Olefins hydroxylation

Otsuka K-76, a fungal product with strong anticomplement activity, was synthesized from the A/B bicyclic precursor of stemodin. The aromatic subunit was retrosynthetically disconnected to a symmetrical precursor. A surprising non-selectivity of olefinic hydroxylation by osmium tetroxide was noted. 

Some of the most remarkable achievements include microencapsulation in polystyrenes such as entrapped 0s04 for olefin hydroxylation (exploiting the interaction between n-electrons of benzene rings of the polystyrenes used as polymer backbones and the vacant orbitals of the catalysts) 5 polyurea-entrapped palladium (PdEnCat)6 for a multiplicity of C C forming reactions and the use of carboxylic acid-functionalized polymer (FibreCat).7 In general, however, metal leaching cannot be avoided. The PdEnCat catalyst, for instance, leaches some 4% of palladium per catalytic reaction run. 

One of the routes to epimestix>l begins with acylation of estradiol with benzoyl chloride to give the dibenzoate 5. Pyrolysis of the ester leads to formation of the 16,17-olefin. Hydroxylation by means of osmiiim tetroxide affords the cis-diol 7 due to the intermediacy of the cyclic osmate ester (6a)-, attack... 

Catalysis of oxidation reactions will continue to be of enormous importance in the future. Areas that continue to be of active interest are the development of efficient methods for the direct epoxidation of olefins, hydroxylation and substitution of aromatics as well as the selective oxidation of alkanes. The application of methods developed for industrial chemicals to the synthesis of more complex molecules is worthy of more attention. A few examples have been discussed in the text. On the whole, however, synthetic chemists have not exploited these methods. 

Titanium oxide and amorphous Ti02-Si02 did not exhibit any catalytic activity. Neumann et al. [20] reported that amorphous Ti02/Si02 were not active in the epoxidation of olefins, hydroxylation of aromatics and oxidation of alcohols. When sample 10 was... 

Homogeneous catalysis faces a number of obviously trivial but still unresolved problems that depend primarily on mechanistic insight. For example, why do some metal oxides (V2O5, M0O3, CH3Re03) catalyze olefin expoxidation while others (OSO4) catalyze olefin hydroxylation What are the stereoelectronic pre-... 

Hydrogen peroxide-Selenium dioxide. A. Stoll effected olefin hydroxylations with hydrogen peroxide in combination with a stochiometric amount of selenium dioxide in... 

RP ffanzlik, GO Shearer. Secondary isotope effects on olefin hydroxylation by cytochrome P-450. Biochem Pharmacol 27 1441—1444, 1978. 

Achiral polymers synthesized from achiral monomers have been modified after polymerization using asymmetric catalysts to yield optically active polymers. For example, enantioselective ketone reduction, hydrogenation, olefin epoxida-tion, and olefin hydroxylation have been carried on the functional groups of achiral polymers [111, 112]. Such functionalizations, however, are often incomplete or occur with a low degree of asymmetric control. 

The presence of a silica framework with few defects makes TS-1 a highly hydrophobic material suitable for oxidations in the liquid phase with H2O2 as oxidant. Thus, TS-1 has proven to be successful in the oxidation of alcohols, epox-idation of linear olefins, hydroxylation of aromatics, ammoximation of cyclohexanone, oxidation of alkanes to alcohols and ketones, oxidation of amines, oxidation of sulfur-containing compounds, and oxidation of ethers [66-75]. 

Naphthenic adds are a family of carboxylic acid surfactants, primarily consisting of cyclic terpenoids used in source and geochemical charaderisation of petroleum reserves (Brient, Wessner Doyle, 1995). The compwimd group is composed predominately of alkyl-substituted cycloaliphatic carboxyUc adds with smaller amounts of acyclic aliphatic (paraffinic or fatty) acids. Aromatic olefinic, hydroxyl and dibasic adds are also present as minor components of naphthenic adds. The cydoaliphatic adds include single rings and fused multiple rings. 

Some of these oxidations are long-established, for example the use of H2O2/OSO4 for olefin hydroxylation [32]. More recently H2O2 has been used with ruthenium compounds in phase-transfer systems for alcohol... 

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