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Supercritical carbon dioxide (scCO2) is an effective reaction medium to perform the oxidation of primary and secondary aliphatic alcohols to the corresponding carbonyl compounds with chromium trioxide supported on silica. These reactions are performed by flowing a solution of the alcohol in scCO2 through a column containing the supported reagent and recovering the product by depressurization.

Potassium peroxomonosulfate deposited onto silica SiO(sub 2).KHSO(sub 5) efficiently reacts with ketones in dichloromethane at room temperature to give the corresponding esters or lactones in quantitative yields. This method avoids hydrolysis of the reaction products and the Baeyer-Villiger reaction is catalyzed by potassium hydrogensulfate present in the supported reagent.

The mechanism of the oxygenation of alkane C-H bonds with methyl(trifluoramethyl)dioxirane is studied through the effect of the substituent and solvent on the rate of oxygenation of 2-substituted adamantanes. The results suggest a remarkable electron deficiency at the reacting carbon atom in the transition state leading to the regular oxygenation products.

The detailed study of the oxidation thianthrene 5-oxide with methyl(trifluoromethyl)dioxirane in different solvents and in the presence of (super 18)O isotopic tracers is reported. The flexibility of the thianthrene 5-oxide molecule in solution allows for transannular interaction of the sulfoxide group with the expected zwetterionic and hypervalent 10-S-4 sulfurane intermediates formed in the oxidation and biases the course of the reaction toward the monooxygenation pathway.

Palladium-catalyzed cross-coupling reactions of racemic alpha-bromo sulfoxides with boronic acids are done in either aqueous or nonaqueous medium. The homocoupling side reaction is favored by the use of aqueous base and the presence of oxygen.

A systematic and general study on the mechanism of simple sulfides with dimethyldioxirane (DMDO) and methyl (trifluoromethyl) dioxirane (TFDO), which provides clear evidence for the involvement of hypervalent sulfur species in the oxidation process, is described. The mechanism involves an initial electrophilic attack of the dioxirane to the sulfur atom to give a zwitterionic species which in a reversible cyclization step gives rise to the 10 S-4 hypervalent sulfur adduct.

The equatorial/axial selectivity in monooxygenation of methylene C-H bonds of cyclohexanes was studied to determine the influence of remote substituents.

Research has been conducted on the a series of isomeric carboxylic acid and unsaturated lactones. The protonation of these acid and lactones in the sulfuric and trifluoromethanesulfonic acids has been carried out and the results are discussed.

A comparative study was conducted to investigate the reactivity of primary and quaternary allylic and homoallylic alkenylammonium salts with dimethyldioxirane and m-chloroperbenzoic acid. The study determined the stereochemical outcome of the epoxidation of the cyclic quaternary allylic salt (2-cyclohexenyl)trimethylammonium p-chlorobenzenesulfonate with dimethyldioxirane and m-chloroperbenzoic acid. It also determined the epoxidation rate constants for the reaction of select allylic and homoallylic primary and quaternary ammonium salts.

A study was conducted to analyze the influence of solvents, temperature, lithium salts and acidity of the proton source on enantioselective protonation with alpha-sulfinyl alcohols. The alcohols were determined with high and moderate diastereoselectivity by minimizing corresponding ketones. Results indicated that the presence of lithium bromide in the enolization step supported good stereoselectivity resulting from the effects of excess lithium cation on the structure of the enolate.

The protonation of epoxy compounds with arenesulfonic acids is a suitable procedure for synthesizing epoxyalkylamines and protecting primary and secondary alkenylamines from N-oxidation by electrophilic epoxidation. Dimethyldioxirane, m-CPBA and methyl(trifluoromethyl) dioxirane causes the epoxidation of the primary and secondary alkenylammonium arenesulfonates. The epoxidation is marked by high directing effect from ammonium group.

N oxidation of secondary C-H and aliphatic tertiary bonds in the alkyl side chain was possible by employing methyl(trifluoromethyl)-dioxirane (1b) ketone-free solution in methylene chloride at zero degrees centigrade. This oxidation is not possible in primary, secondary and tertiary alkylamines having tetrafluoroborate salts. Intramolecular condensation of amino ketones 5f-h yielded 2,3,4,5-tetrahydro-6-alkylpyridines when the secondary C-H bonds contained in the linear aliphatic primary amines underwent oxidation at the epsilon position.

The protonation and thermolytic reactions of nine isomeric carboxylic acids and lactones, C5H8O2, in highly acidic medium provide empirical support for the assignment of their corresponding gas-phase structures. Except for 4-pentenoic acid, all the cations isomerize eventually into protonated gamma-valerolactone and finally into protonated cyclopentenone. Their chemical ionization mass spectra show a close correlation between their solution and gas-phase behavior, thereby allowing reasonable assignment of their gas-phase ion structures based on their solution chemistry.

A study was done on the effects of tetrabutylammonium iodide or lithium iodide on dioxirane. It was shown that catalytic amounts of tetrabutylammonium iodide or lithium iodide promote the conversion of dioxirane into trifluoroacetone and dioxygen. In addition, it was suggested that a one-electron-transfer chain reaction accounts for the observed electron-transfer chemistry between dioxirane and the iodide ion.

The behavior of methyl(trifluoromethyl)dioxirane (TFDO) as a reagent in the oxidation of the lineal, cyclic and bicyclic aliphatic p-chlorobenzoic and p-chlorobenzenesulfonic acid esters was investigated. The resulting products, keto and hydroxy esters, indicated that regioselective oxidation took place at distant positions in the hydrocarbon chain. This suggests that esterification is a suitable method for protecting aliphatic alcohols during oxidation due to the electron-withdrawing nature of the ester group.

The synthesis of iodinated aromatic compounds using aromatic substrates with IPy2BF4 was studied. Acceptable yields of iodobenzene were obtained with a 1:2 molar ratio of IPy2-BF4/HBF4, with improved yield when an excess of IPy2BF4 was added. Gradual addition of IPy2BF4 to the CH2Cl2 solution also resulted in increased yields. There were no significant differences between the acids used in relation to polyalkylbenzene iodination. Rapid formation of 4-iodanisole was achieved using either acid.

Methyl(trifluoromethyl)dioxirane is more efficient than the dimethyl species in the regiospecific and stereoselective oxidation of (R)-(-)-2-phenylbutane into (S)-(-)-2-phenyl-2-butanol. The choiceof solvent has little effect on the transition state ordering but less activation energy is needed in the ketone-free methylene chloride solution thanin 1,1,1-trifluoropropanone. Retention of configuration and the large entropy values suggest a mechanism involving an ordered transition state I, with significant diradical character owing to the weak peroxide bond.

The stereoselectivity-determining oxidative addition step in the Suzuki-Miyaura cross-coupling of [alpha]-bromo sulfoxides is studied by using density functional theory (DFT) calculations on model system defined Pd[(P[Me.sub.3]).sub.2] and C[H.sub.3]SOC[H.sub.2]Br. The lowest energy transition states have corresponded to nucleophilic substitution mechanisms and the energy-lowering and stereodirecting role of the sulfinyl substituent is explained by its interactions with the palladium center.

The successive addition of 2 equiv of vinylmagnesium bromide to squarates is used for studying the elements controlling the regio- and stereoselectivity of additions to substituted [alpha],[beta]-unsaturated ketones. The results showed that complex induced proximity effect (CIPE) influenced both the kinetics and the thermodynamics of the vinylmagnesium addition, leading to lowered barrier for the 1,4-addition when compared to 1,2-addition and increased stability of the 1,4-product.

1,1,1-Trifluoroacetone has reacted as a hydride-acceptor in the Oppenauer oxidation of secondary alcohols in the presence of diethylethoxyaluminum. The oxidant has allowed for the selective oxidation of secondary alcohols in the presence of primary alcohols.

Supercritical carbon dioxide (scC[O.sub.2]) is an efficient reaction medium to perform the Baeyer-Villiger oxidation with hydrated silica-supported potassium peroxomonosulfate (h-Si[O.sub.2].KHS[O.sub.5]) under flow-through conditions. The reaction in scC[O.sub.2] is found to be more efficient than in n-hexane under similar conditions, which is attributed to better transport and solvating properties of the supercritical medium with regard to n-hexane.

The apparent dipole moment and low temperature (super 1)H NMR measurements of thianthrene-5-oxide in different solvents is reported. The results provide evidence for the conformational mobility of thianthrene-5-oxide in solution, and that the relative populations of pseudoequatorial and pseudoaxial conformers are solvent- and temperature-dependent.

The C‐C ring closure of α‐chloromethyl alkyl or aryl N‐aryl imines catalyzed with 1 to 10 % Pd(OAc)2/P(p‐tolyl)3 afford efficiently 2‐aryl‐ and 2‐alkyl‐1H‐indoles. The heterocyclization reaction involves the initial formation of [2‐(arylimino)ethyl]palladium(II) chloride complexes with subsequent C‐H activation of the aromatic amine ring. Readily or commercially available α‐chloromethyl‐aryl or ‐alkyl ketones are used as the precursors. Functionalized indoles at the benzene ring are obtained when the imines are derived from substituted anilines. Palladium‐catalyzed heterocyclization of α‐chloromethyl alkyl or aryl N‐aryl imines gives efficiently 2‐aryl‐ and 2‐alkyl‐1H‐indoles. Readily or commercially available α‐chloromethyl‐aryl or ‐alkyl ketones are used as the precursors. Indoles containing substituents, including halogens, at the benzene ring are also easily accessible simply by use of the appropriate substituted aromatic amine. [ABSTRACT FROM AUTHOR]