Caterina Fusco

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.

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. 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.

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.

Photoreduction of Carbon Dioxide to Formic Acid in Aqueous Suspension: A Comparison between Phthalocyanine/TiO2 and Porphyrin/TiO2 Catalysed Processes

Composite materials prepared by loading polycrystalline TiO2 powders with lipophilic highly branched Cu(II)- and metal-free phthalocyanines or porphyrins, which have been used in the past as photocatalysts for photodegradative processes, have been successfully tested for the efficient photoreduction of carbon dioxide in aqueous suspension affording significant amounts of formic acid. The results indicated that the presence of the sensitizers is beneficial for the photoactivity, confirming the important role of Cu(II) co-ordinated in the middle of the macrocycles. A comparison between Cu(II) phthalocyanines and Cu(II) porphyrins indicated that the Cu(II)- phthalocyanine sensitizer was more efficient in the photoreduction of CO2 to formic acid, probably due to its favorable reduction potential.

On the triggering of free radical reactivity of dimethyldioxirane

Abstract Performing the reaction in the presence of CCl3Br, and/or in inert gas atmosphere, dramatically changes the reaction kinetics, rate-law and product distribution of adamantane oxyfunctionalization by dimethyldioxirane (1a). The kinetics of decomposition of the dioxirane is also markedly influenced by the addition of CCl3Br and by depletion of O2 gas. The data suggest that these conditions can trigger dioxirane radical reactions; these are widely different from the straightforward, highly selective concerted O-insertion into CH bonds which would take place in the absence of CCl3Br and of conditions inducing radical reactivity.

Oxidation of catechol and of 2,6-di-tert-butylphenol by dioxiranes

In a biomimetic transformation, the selective oxidation of catechol (2) to Z,Z-muconic acid (3) has been achieved under extremely mild conditions using methyl(trifluoromethyl)dioxirane (1b). Both dioxirane 1b and dimethyldioxirane (1a) have been applied to the oxidation of 2,6-di-tert-butylphenol (4); the product natures suggest the incursion of radical pathways.

Selective oxidation of O-isopropylidene derivatives of diols to 2-hydroxy ketones employing dioxiranes☆

Employing dimethyldioxirane (1a) or methyl(trifluoromethyl)dioxirane (1b), the direct conversion of O-isopropylidene derivatives of 1,2-diols into the corresponding 2-hydroxy ketones can be achieved in high yield and under mild conditions; optically active acetonides are transformed into homochiral 2-hydroxy ketones in high optical yield, and with preservation of configuration at the C∗OH chiral center proximal to that undergoing oxidation to carbonyl. The diacetonide of 1,4-Diphenylbutan-1,2:3,4-tetraol could be selectively converted into 1,4-diphenyl-1-oxo-2-hydroxy 3,4-acetonide, with removal of just one acetonide moiety.

Selective Hydroxylation of Methane by Dioxiranes under Mild Conditions

The direct conversion of methane to methanol at low temperatures was achieved selectively using dioxiranes 1a,b either in the isolated form or generated in situ from aqueous potassium caroate and the parent ketone at a pH close to neutrality. Results suggest that the more powerful dioxirane TFDO (1b) should be the oxidant of choice.