Ruggero Curci

Oxidation of organic sulphides—XV : Steric effects on the alkaline oxidation of sulphoxides to sulphones

Abstract The oxidation of highly branched penyl-alkyl and di-alkyl sulphoxides shows that in the alkaline oxidation steric hindrance has a more pronounced influence than in acidic oxidation, even if the steric effects are not very large. On the basis of these and previous results some suggestions on the geometry of the transition state of the alkaline oxidation are advanced.

Oxidations by methyl(trifluoromethyl)dioxirane. 3. Selective polyoxyfunctionalization of adamantane

Adamantane (1) can be converted directly into adamantan-1,3,5-triol (5) and into adamantan-1,3,5,7-tetraol (6) under remarkably mild conditions by employing an excess of isolated methyl(trifluoromethyl)dioxirane (3a) in solution. This new dioxirane species was found to be over 7,000-fold more reactive than dimethyldioxirane (3b) in performing adamantane hydroxylations.

Enantioselective epoxidation of unfunctionalized alkenes using dioxiranes generated in situ

Abstract Using (+)-3-(trifluoroacetyl)camphor, or R (+)- and S (−)-3-methoxy-3-phenyl-4,4,4-trifluoro-butan-2-one as precursors for chiral dioxiranes generated in situ , the asymmetric epoxidation of prochiral alkenes trans - β -methylstyrene, trans -2-octene, and cis -2-methyl-7-octadecene has been achieved in 12–20% ee.

Oxidation of acetals, an orthoester, and ethers by dioxiranes through α-CH insertion

Abstract Dimethyldioxirane ( 1a ) and methyl(trifluoromethyl)dioxirane ( 1b ) efficiently afford cleavage of acetals and of ketals to carbonyl products under mild, neutral conditions. Dialkyl ethers are cleaved to alcohols, aldehydes and/or carboxylic acids, whereas reaction of dioxiranes 1a, b with medium-ring cyclic ethers transforms the latter into lactones, via the corresponding hemiacetals, with no appreciable formation of ring-opened products. The products can be accounted for on grounds of a remarkably selective O -atom insertion by the dioxirane into C-H bonds α to the ether functionality.

Oxidation of alkynes by dioxiranes

Abstract In situ generated or isolated dimethyldioxirane (1a) and methyl(trifluoromethyl)dioxirane (1b) efficiently afford oxidation of alkynes, most likely via oxirene intermediates, which rearrange into ketene or α,γ-unsaturated carbonyls, or else are further oxidized to α,β-dicarbonyls. Diphenylacetylene and phenylacetylene yield mostly ketene derived products, whereas 8-hexadecyne (an internal dialkyl alkyne) gives 9-hexadecen-8-one (both trans and cis) as the main product. Reaction of cyclodecyne (a conformationally rigid cycloalkyne) with isolated 1b affords cis-bicyclo[5.3.0]decan-2-one (15) and cis-bicyclo[4.4.0]decan-2-one (16), which derive from the oxirene by stereoselective 1.5- and 1,6-transanular insertion, respectively.

Oxidations by methyl trifluoromethyl dioxirane. Epoxidation of enol ethers

Abstract Isolated methyl trifluoromethyl dioxirane 4b has been employed to achieve the rapid, low temperature epoxidation of enol ethers, such as alkoxy(aryl)methylidene adamantanes 1a–e and methoxy(2-naphthyl)methylidene 2-bornane 1f , affording the corresponding spirooxiranes in excellent (92–97%) yields.

Evidence concerning peroxovanadate structures in solution and their role in catalytic oxidation process

Abstract Evidence concerning the nature of peroxometal intermediates in the oxidation of organic substrates by hydrogen peroxide or t-butyl hydroperoxide by vanadium(V) compounds is critically reviewed; it suggests formation of either metal μ-peroxoester (or peroxoacid) 2 or side-bonded peroxometal intermediates 3. Kinetic and spectroscopic data, as well as comparison with analogous systems, indicate that an entirely different situation arises in the interaction of alkyl hydroperoxides or hydrogen peroxide with the metal center, in that while alkyl hydroperoxides generate metal μ-peroxoester intermediates, H 2 O 2 produces vanadium(V)—side-bonded peroxocomplexes. It is suggested that formation constant ( K t ) values of the peroxometal species and kinetic behaviour in catalytic oxidation permit distinction between these two significantly different modes of binding of the peroxide to the metal.

Oxidations by methyl(trifluoromethyl)dioxirane. 4.1 oxyfunctionalization of aromatic hydrocarbons

Abstract By using the title dioxirane ( 1a ), naphthalene ( 2 ), phenanthrene ( 3 ), and anthracene ( 4 ) have been converted into anti -naphthalene-1,2;3,4-dioxide ( 2′ ), phenonthrene-9,10-oxide ( 3′ ), and anthraquinone ( 4′ ), respectively, in high yield and under mild conditions. However, the transformation of pyrene ( 5 ) - an higher homologue of the polycyclic aromatic hydrocarbon series - into the corresponding arene oxide was found to procced much less effectively.

Fenton Type Activation and Chemistry of Hydroxyl Radical

Nowhere among the multitude of organic compounds is the need for peroxide activation more apparent than among the simple compounds of C, H and O: hydrocarbons, carboxylic acids, alcohols and ethers. In these molecules there are no nucleophilic sites or other types of centers that can react under mild conditions with hydrogen peroxide HOOH. This is well illustrated by the case of polycarboxylic acids which Fenton [1] in 1894 was trying to oxidize with HOOH when he found the strong promotion by ferrous ion.

Selective oxidation of tertiary-secondary vic-diols to α-hydroxy ketones by dioxiranes

Abstract Isolated dimethyldioxirane ( 1a ) and methyl(trifluoromethyl)dioxirane ( 1b ) efficiently afford the conversion of bicyclic diols bicyclo [2.2.2]octane-1,2-diol ( 2 ) and (+)-pinane-2,3-diol ( 6 ), of tricyclic diols adamantane-1,2-diol ( 3 ), homoadamantane-3,4-diol ( 4 ), and of homopentaprismane-3,4-diol ( 5 ) into the corresponding α-hydroxy ketones in high yields and under mild conditions. In the oxidation of (+)-pinane-2,3-diol ( 6 ), (−)-2-hydroxy-3-pinanone ( 11 ) is obtained in optical yield > 97% with retention of configuration.