Aqueous phase C-H bond oxidation reaction of arylalkanes catalyzed by a water-soluble cationic Ru(III) complex [(pymox-Me2)2RuCl2]+BF4-

Visible-light photocatalytic selective oxidation of C(sp3)–H bonds by anion–cation dual-metal-site nanoscale localized carbon nitride

Anion–cation dual-metal-site nanoscale localized carbon nitride exhibits a significantly enhanced photocatalytic activity for the oxidation of alkanes and alcohols with a high activity and a wide functional group tolerance.

Site-selective unidirectional benzylic sp3 C–H oxidation of dodecahydrotriphenylene with RuCl3–NaIO4: formation of benzylic ketones

Dodecahydrotriphenylene, a higher homologue of trindane chemoselectively undergoes unidirectional benzylic sp³ C–H oxidation and the central benzene ring remains intact unlike that in trindane under similar reaction conditions. RuO₄ which generally attacks sp² C–H to form oxidative products is found to give benzylic ketones via sp³ C–H oxidation. Density functional theory (DFT) calculations have also been performed to analyse the potential energy, energy barrier and HOMO–LUMO energy gap of the products.

Dodecahydrotriphenylene, a higher homologue of trindane chemoselectively undergoes unidirectional benzylic sp³ C–H oxidation and the central benzene ring remains intact unlike that in trindane under similar reaction conditions.

Lemon juice catalyzed C-C bond formation via C-H activation of methylarene: a sustainable synthesis of chromenopyrimidines

An economical and proficient approach has been developed for the synthesis of chromenopyrimidines via three-component reaction of thiobarbituric acid/barbituric acid, methylarenes and dimedone/1,3-cyclohexanedione by using lemon juice as a natural, biodegradable catalyst and TBHP as an oxidant. This transformation involves metal-free C-C bond formation via C-H activation of methylarenes under mild reaction conditions.

Selective benzylic C-H monooxygenation mediated by iodine oxides

A method for the selective monooxdiation of secondary benzylic C–H bonds is described using an N-oxyl catalyst and a hypervalent iodine species as a terminal oxidant. Combinations of ammonium iodate and catalytic N-hydroxyphthalimide (NHPI) were shown to be effective in the selective oxidation of n-butylbenzene directly to 1-phenylbutyl acetate in high yield (86%). This method shows moderate substrate tolerance in the oxygenation of substrates containing secondary benzylic C–H bonds, yielding the corresponding benzylic acetates in good to moderate yield. Tertiary benzylic C–H bonds were shown to be unreactive under similar conditions, despite the weaker C–H bond. A preliminary mechanistic analysis suggests that this NHPI-iodate system is functioning by a radical-based mechanism where iodine generated in situ captures formed benzylic radicals. The benzylic iodide intermediate then solvolyzes to yield the product ester.

Hydrogen peroxide as a hydride donor and reductant under biologically relevant conditions

Some ruthenium-hydride complexes react with O2 to yield H2O2, therefore the principle of microscopic reversibility dictates that the reverse reaction is also possible, that H2O2 could transfer an H- to a Ru complex. Mechanistic evidence is presented, using the Ru-catalyzed ABTS˙- reduction reaction as a probe, which suggests that a Ru-H intermediate is formed via deinsertion of O2 from H2O2 following coordination to Ru. This demonstration that H2O2 can function as an H- donor and reductant under biologically-relevant conditions provides the proof-of-concept that H2O2 may function as a reductant in living systems, ranging from metalloenzyme-catalyzed reactions to cellular redox homeostasis, and that H2O2 may be viable as an environmentally-friendly reductant and H- source in green catalysis.

N-Doped carbon nanofibers derived from bacterial cellulose as an excellent metal-free catalyst for selective oxidation of arylalkanes

N-Doped carbon nanofibers derived from one-step pyrolysis of low-cost bacterial cellulose with the assistance of urea were an excellent metal-free carbocatalyst for selective oxidation of arylalkanes.

Cobalt(ii)-catalyzed benzylic oxidations with potassium persulfate in TFA/TFAA

A cobalt-catalyzed C(sp³)–H oxygenation reaction to furnish aldehyde was herein reported. This transformation demonstrated high chemo-selectivity, and tolerated various methylarenes bearing electron-withdrawing substituents. This reaction provided rapid access to diverse aldehydes form methylarenes. Notably, TFA/TFAA was used for the first time as a mixed solvent in cobalt-catalyzed oxygenation of benzylic methylenes.

A Co-catalyzed C(sp³)–H oxygenation reaction to furnish diverse aldehydes from methylarenes in TFA/TFAA is reported. This transformation demonstrated high chemo-selectivity, and tolerated with various methylarenes bearing electron-withdrawing substituents.

TBHP-promoted direct oxidation reaction of benzylic Csp3–H bonds to ketones

A metal-free oxidation system employingtert-butyl hydroperoxide (TBHP) has been developed for selective oxidation of structurally diverse benzylic sp³C–H bonds.

Chelating bis-N-heterocyclic carbene complexes of iron(ii) containing bipyridyl ligands as catalyst precursors for oxidation of alcohols

Chelating bis-N-heterocyclic carbene (bis-NHC) complexes of iron(ii) containing pyridyl ligands have been prepared by the reaction of [FeCl2L] [L = bipy (1), phen (2)] with [LiN(SiMe3)2] and a bis(imidazolium) salt. The [Fe(bis-NHC)L(I)2] complexes were active pre-catalysts in the oxidation of 1-phenylethanol with tert-butyl hydroperoxide in neat conditions, affording a quantitative yield of acetophenone in 4.5 h. The catalyst could be reused up to six cycles giving a turnover number (TON) of 1500. Various secondary alcohols, both aromatic and aliphatic were selectivity oxidised to the corresponding ketones in excellent yields. Compound 1 is stable in acetonitrile solution for ca. 4 h, although after 16 h, it evolves to a mixture of [Fe(bis-NHC)(bipy)2]I2 (3), [Fe(bipy)3](2+) and bis-imidazolium salt. The molecular structure of 3 has been determined by X-ray diffraction studies.

Benzylic C(sp(3))-H Functionalization for C-N and C-O Bond Formation via Visible Light Photoredox Catalysis

A visible light mediated highly selective benzylic C-H bond functionalization for intermolecular C-N and C-O bond formation is reported. This cross-dehydrogenative coupling reaction demonstrates a straightforward protocol for incorporating the heteroaromatics to the benzylic position. Benzylic oxidation of various alkyl aryls to corresponding carbonyl compounds has also been reported.

Cu-Catalyzed selective cascade sp(3) C-H bond oxidative functionalization towards isoxazoline derivatives

The first Cu-catalyzed cascade sp(3) C-H bond oxidative functionalization of the 2-ethylazaarenes has been developed. The two different sp(3) C-H bonds in 2-ethylazaarenes are selectively oxidized and four new types of bonds (C=O, C=N, C-C, C-O) are constructed in one operation. Starting from the simple substrates and cheap nitro source, this reaction provides an efficient approach to produce new kinds of isoxazolines.

Cu-catalyzed sp3 C–H bond oxidative functionalization of alkylazaarenes and substituted ethanones: an efficient approach to isoxazoline derivatives

Cu-catalyzed sp³ C–H bond oxidative functionalization of alkylazaarenes and substituted ethanones to different kinds of isoxazoline derivatives by 1,3-dipolar cycloaddition is reported.

Synthesis of fluorenones by using Pd(ii)/Mg–La mixed oxide catalyst

Palladium(ii)/magnesium–lanthanum mixed oxide (Pd(ii)/Mg–La mixed oxide) catalyst was used in the dehydrogenative cyclization of benzophenones to afford fluorenones.

Allylic and benzylic sp3 C–H oxidation in water

A copper-catalyzed method for the oxidation of allylic and benzylic sp³ C–H by aqueous tert-butyl hydroperoxide (T-Hydro) in water using a recyclable fluorous ligand has been developed.

Catalytic oxygenation of sp3 “C–H” bonds with Ir(iii) complexes of chelating triazoles and mesoionic carbenes

Ir(iii) complexes with chelating triazole and mesoionic carbene ligands are potent pre-catalysts for the direct oxygenation of C–H bonds.