Presence Of t-BuOOH Research Articles

Formation of the mutagenic DNA lesion 1,N2-ethenoguanine induced by heated cooking oil and identification of causative agents

BackgroundThe DNA-damaging compounds in heated cooking oil were identified as guanosine adducts. Heated vegetable oil was subjected to deep-frying conditions at 170 °C for 45 min, reacted with isopropylidene guanosine (ipG) at pH 7.4, and the resulting compounds were separated by high-performance liquid chromatography (HPLC).ResultsTwo adducts, 8-hydroxy-ipG and 1,N2-etheno-ipG, were identified in the reaction mixture. One of the major components in heated cooking oil, 2,4-heptadienal (HDE), efficiently produced etheno-ipG from ipG in the presence of tBuOOH. An oxidized HDE solution was fractionated using HPLC to identify causative agents, and each fraction was tested for etheno-ipG formation. In addition to the known lipid peroxidation product, 4,5-epoxy-2-heptenal, two unknown polar components with potent etheno-ipG formation activity were discovered. Based on Mass and UV spectra, their structures were identified as 6-oxo- and 6-hydroxy-2,4-HDE. Similarly, 6-oxo- and 6-hydroxy-2,4- decadienal (DDE) were formed from 2,4-DDE. Significant amounts of 6-oxo- and 6-hydroxy-2,4-alkadienal were detected in the heated cooking oil. These compounds induced the formation of 1,N2-ethenoguanine in nucleosides and DNA, especially in the presence of tBuOOH. Moreover, the formation of 6-oxo- and 6-OH-HDE from 2,4-HDE was accelerated in the presence of hemin and tBuOOH.ConclusionThe results suggest that these compounds are not only generated during the oil heating process but also produced from 2,4-alkadienal through digestion under normal physiological conditions, especially after ingesting heme- and alkyl-OOH-containing diets. Moreover, these compounds can be formed within cells under oxidative stress, potentially linking them to gastrointestinal carcinogenesis.

Catalytic oxidation of biomass-derived 5-hydroxymethylfurfural to 5-hydroxymethyl-2-furancarboxylic acid by Co-based MOFs

The selective oxidation of 5-hydroxymethylfurfural (HMF) to 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) has been investigated on Co-based MOF catalysts. ZIF-67 (ZIF, Zeolitic Imidazolate Framework), Co-BTC and Co-BTC-2mim were solvothermally synthesized by the association of cobalt with 2-methylimidazole (2-mim), 1,3,5-benzenetricarboxylic acid (H3BTC), or a mixture of the two linkers. Besides these, a novel core-shell Co3O4 @Co-BTC structure with a core of Co3O4 and Co-BTC on its outer layer has also been synthesized by a simple replacement of the cobalt nitrate precursor with Co3O4. Among the prepared materials the core-shell Co3O4 @Co-BTC catalyst afforded the proper catalytic features (i.e., specific density of the acid and base site combined with the high accessibility of the HMF molecules to the active Co sites) for a high selectivity to HMFCA (89%) at a HMF conversion (XHMF) of 79%, at 60 ℃ and after only 1 h, in the presence of t-BuOOH as oxidant and acetonitrile as solvent.

Enantioselective Radical-Type 1,2-Alkoxy-Phosphinoylation to Styrenes Catalyzed by Chiral Vanadyl Complexes.

A series of vanadyl complexes bearing 3-t-butyl-5-bromo, 3-aryl-5-bromo, 3,5-dihalo-, and benzo-fused N-salicylidene-tert-leucinates was examined as catalysts for 1,2-alkoxy-phosphinoylation of 4-, 3-, 3,4-, and 3,5-substituted styrene derivatives (including Me/t-Bu, Ph, OR, Cl/Br, OAc, NO2 , C(O)Me, CO2 Me, CN, and benzo-fused) with HP(O)Ph2 in the presence of t-BuOOH (TBHP) in a given alcohol or cosolvent with MeOH. The best scenario involved the use of 5 mol % 3-(2,5-dimethylphenyl)-5-Br (i.e., 3-DMP-5-Br) catalyst at 0 °C in MeOH. The desired catalytic cross coupling reactions proceeded smoothly with enantioselectivities of up to 95 % ee of (R)-configuration as confirmed by X-ray crystallographic analysis of several recrystallized products. The origin of enantiocontrol and homolytic substitution of the benzylic intermediates by vanadyl-bound methoxide and radical type catalytic mechanism were proposed.

Manganese(III) complexes stabilized with N-heterocyclic carbene ligands for alcohol oxidation catalysis.

The chemistry of N-heterocyclic carbenes with Earth-abundant manganese has largely focused on low-valent systems for reductive catalysis. Here, we have decorated imidazole- and triazole-derived carbenes with phenol substituents to access higher-valent Mn(III) complexes [Mn(O,C,O)(acac)], where acac = acetylacetonato, and O,C,O = bis(phenolate)imidazolylidene (1) or bis(phenolate)triazolylidene (2). Both complexes catalyze the oxidation of alcohols in the presence of tBuOOH as terminal oxidant. Complex 2 is slightly more active than 1 (TOF up to 540 h-1vs. 500 h-1), yet significantly more robust towards deactivation. Secondary and primary alcohols are oxidized, the latter with high selectivity and essentially no overoxidation of the aldehyde product to carboxylic acids unless the reaction time is substantially extended. Mechanistic investigations using Hammett parameters, IR spectroscopy, isotope labelling experiments, and specific substrates and oxidants as probes support the formation of a manganese(V) oxo system as the active species and subsequent turnover-limiting hydrogen atom abstraction.

Post-functionalization of dibenzothiophene to functionalized biphenyls via a photoinduced thia-Baeyer-Villiger oxidation

The Baeyer-Villiger reaction is used extensively in organic chemistry. Sila- and bora-variants have also been documented widely, with these processes underpinning, for example, the Fleming-Tamao oxidation and hydroborative alkene hydration, respectively. By contrast, the development of thia-Baeyer-Villiger reactions involving sulfoxides has long been considered unlikely because competitive oxidation to the sulfone occurs exclusively. Here, we disclose a photoinduced thia-Baeyer-Villiger-type oxidations; specifically, we find that exposure of dibenzothiophene (DBT) derivatives to an iron porphyrin catalyst under Ultraviolet irradiation in the presence of t-BuOOH generates sulfinic esters in up to 87% yield. The produced sulfinic esters are transformed to a variety of biphenyl substrates including biphenyl sulfoxides, sulfones and sulfonamides in 1-2 steps. These results provide a mild process for the selective functionalization of sulfur compounds, and offer a biomimetic approach to convert DBT into 2-hydroxybiphenyl under controllable stepwise pathway. Based upon experimental evidences and DFT calculation, a mechanism is proposed.

Kinetics and localisation of haemin-induced lipoprotein oxidation

Haemin (iron (III)-protoporphyrin IX) is a degradation product of haemoglobin in circulating erythrocytes. Haemin may play a key oxidising agent for lipoprotein oxidation in patients with haemolytic anaemia. In this study, kinetic changes in chemical composition and target sites of haemin-induced LDL and HDL oxidation were investigated. Haemin initially induced the loss of α-tocopherol, followed by accumulation of lipid hydroperoxide (LP) and alteration of core lipid fluidity. The absence of LP in HDL was explained by the antioxidant activity of PON in addition to α-tocopherol. The target site of haemin was evaluated by ESR spin labelling with 5- and 16-doxyl steric acids. In the presence of t-BuOOH and haemin, ESR signal decay of the doxyl moiety demonstrated the initiation phase and the propagation phase of lipid peroxidation. The results of the lag time and the rate of signal decay indicated that haemin is located near the 16th carbon atom of the fatty acid chain in the phospholipid layer. The analyses of motion parameters, order parameter (S) of 5-DS and rotational correlation time (τ) of 16-DS, supported the observation that the lipid properties changed near the hydrophobic region rather than at the surface region of lipoproteins. Moreover, ESR spin labelling demonstrated that haemin molecules but not iron ions caused lipoprotein oxidation. In conclusion, haemin is a potent inducer of lipoprotein oxidation, and the target site for this oxidation is near the hydrophobic core of the lipoprotein leading to the loss of antioxidant activities and changes in lipid composition and physical properties.

Copper-catalyzed α-benzylation of BODIPYs via radical-triggered oxidative cross-coupling of two C-H bonds.

An oxidative cross-dehydrogenative coupling of BODIPYs with toluene and its derivatives has been developed, allowing for the facile synthesis of a broad range of structurally diverse α-benzylated BODIPYs. The method exhibits excellent chemoselectivity, affording exclusively α-benzylated BODIPYs in the presence of t-BuOOH and a catalytic amount of Cu(OAc)2. The direct use of readily available toluene and its derivatives as coupling partners avoids unproductive steps for preactivating the functional group installation, and is therefore attractive. Most of the resulting dyes are highly emissive in the solid state due to the introduction of bulky benzyl groups onto the BODIPY core.

Synergistic Catalysis: Pd(II) Catalyzed Oxidation of 1,4-Dihydroquinones in the Pd(II) Catalyzed 1,4-Oxidation of Cyclic 1,3-Dienes

Palladium(II) carboxylate salts have been shown to catalyze the oxidation of various hydroquinones to benzoquinones in the presence of t-BuOOH. This new catalytic system has been integrated into the oxidative 1,4-functionalization of cyclic 1,3-dienes where the palladium plays a remarkable dual role, catalyzing both the diene oxidation itself and the regeneration of the active quinone oxidant, which is required for diene functionalization. These new conditions offer considerable increases in reaction rate over prior art and allow a significant decrease in the equivalents of the nucleophilic carboxylate required for full conversion.

ChemInform Abstract: Directing‐Group‐Assisted Copper‐Catalyzed Oxidative Esterification of Phenols with Aldehydes.

AbstractA novel, green, and ligand‐free approach is developed for the direct synthesis of esters, utilizing the copper‐catalyzed oxidative esterification of phenols with aldehydes in the presence of tBuOOH as an oxidant.

ChemInform Abstract: Efficient 2‐Sulfolmethyl Quinoline Formation from 2‐Methylquinolines and Sodium Sulfinates under Transition‐Metal Free Conditions.

AbstractA series of 2‐sulfonylmethyl quinolines (III) and (V) is readily prepared by a sulfonylation of corresponding 2‐methylquinolines with sodium sulfinates in the presence of tBuOOH and KI.

ChemInform Abstract: Synthesis of Functionalized Carbamates and Quinones via Sequential Oxidation of Salicylaldehydes Using TBHP as the Oxidant.

AbstractThe oxidative amidation of salicylaldehydes with cyclic amines in the presence of tBuOOH gives a wide variety of salicylamides.

ChemInform Abstract: Co‐Catalyzed Synthesis of 1,4‐Dicarbonyl Compounds Using TBHP Oxidant.

AbstractCobalt catalyzed coupling of styrenes with a variety of activated organic bromides such as α‐bromoesters, α‐bromoamides, and α‐bromoketones is studied in the presence of tBuOOH as the oxidant.

ChemInform Abstract: Four Tandem C—H Activations: A Sequential C—C and C—O Bond Making via a Pd‐Catalyzed Cross Dehydrogenative Coupling (CDC) Approach.

AbstractTreatment of activated benzenes with methylarenes in the presence of tBuOOH and Pd(OAc)2 is found to provide a new, unprecedented method to prepare ortho‐functionalized diaryl ketones.

ChemInform Abstract: Direct Carbo‐Acylation Reactions of 2‐Arylpyridines with α‐Diketones via Pd‐Catalyzed C—H Activation and Selective C(sp2)—C(sp2) Cleavage.

AbstractIn the presence of tBuOOH, 2‐arylpyridines (I) as well as benzoquinoline (IX) react with symmetric or asymmetric diketones to give the corresponding acylated products.

ChemInform Abstract: Enantioselective Oxidative Cross‐Dehydrogenative Coupling of Tertiary Amines to Aldehydes.

The direct oxidative cross-dehydrogenative coupling (CDC) of two C H bonds can be an efficient and relatively clean strategy in organic synthesis. Various sp C Hbonds, such as benzylic and allylic C H bonds, the a-C H bonds of amines and ethers, and the C H bonds of alkanes can be oxidized for direct reaction with carbon nucleophiles. Among these reactions, the oxidation of tertiary amines to generate iminium intermediates, as pioneered by Murahashi et al., Li et al. and others, has received considerable attention. Carbonyl compounds, such as 1,3-dicarbonyls, 10b,g] a,bunsaturated ketones, and simple ketones have been successfully coupled with tertiary amines by using metal catalysis, acid catalysis, metal/organic cooperative catalysis, or photoredox catalysis. In all of these reactions, the development of enantioselective catalysis remains a challenge. Very recently, Wang and co-workers used metals together with chiral bisoxazoline ligands to realize enantioselective reactions of activated carbonyl nucleophiles (such as 1,3dicarbonyls and acetyl phosphates) to oxidatively generate iminiums or their analogues. However, this approach with chiral ligands was found to be unsuccessful for reactions starting with simple ketone nucleophiles, as reported by Klussmann and co-workers as well as Xie and Huang. Approaches that use asymmetric enamine catalysis for the activation of carbonyl compounds have led to disappointing results (for example, less than 20% ee) as well . As part of a larger program for developing sustainable oxidation chemistry, we herein report an enantioselective oxidative coupling reaction of aldehydes and tertiary amines under cooperative amine and metal catalysis. The racemic version of this reaction was also realized by using metal catalysts alone (without amine catalysts), on account of its potential utility and the very different optimized conditions, relative to the enantioselective reactions. We examined metal-catalyzed oxidative coupling reactions between N-phenyltetrahydroisoquinoline (1a) and propionaldehyde (2a) in the presence of tBuOOH without an amine catalyst. An initial survey of solvents and catalysts indicated that DMF is a good solvent and CuBr2 is an effective metal catalyst (Table 1, entries 1–3, see also the Supporting Information). The amino aldehyde product 3a is unstable and, thus, was isolated as the corresponding amino alcohol product 4a in 72% yield after reduction with NaBH4 in situ, albeit with no diastereoselectivity (Table 1, entry 3). Under these conditions, various amines, such as N-aryl tetrahydroisoquinolines 1 and N,N-dialkyl anilines, and aldehydes 2 were used to obtain the corresponding racemic amino alcohols 4 in acceptable yields. Aldehydes with longer carbon chains required elevated reaction temperatures. N,Ndialkyl anilines gave the corresponding products in lower yields (Table S6 and Scheme S3 in the Supporting Information).

Enantioselective Oxidative Cross‐Dehydrogenative Coupling of Tertiary Amines to Aldehydes

The direct oxidative cross-dehydrogenative coupling (CDC) of two C H bonds can be an efficient and relatively clean strategy in organic synthesis. Various sp C Hbonds, such as benzylic and allylic C H bonds, the a-C H bonds of amines and ethers, and the C H bonds of alkanes can be oxidized for direct reaction with carbon nucleophiles. Among these reactions, the oxidation of tertiary amines to generate iminium intermediates, as pioneered by Murahashi et al., Li et al. and others, has received considerable attention. Carbonyl compounds, such as 1,3-dicarbonyls, 10b,g] a,bunsaturated ketones, and simple ketones have been successfully coupled with tertiary amines by using metal catalysis, acid catalysis, metal/organic cooperative catalysis, or photoredox catalysis. In all of these reactions, the development of enantioselective catalysis remains a challenge. Very recently, Wang and co-workers used metals together with chiral bisoxazoline ligands to realize enantioselective reactions of activated carbonyl nucleophiles (such as 1,3dicarbonyls and acetyl phosphates) to oxidatively generate iminiums or their analogues. However, this approach with chiral ligands was found to be unsuccessful for reactions starting with simple ketone nucleophiles, as reported by Klussmann and co-workers as well as Xie and Huang. Approaches that use asymmetric enamine catalysis for the activation of carbonyl compounds have led to disappointing results (for example, less than 20% ee) as well . As part of a larger program for developing sustainable oxidation chemistry, we herein report an enantioselective oxidative coupling reaction of aldehydes and tertiary amines under cooperative amine and metal catalysis. The racemic version of this reaction was also realized by using metal catalysts alone (without amine catalysts), on account of its potential utility and the very different optimized conditions, relative to the enantioselective reactions. We examined metal-catalyzed oxidative coupling reactions between N-phenyltetrahydroisoquinoline (1a) and propionaldehyde (2a) in the presence of tBuOOH without an amine catalyst. An initial survey of solvents and catalysts indicated that DMF is a good solvent and CuBr2 is an effective metal catalyst (Table 1, entries 1–3, see also the Supporting Information). The amino aldehyde product 3a is unstable and, thus, was isolated as the corresponding amino alcohol product 4a in 72% yield after reduction with NaBH4 in situ, albeit with no diastereoselectivity (Table 1, entry 3). Under these conditions, various amines, such as N-aryl tetrahydroisoquinolines 1 and N,N-dialkyl anilines, and aldehydes 2 were used to obtain the corresponding racemic amino alcohols 4 in acceptable yields. Aldehydes with longer carbon chains required elevated reaction temperatures. N,Ndialkyl anilines gave the corresponding products in lower yields (Table S6 and Scheme S3 in the Supporting Information).

ChemInform Abstract: Catalyst‐Controlled Wacker‐Type Oxidation of Homoallylic Alcohols in the Absence of Protecting Groups.

AbstractIn the presence of tBuOOH and the catalyst system, various homoallylic alcohols undergo selective oxidation to β‐hydroxyketones.

Complexes of a diacetylmonoxime Schiff base of S-methyldithiocarbazate (H2damsm) with Fe(III), Ru(III)/Ru(II), and V(IV); catalytic activity and X-ray crystal structure of [Fe(Hdamsm)2]NO3·H2O

The complexes [M(Hdamsm)2]X·H2O (M = Fe, X = NO3; M = Ru, X = Cl), [Ru(Hdamsm)(PPh3)2X′](X′ = Cl, Br), and [VO(Hdamsm)(acac)] (H2damsm = diacetylmonoxime Schiff base of S-methyldithiocarbazate, Hacac = acetylacetone) have been prepared and characterized by spectroscopic techniques. Their redox properties were investigated by cyclic voltammetry. The X-ray crystal structure of [Fe(Hdamsm)2]NO3.H2O has been determined and shows that the complex has a distorted octahedral geometry in which the Hdamsm behaves as a monoanionic NNS tridentate ligand coordinating via oxime nitrogen, hydrazinic imine nitrogen, and thiolate sulfur. The reactivity of these complexes toward oxidation of alcohols in the presence of t-BuOOH and H2O2 as co-oxidants is reported.

ChemInform Abstract: Catalytst‐Controlled Wacker‐Type Oxidation of Protected Allylic Amines.

AbstractAllylic amines are selectively oxidized to methyl ketones in the presence of tBuOOH and the [2‐(oxazolin‐2‐yl)quinoline]palladium catalyst.

Microwave-enhanced radical reactions at ambient temperature : Part 3: Highly selective radical synthesis of 3-cyclohexyl-1-phenyl-1-butanone in a microwave double cylindrical cooled reactor

The microwave-enhanced synthesis of 3-cyclohexyl-1-phenyl-1-butanone (CPB) from crotonophenone and iodocyclohexane in the presence of t-BuOOH and triethylborane was examined at ambient temperature and under reflux conditions in bulk solution using no less than four different synthetic protocols. Chemical yields of CPB (93 and 95%, respectively) obtained after 60 and 120 min under microwave dielectric heating coupled to a cooling system (MW/Cool protocol) for a reaction temperature of 20–24 °C exceeded the yields from the reaction occurring at room temperature (24 °C; no microwaves; 40% and 72%) for the same reaction times and temperature. The competitive radical reaction to produce CPB and a small amount of by-products generated from the thermally-induced synthesis by the non-selective radical reaction was restricted solely to the process occurring at ambient temperature (RT protocol), under microwave dielectric heating to reflux (MW protocol) and heating with an oil-bath also to reflux (Oil-bath protocol). By contrast, no by-products were generated or detected for the reaction taking place by the MW/Cool method. Comparison of product yields under conditions of identical temperature conditions must involve some specific microwave effect in the synthesis of the title compound.