Hydroxyl radicals-mediated oxidative cleavage of the glycosidic bond in cellobiose by copper catalysts and its application to low-temperature depolymerization of cellulose

As the most abundant source of biomass in nature for sustainable production of fuels and chemicals,efficient depolymerization of cellulose under mild conditions,due to the difficulty in selective cleavage of itsβ-1,4-glycosidic bonds,still remains challenging.Here,we report a novel method for oxidative cleavage of the glycosidic bonds by free radicals.Probed by the cellobiose reaction,it was found that·OH radicals,generated from the decomposition of H2O2 catalyzed by CuSO4 or CuO/SiO2,were efficient for selective conversion of cellobiose to glucose and gluconic acid at a low temperature of 333 K,and their selectivities reached 30.0%and 34.6%,respectively,at 23.4%cellobiose conversion.Other radicals,such as·SO4?,also exhibited high efficacy in the cellobiose reaction.Mechanistic studies suggest that the oxidative cleavage of theβ-1,4-glycosidic bond by the free radicals involve formation of the carbon radical intermediate via abstraction of the H atom dominantly at the C1 position.Following this oxidative mechanism,treatment of microcrystalline cellulose with·OH by impregnation with H2O2 and CuSO4 catalyst at 343 K led to significant enhancement in its hydrolysis efficiency.These results demonstrate the effectiveness of this new method in the oxidative cleavage of glycosidic bonds,and its viability for the efficient depolymerization of cellulose at low temperatures,which can be further improved,for example,by exploring new free radicals and optimizing their reactivity and selectivity.

Nonheme Oxovanadium(V,IV) Complexes Catalyze the Oxidative Cleavage of Catechols

It was found that the oxovanadium(V) complex of triethanolamine (TEA) exhibits catalytic activity to the oxidative cleavage of catechols. On the other hand. the vanadyl nitrilotriacetic acid (NTA) complex is inactive. but leads to the formation of stable ternary complex. The main products of the catalytic oxidative cleavage of 3.5-di-tert-butylcatechol were separated and characterized. Based on the results. a reaction mechanism was discussed

Preparation of a ε-caprolactonic diterpenoid derivate by unexpected oxidative cleavage/lactonization of 2-oxoaustroeupatol

From aerial parts of Austroeupatorium inulifolium was isolated the ent-nor-furano triol labdane austroeupatol 1.The compound 1 was treated with IBX showing an unexpected selectivity at the potentially oxidizable sites of the sub-strate yielding the 2-oxoaustroeupatol(2)and 2,19-dioxoaustroeupatol(3).The treatment of 2 with sodium periodate yields a heterocyclic derivative(ε-caprolactone derivate 4)formed by oxidative cleavage and unexpected intramo-lecular attack of the hydroxymethylene(C-19)oxygen to the ketonic carbon(C-2).A plausible mechanistic pathway for the obtention of compound 4 is proposed.

Highly Efficient Oxidative Cleavage of Carbon-Carbon Double Bond over meso-Tetraphenyl Cobalt Porphyrin Catalyst in the Presence of Molecular Oxygen

Highly efficient and selective carbon-carbon double bond aerobic cleavage of olefins catalyzed by metallopor- phyrins was investigated, and carbonyl compounds and epoxide were produced as the main products. CoTPP （co- balt meso-tetraphenyl porphyrin） showed excellent activity for the oxidative cleavage of carbon-carbon double bond by using styrene as model compound, in which the TOF （turnover frequency） and selectivity toward benzaldehyde was obtained with 2×10^4h-1 and 86%,respectively.

Transformations of N-arylpropiolamides to indoline-2,3-diones and acids via C≡C triple bond oxidative cleavage and C(sp^2)–H functionalization

A new palladium-catalyzed oxidative conversion of N-arylpropiolamides and H2O to various indoline-2,3-diones and acids through the C≡C triple bond cleavage and C(sp2)–H functionalization is described,which is promoted by a cooperative action of catalytic CuBr2,2,2,6,6-tetramethyl-1-piperidinyloxy(TEMPO)and O2.The method provides a practical tool for transformations of alkynes by means of a C–H functionalization strategy,which enables the formation of one C–C bond and multiple C–O bonds in a single reaction with high substrates compatibility and excellent functional group tolerance.

1,2-Diethoxyethane catalyzed oxidative cleavage of gem-disubstituted aromatic alkenes to ketones under minimal solvent conditions

Aerobic oxidation using pure dioxygen gas as the oxidant has attracted much attention,but its application in synthetic chemistry has been significantly hampered by the complexity of catalytic system and potential risk of high-energy dioxygen gas.By employing 1,2-diethoxyethane as a catalyst and ambient air as an oxidant,an efficient protocol for the construction of various aryl-alkyl and diaryl ketones through oxidative cleavage of gem-disubstituted aromatic alkenes under minimal solvent conditions has been achieved.

β-Cyclodextrin Promoted Oxidation of Cinnamaldehyde to Natural Benzaldehyde in Water

A facile and efficient procedure has been developed systematically for the oxidative cleavage of cinna-maldehyde to benzaldehyde by sodium hypochlorite with water as the only solvent in the presence of β-cyclodextrin （abbreviated as β-CD）. Different factors influencing cinnamaldehyde oxidation e.g. reaction temperature, the amount of catalyst and oxidant, have been investigated. The yield of benzaldehyde reaches 76% under the optimum conditions （333 K, 4 h, molar ratio of cinnamaldehyde to β-CD is 1：1）. Furthermore, a feasible reaction mecha-nism including the formation of benzaldehyde and the two main byproducts （phenylacetaldehyde and epoxide of cinnamaldehyde） has been proposed.

Studies of the Oxidation of Hexabenzylhexaazaisowurtzitane

A series of oxidation reactions of hexabenzylhexaazaisowurtzitane（HBIW,1） were studied.Compound 1 was treated with potassium permanganate in CH2Cl2 by adding Na2CO3 to adjust pH to 7-8 to obtain tetrabenzoyldibenzylhexaazaisowurtzitane（3） with a yield of 70%.With acetic anhydride（Ac2O） as solvent,monoacetyltribenzoyldibenzylhexaazaisowurtzitane（4）,diacetyldibenzoyldibenzylhexaazaisowurtzitane（5）,triacetylmonobenzoyldibenzylhexaazaisowurtzitane（6） and tetraacetyldibenzylhexaazaisowurtzitane（7） were also obtained from the oxidation of compound 1.The results show that only the oxidative cleavage of the cage system in compound 1 was observed in most cases.The cleavage was a cation catalysis mechanism.

DNA cleavage mediated by water-soluble manganese corrole

The DNA nuclease-like activity of a water soluble manganese corrole 5, 10, 15-tris（N-methyl-4-pyridyl）- corrolatomanga- nese（III） （MnⅢTMPyC） has been investigated. MnⅢMPyC may bind strongly to DNA via outside groove binding mode as indicated by absorption spectra, viscosity measurements and CD spectra. MnInTMPyC exhibited excellent catalytic activity in the DNA oxidative cleavage in the presence of hydroperoxide.

A Concise Total Synthesis of Amphidinin B

A concise total synthesis of amphidinin B, a cytotoxic linear dicarboxylic acid associated with amphidinolide T marine macrolides, has been accomplished from the 19-membered cycloalkene intermediates designed for diverted total synthesis of amphidinolide T1 and T3-T5. The lH and 13C NMR spectra of the synthesized amphidinin B in C6D6 and CDC13 were compared with those for the natural and synthetic forms reported in the literature, showing solvent-dependence of the ^1H and ^13C NMR signals of amphidinin B in C6D6 and CDC13.