) yielded > 90% of product conversion in 3-4 h of reaction time with TOP in the range of 84-155 h (entries 2-5, Table 3), Heterocyclic alcohols with sulfur- and nitrogen-containing compoimds are found to show the best catalytic yield with TOP of 1517 and 902 h for (pyrindin-2-yl)methanol and (thiophene-2-yl) methanol, respectively (entries 9 and 10, Table 3). Some of aliphatic primary alcohols (long chain alcohols) and secondary alcohols (cyclohexanol, its methyl substituted derivatives and norboman-2-ol) are also selectively oxidized by the membrane catalyst (entries 11-14 and 15-17, Table 3) with TOP values in the window of 8-... 

The discovery that additions of catalytic amounts of CoCl2, activated carbon, or metals on metal oxide or carbon supports are extremely effective in labilizing carbonyl groups in Fe(CO)5 is thus particularly noteworthy. Stepwise substitution products Fe(CO)5 x(CNR)x (x = 1-5) have been obtained in high yield with short reaction times using these catalysts (see Table III) (759). 

A catalytic amount of hydrobromic acid with an excess of hydrogen peroxide is found to be an effective reagent for the facile regeneration of carbonyl compounds from their 1,3-dithiane and 1,3-dithiolane derivatives.136 Bromide-assisted oxidation of substituted phenols with hydrogen peroxide, catalysed by heterogenous WO42-ions, resulted in the formation of p-quinols and their ethers in almost quantitative yields.137... 

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