Other Oxygen-containing Derivatives

Other Oxygen-containing Derivatives. Acetone and furan condense in an acidic medium to form (54). The yield is increased by the addition of metal salts, e.g. IiC104. The increase has been attributed to acidity (pH) effects rather than to effects of metal ion templates. This is the first demonstration of the importance of the effects of pH in metal-assisted cyclizations. Compound (54) is cleaved by m-chloroperoxybenzoic acid to form the novel octaketone (55), with a n s-enedione configuration. The endoperoxide (56) is converted into a bis-epoxide on treatment with catalytic amounts of cobalt(n) 5,10,15,20-tetraphenylporphine at — 10°C, and the epoxide rearranges to (57) at 20 

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Oxygen abstraction reactions from alcohols, ketones, acyl halides and other oxygen-containing compounds by MCI or related derivatives also afforded a route to relatively simple complexes of the oxo halides (Table 24). Thus Nb2Cli0 was found to abstract oxygen from higher ketones to yield, after hydrolysis, alkanes, chloroalkanes or arylalkanes.414... 

Other oxygen-containing systems that have been studied include 2,2,6,6-tetramethyltetrahydropyran-3-one,225 2-alkoxytetrahydropyran-3-ones,226 2-acyl-2,3-dihydro-4W-pyrans,227 cyclic acetals,228 and a wide variety of carbonyl-containing pyranoside derivatives.229... 

Alcohols are at a fairly low oxidation level compared to other oxygen-containing functional groups and consequently are readily prepared by reduction. Large numbers of reductive methods have been reported for the preparation of alcohols. Carboxylic acids and esters react vigorously with lithium aluminum hydride (LAH) to produce primary alcohols. Carboxylic acids, but not esters, are also reduced easily by borane, which is die only reducing agent diat reacts faster widi carboxylic acids dian widi esters or odier acid derivatives. 

Now, let us take a simple functional group such as an OH and substitute it on our carbon atom. The carbinol we now have is capable of yielding only one C-C bond by way of substitution or one unsaturation on our carbon by means of elimination. Alcohols should then be classified under the FN = 1 group. Other oxygen based substituents such as ethers, carboxylic and sulfonic esters, and other heteroatom-containing derivatives such as amines and sulfides behave similarly, as long as we have only one of the heteroatoms substituted on our central carbon. By the same token, alkyl halides, diazonium salts, and even the carbenium ion itself are all capable of giving only one C-C bond with carbon... 

Of the many substrates which have been oxidized in the presence of transition metal complexes, one of the most extensively studied group of compounds has been olefinic hydrocarbons. The obvious incentive for the pursuit of this research is the identification of catalysts which could convert the abundant olefinic hydrocarbons into more valuable oxygen-containing derivatives under mild conditions in high selectivity. Since hydrocarbon-soluble complexes of the transition metals have been successfully applied to the catalytic addition of other small molecules to olefinic substrates, attempts have been made to activate and catalytically transfer dioxygen to olefins in a similar manner. It has been difficult, however, to exclude other pathways by which oxygen can interact with olefins and to achieve selective reactions. In cases where selective oxidations are achieved it is often hard to decide whether products arise via coordination catalysis or autoxidation pathways. 

Monoterpenes, sesquiterpenes, and their oxygen-containing derivatives are an important class of volatile constituents in essential oils of plants that have been found in many types of environmental and geological samples and in other natural or synthetic sources. The identification of terpenes as flavor, fragrance, and curative compounds is important in medicine, veterinary science, and the cosmetics, flavor, and food industries. 

According to this mechanism, one molecule of isocyanate undergoes addition to C=0, and the other addition to C—N. Evidence is that labeling experiments have shown that each molecule of CO2 produced contains one oxygen atom derived... 

Other polymers containing Si in the main chain are the polysilanes. The discovery that polysilane derivatives were radiation sensitive(20), coupled with their stability in an oxygen plasma, has led to a number of microlithographic applications(14, 21-24). For the... 

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