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One-Pot Biocatalytic In Vivo Methylation-Hydroamination of Bioderived Lignin Monomers to Generate a Key Precursor to L-DOPA
Electron-rich phenolic substrates can be derived from the depolymerisation of lignin feedstocks. Direct biotransformations of the hydroxycinnamic acid monomers obtained can be exploited to produce high-value chemicals, such as α-amino acids, however the reaction is often hampered by the chemical autooxidation in alkaline or harsh reaction media. Regioselective O-methyltransferases (OMTs) are ubiquitous enzymes in natural secondary metabolic pathways utilising an expensive co-substrate S-adenosyl-l-methionine (SAM) as the methylating reagent altering the physicochemical properties of the hydroxycinnamic acids. In this study, we engineered an OMT to accept a variety of electron-rich phenolic substrates, modified a commercial E. coli strain BL21 (DE3) to regenerate SAM in vivo, and combined it with an engineered ammonia lyase to partake in a one-pot, two whole cell enzyme cascade to produce the l-DOPA precursor l-veratrylglycine from lignin-derived ferulic acid.
Birmingham, William R.,Galman, James L.,Parmeggiani, Fabio,Seibt, Lisa,Turner, Nicholas J.
(2022/01/13)

Preparation method of 3-hydroxy-4-methoxyphenylpropylaldehyde
The invention provides a preparation method of 3-hydroxy-4-methoxyphenylpropylaldehyde. The preparation method comprises the following steps: 1, ring opening: subjecting sassafras oil, methanol and an alkaline reagent to a reaction to obtain a phenol potassium salt solution; 2, etherification: subjecting the phenol potassium salt solution to reacting with an excessive methylation reagent to obtain mixed ether; 3, hydrolysis: subjecting the mixed ether to reacting with alcohol, water and a catalyst to obtain a hydrolyzed oil phase; 4, esterification: subjecting the hydrolyzed oil phase to reacting with acetic anhydride to obtain an acetyl intermediate product; 5, ozonization and reduction: subjecting the acetyl product to reacting with ozone, and adding a pyrosulfite solution for reduction to obtain a reduced oil phase; 6, alcoholysis: performing alcoholysis on the oil phase obtained in the step 5 to obtain a crude isovanillin product; 7, condensation; and 8, hydrogenation. The preparation method solves the problems that isovanillin is few in source and high in price, and production of a 3-hydroxy-4-methoxyphenylpropyl aldehyde intermediate is limited in the prior art, and has the advantages of being high in yield and low in cost.
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Paragraph 0048-0054; 0058-0065; 0068-0075; 0078-0085

(2021/11/10)

Method for synthesizing isovanillin
The invention provides a method for synthesizing isovanillin, and belongs to the technical field of chemical engineering. The method for synthesizing isovanillin comprises the steps of (1) conducting a methylation reaction, specifically, adding ethyl vanillin, dimethyl sulfoxide, Pd (OAc) 2 and a sodium hydroxide solution into a reaction kettle, carrying out oxygen replacement, controlling the oxygen pressure at 0.2 MPa, reacting at the temperature of 100 DEG C for 6 hours, ending the reaction, and filtering and separating the reaction liquid to obtain an oil-phase intermediate; (2) conducting a hydrolysis reaction, specifically, adding the oil-phase intermediate, a SO4/ZrOTiO2 catalyst and water into the reaction kettle, reacting at the temperature of 65 DEG C, and ending the reaction; carrying out suction filtration on the reaction liquid, dissolving a filter cake with 2000g of ethanol, carrying out heat preservation stirring at the temperature of 60 DEG C for 2-6 hours, and carrying out suction filtration; cooling the filtrate to 0 DEG C, preserving heat and stirring for 2-6 hours, and performing suction filtration to obtain a wet product; and drying the obtained solid in vacuum until the weight is constant to obtain the isovanillin.
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Paragraph 0019; 0031-0039; 0041-0051

(2021/07/31)

Thiols Act as Methyl Traps in the Biocatalytic Demethylation of Guaiacol Derivatives
Demethylating methyl phenyl ethers is challenging, especially when the products are catechol derivatives prone to follow-up reactions. For biocatalytic demethylation, monooxygenases have previously been described requiring molecular oxygen which may cause oxidative side reactions. Here we show that such compounds can be demethylated anaerobically by using cobalamin-dependent methyltransferases exploiting thiols like ethyl 3-mercaptopropionate as a methyl trap. Using just two equivalents of this reagent, a broad spectrum of substituted guaiacol derivatives were demethylated, with conversions mostly above 90 %. This strategy was used to prepare the highly valuable antioxidant hydroxytyrosol on a one-gram scale in 97 % isolated yield.
Grimm, Christopher,Kroutil, Wolfgang,Pompei, Simona,Schiller, Christine,Schober, Lukas
supporting information
p. 16906 - 16910
(2021/07/02)

Regioselectivity of Cobalamin-Dependent Methyltransferase Can Be Tuned by Reaction Conditions and Substrate
Regioselective reactions represent a significant challenge for organic chemistry. Here the regioselective methylation of a single hydroxy group of 4-substituted catechols was investigated employing the cobalamin-dependent methyltransferase from Desulfitobacterium hafniense. Catechols substituted in position four were methylated either in meta- or para-position to the substituent depending whether the substituent was polar or apolar. While the biocatalytic cobalamin dependent methylation was meta-selective with 4-substituted catechols bearing hydrophilic groups, it was para-selective for hydrophobic substituents. Furthermore, the presence of water miscible co-solvents had a clear improving influence, whereby THF turned out to enable the formation of a single regioisomer in selected cases. Finally, it was found that also the pH led to an enhancement of regioselectivity for the cases investigated.
Pompei, Simona,Grimm, Christopher,Farnberger, Judith E.,Schober, Lukas,Kroutil, Wolfgang
p. 5977 - 5983
(2020/10/06)

Engineering Orthogonal Methyltransferases to Create Alternative Bioalkylation Pathways
S-adenosyl-l-methionine (SAM)-dependent methyltransferases (MTs) catalyse the methylation of a vast array of small metabolites and biomacromolecules. Recently, rare carboxymethylation pathways have been discovered, including carboxymethyltransferase enzymes that utilise a carboxy-SAM (cxSAM) cofactor generated from SAM by a cxSAM synthase (CmoA). We show how MT enzymes can utilise cxSAM to catalyse carboxymethylation of tetrahydroisoquinoline (THIQ) and catechol substrates. Site-directed mutagenesis was used to create orthogonal MTs possessing improved catalytic activity and selectivity for cxSAM, with subsequent coupling to CmoA resulting in more efficient and selective carboxymethylation. An enzymatic approach was also developed to generate a previously undescribed co-factor, carboxy-S-adenosyl-l-ethionine (cxSAE), thereby enabling the stereoselective transfer of a chiral 1-carboxyethyl group to the substrate.
Bennett, Matthew R.,Cronin, Victoria A.,Herbert, Abigail J.,Micklefield, Jason,Shepherd, Sarah A.,Sung, Rehana
supporting information
p. 14950 - 14956
(2020/07/04)

Oxygen-Free Regioselective Biocatalytic Demethylation of Methyl-phenyl Ethers via Methyltransfer Employing Veratrol- O-demethylase
The cleavage of aryl methyl ethers is a common reaction in chemistry requiring rather harsh conditions; consequently, it is prone to undesired reactions and lacks regioselectivity. Nevertheless, O-demethylation of aryl methyl ethers is a tool to valorize natural and pharmaceutical compounds by deprotecting reactive hydroxyl moieties. Various oxidative enzymes are known to catalyze this reaction at the expense of molecular oxygen, which may lead in the case of phenols/catechols to undesired side reactions (e.g., oxidation, polymerization). Here an oxygen-independent demethylation via methyl transfer is presented employing a cobalamin-dependent veratrol-O-demethylase (vdmB). The biocatalytic demethylation transforms a variety of aryl methyl ethers with two functional methoxy moieties either in 1,2-position or in 1,3-position. Biocatalytic reactions enabled, for instance, the regioselective monodemethylation of substituted 3,4-dimethoxy phenol as well as the monodemethylation of 1,3,5-trimethoxybenzene. The methyltransferase vdmB was also successfully applied for the regioselective demethylation of natural compounds such as papaverine and rac-yatein. The approach presented here represents an alternative to chemical and enzymatic demethylation concepts and allows performing regioselective demethylation in the absence of oxygen under mild conditions, representing a valuable extension of the synthetic repertoire to modify pharmaceuticals and diversify natural products.
Grimm, Christopher,Lazzarotto, Mattia,Pompei, Simona,Schichler, Johanna,Richter, Nina,Farnberger, Judith E.,Fuchs, Michael,Kroutil, Wolfgang
p. 10375 - 10380
(2020/10/02)

Specific Residues Expand the Substrate Scope and Enhance the Regioselectivity of a Plant O-Methyltransferase
An isoeugenol 4-O-methyltransferase (IeOMT), isolated from the plant Clarkia breweri, can be engineered to a caffeic acid 3-O-methyltransferase (CaOMT) by replacing three consecutive residues. Here we further investigated functions of these residues by constructing the triple mutant T133M/A134N/T135Q as well as single mutants of each residue. Phenolics with different chain lengths and different functional groups were investigated. The variant T133M improves the enzymatic activities against all tested substrates by providing beneficial interactions to residues which directly interact with the substrate. Mutant A134N significantly enhanced the regioselectivity. It is meta-selective or even specific against most of the tested substrates but para-specific towards 3,4-dihydroxybenzoic acid. The triple mutant T133M/A134N/T135Q benefits from these two mutations, which not only expand the substrate scope but also enhance the regioselectivity of IeOMT. On the basis of our work, regiospecific methylated phenolics can be produced in high purity by different IeOMT variants.
Tang, Qingyun,Bornscheuer, Uwe T.,Pavlidis, Ioannis V.
p. 3227 - 3233
(2019/07/04)

Benzylideneacetone Derivatives Inhibit Osteoclastogenesis and Activate Osteoblastogenesis Independently Based on Specific Structure-Activity Relationship
(E)-3,4-Dihydroxybenzylideneacetone (compound 1) inhibited receptor activator of NF-κB ligand-induced osteoclastogenesis of C57BL/6 bone marrow monocyte/macrophages with IC50 of 7.8 μM (IC50 of alendronate, 3.7 μM) while stimulating the differentiation of MC3T3-E1 osteoblastic cells, accompanied by the induction of Runt-related transcription factor 2, alkaline phosphatase, and osteocalcin. (E)-4-(3-Hydroxy-4-methoxyphenyl)-3-buten-2-one (compound 2c) showed a dramatically increased osteoclast-inhibitory potency with IC50 of 0.11 μM while sustaining osteoblast-stimulatory activity. (E)-4-(4-Hydroxy-3-methoxyphenyl)-3-buten-2-one (compound 2g) stimulated alkaline phosphatase production 2-fold at 50 μM without changing osteoclast-inhibitory activity, compared with compound 1. Oral administration of compounds 1, 2c, and 2g prevented ovariectomy-induced osteoporosis in ddY mice to a degree proportional to their osteoclastogenesis-inhibitory potencies. The administration of 1 (mg/kg)/d compound 2c ameliorated histomorphometry of osteoporotic bone to a degree comparable with 10 (mg/kg)/d alendronate. Conclusively, the in vitro capacity of a few benzylideneacetone derivatives to inhibit osteoclastogenesis supported by independent osteoblastogenesis activation was convincingly reflected in in vivo management of osteoporosis, suggesting a potential novel therapeutics for osteopenic diseases.
Pativada, Triveni,Kim, Myung Hwan,Lee, Jung-Hun,Hong, Seong Su,Choi, Chun Whan,Choi, Yun-Hyeok,Kim, Woo Jung,Song, Da-Woon,Park, Serk In,Lee, Eun Jung,Seo, Bo-Yeon,Kim, Hankyeom,Kim, Hong Kyu,Lee, Kee Ho,Ahn, Sung K.,Ku, Jin-Mo,Park, Gil Hong
p. 6063 - 6082
(2019/08/02)

Degradation of lignin with aqueous ammonium-based ionic liquid solutions under milder conditions
This study investigates the performance of two aqueous ionic liquids (ILs), dimethylbutylammonium acetate ([DMBA][Ac]) and dimethylbutylammonium butanoate ([DMBA][B]), solutions for depolymerizing alkali lignin into valuable phenolic compounds. The favorable operation conditions, including reaction temperature and reaction time, are explored. The extent of depolymerization of the lignin is evaluated by analysis with gel permeation chromatography (GPC). The results show that the average molecular weights of the depolymerized lignin samples can be reduced by as high as 93.8% and 86.8% after treating with the aqueous [DMBA][Ac] and [DMBA][B], respectively. Moreover, the aromatic chemical species in the depolymerized solutions are identified by using gas chromatography?mass spectrophotometry (GC-MS). The confirmation of the chemical species is further made by using a series of spectroscopic techniques, such as FT-IR, and 1H NMR and 13C NMR spectroscopy. Promising results have been achieved for the depolymerization of the lignin into valuable chemicals by using the proposed green media, aqueous solutions of ionic liquids [DMBA][Ac] and [DMBA][B], under milder conditions.
Gupta, Bhupender S.,Lee, Ming-Jer,Tolesa, Leta Deressa
p. 3357 - 3365
(2019/02/25)

Coenzyme A-Conjugated Cinnamic Acids – Enzymatic Synthesis of a CoA-Ester Library and Application in Biocatalytic Cascades to Vanillin Derivatives
We present a bioorthogonal method for the ligation of coenzyme A (CoA) with cinnamic acids. The reaction, which is the initial step in the biosynthesis of a multitude of bioactive secondary metabolites, is catalyzed by a promiscuous plant ligase and yields CoA conjugates with different functionalization in high purity and without formation of by-products. Its applicability in biosynthetic cascades is shown for the direct transformation of cinnamic acids into natural benzaldehydes (like vanillin) or artificial derivatives (e. g. ethylvanillin). (Figure presented.).
Dippe, Martin,Bauer, Anne-Katrin,Porzel, Andrea,Funke, Evelyn,Müller, Anna O.,Schmidt, Jürgen,Beier, Maria,Wessjohann, Ludger A.
supporting information
p. 5346 - 5350
(2019/11/29)

Aerobic alcohol oxidation catalyzed by CuO-rectorite/TEMPO in water
An environmentally benign CuO-rectorite was prepared by calcining the co-precipitation product of Cu2+ with an acid-activated rectorite at pH 6. It could be well dispersed in water and used as a co-catalyst with TEMPO to selectively aerobically oxidize alcohols to aldehydes. The conversion of most primary benzylic alcohols was very high under optimized conditions. Interestingly, the oxidation protocol also allowed highly selective transformation of benzylic alcohols containing a phenolic hydroxyl group into the corresponding aldehydes. Additionally, very little copper was leached from the catalyst during the catalytic reaction. CuO-rectorite could be reused by centrifugation and washed with acetonitrile and water. At the same time, its catalytic activity remained high.
Liu, Wanghui,Yang, Jianhong,Cai, Jun
p. 549 - 561
(2018/10/15)

Synthesis of a Photo-Caged DOPA Derivative by Selective Alkylation of 3,4-Dihydroxybenzaldehyde
Natural and synthetic polymers containing the catechol moiety of noncoded amino acid 3,4-dihydroxyphenylalanine (DOPA) are capable of metal-coordination and adhesion under wet conditions. Masking the catechol subunit with a photo-cleavable group would provide an opportunity to design tunable adhesion properties that are especially important for biomaterial and biomedicine applications. Herein, we report the regioselective synthesis of a photo-caged DOPA bearing an ortho-nitrobenzyl (oNB) group that is capable of undergoing cleavage upon irradiation with UV light. We developed a selective synthetic route towards a 3-O-oNB alkylated DOPA regioisomer that can be readily incorporated into proteins by using a previously developed bio-expression platform. The synthesis is based on a regioselectivity switch in 3,4-dihydrozybenzaldehyde alkylation upon application of different equivalents of deprotonating base. The enantiomerically pure 3-O-oNB-DOPA was prepared on a gram scale and proved to be generally compatible with the solid-phase peptide synthesis conditions. We also demonstrate the general applicability of the developed synthetic strategy by providing the synthesis of 3-O-methyl-DOPA.
Schneider, Tobias,Kubyshkin, Vladimir,Budisa, Nediljko
p. 2053 - 2063
(2018/05/31)

Phosphinous Acid Platinum Complex as Robust Catalyst for Oxidation: Comparison with Palladium and Mechanistic Investigations
Secondary phosphine oxides proved to be effective preligands to stabilise a hydroxy-platinum based catalyst that allows the aerobic/anaerobic oxidation of challenging substrates. Kinetic comparisons showed that this system is more efficient and stable than previously reported similar palladium-based catalysts. A neutral platinum dimer bearing bridging hydroxy ligands has been isolated and fully characterised by X-ray diffraction and its involvement in the mechanism has been evidenced by mechanistic studies.
Membrat, Romain,Vasseur, Alexandre,Martinez, Alexandre,Giordano, Laurent,Nuel, Didier
supporting information
p. 5427 - 5434
(2018/10/20)

Novel synthetic process of isovanillin
The invention discloses a novel synthetic process of isovanillin, and relates to the field of organic synthesis technology. The method comprises: reacting 4-hydroxybenzaldehyde as a raw material with bromine to obtain 3-bromo 4-hydroxybenzaldehyde, reacting with methyl iodide to obtain 3-bromo-4-methoxy benzaldehyde, and then performing hydrolysis to obtain the isovanillin under the action of sodium hydroxide and cuprous chloride. The method adopts cheap and easily obtained 4-hydroxybenzaldehyde as the starting material, the isovanillin is obtained under mild reaction conditions, and the economic efficiency of a process is improved while the cost is reduced. The total yield of the product, isovanillin, obtained by using the optimum process is up to 64.1%, the conversion rates of the raw materials in each step are significantly increased, and the method is suitable for industrial production.
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Paragraph 0015; 0032; 0036; 0040; 0044; 0048

(2017/09/18)

A (3 - alkoxy - 4 - hydroxy) - cyclohexyl acetal glycol and its isomers of use
The present invention discloses a (3-alkoxy-4-hydroxy)-cyclohexyl methylal diol, an (3-hydroxy-4-alkoxy)-cyclohexyl methylal diol and synthesis methods and use therefor. The (3-alkoxy-4-hydroxy)-cyclohexyl methylal diol and (3-hydroxy-4-alkoxy)-cyclohexyl methylal diol can be used for synthesis of a variety of vanillin and iso-vanillin. Compared to the existing synthetic method, the synthesis method has simple steps, and less discharge of "three wastes".
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(2017/08/26)

A 3, 4 - epoxy-cyclohexane METHYLAL glycol and its synthesis and use
The invention discloses a 3,4-epoxy cyclohexyl methylal diol and a synthesis method thereof. The 3,4-epoxy cyclohexyl methylal diol can be used for synthesizing multiple vanillins and isovanillins. Compared with the existing synthesis process, the synthesis method disclosed by the invention has the advantages of simple steps and low discharge amount of three wastes.
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(2017/11/16)

Catalytic Alkylation Using a Cyclic S-Adenosylmethionine Regeneration System
S-Adenosylmethionine-dependent methyltransferases are versatile tools for the specific alkylation of many compounds, such as pharmaceuticals, but their biocatalytic application is severely limited owing to the lack of a cofactor regeneration system. We report a biomimetic, polyphosphate-based, cyclic cascade for methyltransferases. In addition to the substrate to be methylated, only methionine and polyphosphate have to be added in stoichiometric amounts. The system acts catalytically with respect to the cofactor precursor adenosine in methylation and ethylation reactions of selected substrates, as shown by HPLC analysis. Furthermore, 1H and 13C NMR measurements were performed to unequivocally identify methionine as the methyl donor and to gain insight into the selectivity of the reactions. This system constitutes a vital stage in the development of economical and environmentally friendly applications of methyltransferases.
Mordhorst, Silja,Siegrist, Jutta,Müller, Michael,Richter, Michael,Andexer, Jennifer N.
supporting information
p. 4037 - 4041
(2017/03/27)

A Green, Solvent-Free, Microwave-Assisted, High-Yielding YbCl3Catalyzed Deprotection of THP/MOM/Ac/Ts Ethers of Chalcone Epoxide and 2′-Aminochalcone and Their Sequel Cyclization
Under microwave and solvent-free conditions, YbCl3efficiently catalyzed the deprotection of tetrahydropyran-2-yl, methoxymethyl (MOM), acetyl, and tosyl groups and sequel cyclization of chalcone epoxide to 2-hydroxyindanone and 2′-aminochalcone to aza-flavanone. The reaction afforded the products in excellent yield (78–99%) at 850 W microwave heating within 1–5 min under eco-friendly conditions. The merits of the presented protocol include high yield, use of microwave irradiation, solvent-free condition, catalyst reusability, and no need for purification with column chromatography. The present method is very much milder but more advanced than those reported earlier.
Kumar, Sumit,Verma, Nishant,Parveen, Iram,Ahmed, Naseem
supporting information
p. 2111 - 2122
(2016/11/23)

β-Cyclodextrin in water: Highly facile biomimetic one pot deprotection of phenolic THP/MOM/Ac/Ts ethers and concomitant regioselective cyclization of chalcone epoxides and 2′-aminochalcones
A mild and efficient one-pot deprotection of THP/MOM/Ac/Ts ethers and the concomitant cyclization of chalcone epoxides to 2-hydroxyindanones or 2′-aminochalcones to aza-flavanones using β-cyclodextrin in water has been developed. β-CD was found to be highly effective at carrying out the deprotection and sequential transformations in an eco-friendly environment affording moderate to excellent yields (59-99%) at 60 °C in 8-22 min. Water, an eco-friendly reaction medium, has been utilized for the first time in this reaction. The merits of the presented protocol include the high yields and catalyst reusability and the protocol precludes the use of metals and organic solvents. The present method is much milder but more advanced than those reported earlier.
Kumar, Sumit,Verma, Nishant,Ahmed, Naseem
p. 85128 - 85138
(2015/10/28)

Improved selectivity of the production of vanilloids in a recombinant unicellular host
The present invention relates to methods for producing vanilloid compounds in a recombinant host, and in particular for converting a protocatechuic aldehyde into a substantially pure vanilloid. It further relates to novel yeast strains that are suitable for producing such vanilloid compounds.
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Paragraph 0206-0209; 0216

(2016/01/11)

Practical Ligand-Free Copper-Catalysed Short-Chain Alkoxylation of Unactivated Aryl Bromides
An efficient and practical short-chain alkoxylation of unactivated aryl bromides has been developed with special attention focussed on the applicability of the reaction. Sodium alkoxide is used as the nucleophile, and the corresponding alcohol as the solvent. The reaction requires neither precious metals nor organic ligands. It uses a catalytic system consisting of copper(I) bromide as a catalyst, the corresponding alkyl formate as a noncontaminating cocatalyst, and lithium chloride as an additive. A wide range of substrates and test cases highlight the synthetic utility of the approach. Considering the commercial accessibility and affordability of the feedstocks, this protocol shows promise as a new alternative for the sustainable preparation of aryl alkyl ethers.
Guo, Ying,Fan, Xue-Min,Nie, Min,Liu, Hong-Wei,Liao, Dao-Hua,Pan, Xian-Dao,Ji, Ya-Fei
p. 4744 - 4755
(2015/08/03)

Enzymatic allylation of catechols
Enzymatic allylation of catechols was realized via catechol O-methyltransferase (COMT) using an allylated S-adenosyl- L-methionine (allyl-SAM) analog, with relatively good chemoand regioselectivities. This new reaction offered an alternative procedure for allylation of catechols, which can be expanded as a biocatalytic allylation method in organic synthesis.
Zhang, Yixin,Liu, Wujun,Sohail, Muhammad,Wang, Xueying,Liu, Yuxue,Zhao, Zongbao K.
supporting information
p. 949 - 951
(2015/08/24)

Computational and Experimental Studies of Phthaloyl Peroxide-Mediated Hydroxylation of Arenes Yield a More Reactive Derivative, 4,5-Dichlorophthaloyl Peroxide
The oxidation of arenes by the reagent phthaloyl peroxide provides a new method for the synthesis of phenols. A new, more reactive arene oxidizing reagent, 4,5-dichlorophthaloyl peroxide, computationally predicted and experimentally determined to possess enhanced reactivity, has expanded the scope of the reaction while maintaining a high level of tolerance for diverse functional groups. The reaction proceeds through a novel "reverse-rebound" mechanism with diradical intermediates. Mechanistic insight was achieved through isolation and characterization of minor byproducts, determination of linear free energy correlations, and computational analysis of substituent effects of arenes, each of which provided additional support for the reaction proceeding through the diradical pathway.
Camelio, Andrew M.,Liang, Yong,Eliasen, Anders M.,Johnson, Trevor C.,Yuan, Changxia,Schuppe, Alex W.,Houk,Siegel, Dionicio
p. 8084 - 8095
(2015/09/01)

In situ one-step synthesis of metal-organic framework encapsulated naked Pt nanoparticles without additional reductants
The encapsulation of metal nanoparticles (MNPs) into metal-organic frameworks has generated recent research because of the promising novel physical and chemical properties originating from synergetic interactions between MNPs and MOFs. However, the development of a facile one-step approach for the incorporation of tiny MNPs within MOFs without additional stabilizing agents and reductants remains a great challenge. Herein, we report a new and general synthesis strategy for MNPs@MOFs that allows preferential self-assembly of MOFs around the in situ formed MNP surface by directly mixing both the reactive metal (e.g., H2PtCl6) and MOF precursors in DMF. This in situ one-step assembly approach is applicable to various MOFs, affording well-defined Pt@MOF composites with highly dispersed naked Pt NPs in narrow diameter distribution. The resulting Pt@MOF nanocomposites exhibit excellent stability, significantly enhanced catalytic activity and selectivity as compared to the commercial Pt/C in liquid-phase aerobic oxidation of alcohols.
Liu, Hongli,Chang, Lina,Chen, Liyu,Li, Yingwei
p. 8028 - 8033
(2015/04/14)

Debenzylation of vanillic acid over sulfosuccinic acid functionalized mesoporous silica nanocomposites
Sulfosuccinic acid functionalized mesoporous silica (SBA/SSA) was synthesized and characterized for debenzylation of vanillic acid in liquid phase for the first time. The catalytic activity studies showed high activity (82%) and selectivity (96%) for the desired product vanillic acid over SBA/SSA compared to 74% selectivity over silica/SSA. Synergistic effects of acidic/basic groups responsible for higher activity and selectivity were explained with plausible mechanism.
Sachdev, Divya,Wilson, G. Robin,Srivastava, Neel Mani,Dubey, Amit
p. 90 - 94
(2014/05/06)

CYCLIC PEROXIDE OXIDATION OF AROMATIC COMPOUND PRODUCTION AND USE THEREOF
The present invention provides a method for converting an aromatic hydrocarbon to a phenol by providing an aromatic hydrocarbon comprising one or more aromatic C-H bonds and one or more activated C-H bonds in a solvent; adding a phthaloyl peroxide to the solvent; converting the phthaloyl peroxide to a di-radical; contacting the di-radical with the one or more aromatic C-H bonds; oxidizing selectively one of the one or more aromatic C-H bonds in preference to the one or more activated C-H bonds; adding a hydroxyl group to the one of the one or more aromatic C-H bonds to form one or more phenols; and purifying the one or more phenols.
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Page/Page column 10

(2014/10/15)

A new method for the facile synthesis of hydroxylated flavones by using allyl protection
The iodine-induced oxidative cyclization of 2′-hydroxychalcones provides a simple, highly efficient approach to various hydroxy flavones and analogues. This process is run under mild conditions, tolerates various functional groups, and provides hydroxy flavones in good to excellent yield. The allyl-protected acetophenones and benzaldehydes were smoothly deallylated under similar conditions.
Nawghare,Sakate,Lokhande
p. 291 - 302
(2014/04/17)

Practical Cu(OAc)2/TEMPO-catalyzed selective aerobic alcohol oxidation under ambient conditions in aqueous acetonitrile
We reported a ligand-and additive-free Cu(OAc)2/TEMPO catalyst system that enables efficient and selective aerobic oxidation of a broad range of primary and secondary benzylic alcohols, primary and secondary 1-heteroaryl alcohols, cinnamyl alcohols, and aliphatic alcohols to the corresponding aldehydes and ketones. This ambient temperature oxidation protocol is of practical features like aqueous acetonitrile as solvent, ambient air as the terminal oxidant, and low catalyst loading, presenting a potential value in terms of both economical and environmental considerations. Based on the experimental observations, a plausible reaction mechanism was proposed.
Jiang, Jian-An,Du, Jia-Lei,Wang, Zhan-Guo,Zhang, Zhong-Nan,Xu, Xi,Zheng, Gan-Lin,Ji, Ya-Fei
supporting information
p. 1677 - 1681
(2014/03/21)

Aerobic oxidation of alcohols by using a completely metal-free catalytic system
A metal-free reaction system of air, NH4NO3(cat), 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)(cat), and H +(cat) is introduced as a simple, safe, inexpensive, efficient and chemoselective mediator for aerobic oxidation of various primary and secondary benzyl and alkyl alcohols, including those bearing oxidizable heteroatoms (N, S, O) to the corresponding aldehydes or ketones. Air oxygen under slight overpressure plays the role of the terminal oxidant, which is catalytically activated by redox cycles of nitrogen oxides released from a catalytic amount of NH4NO3 and cocatalyzed by TEMPO (nitroxyl radical compound), under acidic conditions, which are essential for an overall activation of the reaction system. The synthetic value of this reaction system and its green chemical profile was illustrated by a 10 g scale-up experiment, performed in an open-air system by using a renewable and reusable polymer-supported form of TEMPO (OXYNITROXS100). The reaction solvent was recovered by distillation under atmospheric pressure, and the pure final product was isolated under reduced pressure; the acid activators (HCl or H 2SO4) were recovered as ammonium salts. A metal-free reaction system of air/NH4NO3(cat)/TEMPO (cat)/H+(cat) is introduced as a simple, safe, inexpensive, efficient and chemoselective mediator for aerobic oxidation of various primary and secondary benzyl, alkyl and allyl alcohols, including those bearing oxidizable heteroatoms (N, S, O) to the corresponding aldehydes or ketones. Copyright
Prebil, Rok,Stavber, Gaj,Stavber, Stojan
supporting information
p. 395 - 402
(2014/01/23)

Aerobic Oxidation of Alcohols by Using a Completely Metal-Free Catalytic System
A metal-free reaction system of air, NH4NO3(cat), 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)(cat), and H+(cat) is introduced as a simple, safe, inexpensive, efficient and chemoselective mediator for aerobic oxidation of various primary and secondary benzyl and alkyl alcohols, including those bearing oxidizable heteroatoms (N, S, O) to the corresponding aldehydes or ketones. Air oxygen under slight overpressure plays the role of the terminal oxidant, which is catalytically activated by redox cycles of nitrogen oxides released from a catalytic amount of NH4NO3 and cocatalyzed by TEMPO (nitroxyl radical compound), under acidic conditions, which are essential for an overall activation of the reaction system. The synthetic value of this reaction system and its green chemical profile was illustrated by a 10 g scale-up experiment, performed in an open-air system by using a renewable and reusable polymer-supported form of TEMPO (OXYNITROXS100). The reaction solvent was recovered by distillation under atmospheric pressure, and the pure final product was isolated under reduced pressure; the acid activators (HCl or H2SO4) were recovered as ammonium salts.
Prebil, Rok,Stavber, Gaj,Stavber, Stojan
supporting information
p. 395 - 402
(2015/10/05)

Concurrent synthesis of vanillin and isovanillin
A method for concurrent synthesis of vanillin and isovanillin has been developed by a nonregioselective Vilsmeier-Haack reaction of O-alkyl guaiacols. O-Alkylation of guaiacol provided the corresponding O-alkyl guaiacol (1), which was then formylated with N-methylformanilide/phosphorus oxychloride to give a mixture of 4-alkoxy-3-methoxy-benzaldehyde (2) and 3-alkoxy-4- methoxybenzaldehyde (3). Finally, the obtained mixture underwent a selective dealkylation by anhydrous aluminium trichloride, while leaving methyl groups intact to simultaneously achieve the significant fine chemicals vanillin and isovanillin.
Huang, Wei-Bin,Du, Cai-Yan,Jiang, Jian-An,Ji, Ya-Fei
p. 2849 - 2856
(2013/07/26)

Copper catalyzed selective oxidation of benzyl alcohol to benzaldehyde
Selective oxidation of benzyl alcohols was observed in presence of allyl,-CH3 and phenolic-OH group. The reaction of primary benzylic alcohols was very clean using 2 moles of copper chloride in THF for 2 hrs at 80°C . The only product identified was benzaldehydes. It was observed that the reaction times for electron releasing arenes were significantly shorter. The reaction time for o-hydroxybenzaldehydes required longer reaction time which might be attributed to co-ordination of the phenolic OH group with copper chlorides. Secondary benzylic alcohols gave very clean and high yield of ketones for example the oxidation benzoin required only half an hour to reach completion with 100% yield. Similarly 2'-allyloxybenzyl alcohols undergo oxidation reaction to gave high yields of 2'-allyloxybenzaldehyde without any change in allyl group like deallylation, isomerization and addition to alkene bond.
Lokhande, Pradeep D.,Waghmare, Smita R.,Gaikwad, Harsh,Hankare
p. 539 - 541
(2013/01/15)

Hypervalent iodine-mediated oxygenative phenol dearomatization reactions
Both λ3- and λ5-iodanes have proven to be useful reagents in the oxygenative dearomatization of phenols, and exploitations of their chemistry in the conception of both substrate- and reagent-controlled asymmetric variants of such a transformation of great value for natural product synthesis have shown evident signs of success. Moreover, the use of stabilized IBX (i.e., SIBX) in our methodology for O-demethylation of 2-methoxyphenols, which relies on the same key oxygenating dearomatization event, is reported here to be much more efficacious than that of IBX itself in the chemoselective one-step conversion of homovanillyl alcohol into hydroxytyrosol, and bergenin into norbergenin.
Pouységu, Laurent,Sylla, Tahiri,Garnier, Tony,Rojas, Luis B.,Charris, Jaime,Deffieux, Denis,Quideau, Stéphane
experimental part
p. 5908 - 5917
(2010/09/09)

H2O2/phosphonium ionic liquid: An efficient and simple approach for benzyl halides oxidation
An efficient oxidation of benzyl halide has been done using aqueous hydrogen peroxide (30%) in trihexyl(tetradecyl)phosphonium-tetrafluroborate ionic liquid the protocol is simple mild offering excellent yield of product.
Dake, Satish A.,Kulkarni, Ravibhushan S.,Rode, Ambadas B.,Shinde, Pravin S.,Ghumbre, Sushil K.,Magar, Rupali L.,Pawar, Rajendra P.
experimental part
p. 491 - 494
(2011/09/14)

Regioselective alkylation of catechols via Mitsunobu reactions
A mild and efficient Mitsunobu protocol for the regioselective alkylation of catechols such as 3,4-dihydroxybenzaldehyde and methyl 3,4-dihydroxybenzoate is described. The para-alkylation products could be easily prepared via the Mitsunobu reaction with high selectivity in moderate to good yields. Georg Thieme Verlag Stuttgart - New York.
Wang, Xiaolong,Ju, Tingting,Li, Xiaodong,Cao, Xiaoping
experimental part
p. 2947 - 2949
(2011/02/22)

Selective demethylation and debenzylation of aryl ethers by magnesium iodide under solvent-free conditions and its application to the total synthesis of natural products
An efficient selective demethylation and debenzylation method for aryl methyl/benzyl ethers using magnesium iodide under solvent-free conditions has been developed and applied to the synthesis of natural flavone and biphenyl glycosides. A variety of functional groups including glycoside were tolerated under the reaction conditions. Experimental results indicated that the removal of an O-benzyl group was easier than that of an O-methyl group, regardless of wherever they were meta or para to the carbonyl. Thus selective debenzylation can be achieved for substrates bearing both benzyloxy and methoxy groups.
Bao, Kai,Fan, Aixue,Dai, Yi,Zhang, Liang,Zhang, Weige,Cheng, Maosheng,Yao, Xinsheng
scheme or table
p. 5084 - 5090
(2010/04/03)

Phosphonium ionic liquid: A novel catalyst for benzyl halide oxidation
An environmentally friendly ionic liquid is used for the first time in mild and selective oxidation of aryl halides to corresponding aldehydes using iodoxybenzoic acid as oxidizing agent. Copyright Taylor & Francis Group, LLC.
Dake, Satish A.,Kulkarni, Ravibhushan S.,Kadam, Vijay N.,Modani, Sandesh S.,Bhale, Jayant J.,Tathe, Sumangala B.,Pawar, Rajendra P.
experimental part
p. 3898 - 3904
(2009/12/08)

Reusable copper-aluminum hydrotalcite/rac-BINOL system for room temperature selective aerobic oxidation of alcohols
An efficient catalyst system consisting of copper-aluminum hydrotalcite/rac-BINOL ligand has been developed for the oxidation of alcohols using air as a green oxidant at room temperature. Various alcohols could be transformed into their corresponding aldehydes or ketones in good to excellent yields using the set of optimal conditions. This composite catalytic system can also be recovered and reused for several cycles without a significant loss of catalytic activity.
Lakshmi Kantam,Arundhathi,Likhar, Pravin R.,Damodara
supporting information; experimental part
p. 2633 - 2637
(2009/12/30)

Selective debenzylation of aromatic benzyl ethers by silica-supported sodium hydrogen sulfate
A new debenzylation of aromatic benzyl ethers by silica-supported sodium hydrogen sulfate is described. The process proceeds selectively and efficiently in good to excellent yields without affecting sensitive functional groups such as nitro, COOMe, aldehyde, ketone, and tosyl.
Zhou, Linna,Wang, Wenjing,Zuo, Li,Yao, Shanyan,Wang, Wei,Duan, Wenhu
p. 4876 - 4878
(2008/09/21)

A practical palladium catalyzed dehalogenation of aryl halides and α-haloketones
A practical and high-yielding protocol for the dehalogenation of aromatic halides is presented. In the presence of palladium acetate, triphenylphosphine, and potassium carbonate, a number of highly functionalized aromatic halides as well as α-haloketones were dehalogenated with alcohols as hydrogen donors.
Chen, Jingbo,Zhang, Yushun,Yang, Liquan,Zhang, Xiang,Liu, Jianping,Li, Liang,Zhang, Hongbin
p. 4266 - 4270
(2007/10/03)

Vanadium-catalyzed selective aerobic alcohol oxidation in ionic liquid [bmim]PF6
A selective aerobic oxidation of alcohols into the corresponding aldehydes or ketones was developed by using two-component system VO(acac)2/DABCO in the ionic liquid [bmim]PF6, and the catalysts can be recycled and reused for three runs without any significant loss of catalytic activity.
Jiang, Nan,Ragauskas, Arthur J.
p. 273 - 276
(2007/10/03)

Microwave assisted convenient and facile regeneration of carbonyl compounds from semicarbazones, phenylhydrazones and tosylhydrazones using phosphoric acid in solvent-free conditions
Microwave irradiation of semicarbazones, phenylhydrazones and tosylhydrazones of carbonyl compounds with phosphoric acid under solvent-free conditions provides a fast, efficient and simple method for regeneration of carbonyls in excellent yields.
Banerjee, Krishna,Mitra, Alok Kumar,Patra, Amarendra
p. 537 - 539
(2007/10/03)

Solid-supported acids for debenzylation of aryl benzyl ethers
Solid-supported acids have been investigated for aromatic debenzylation reactions. Stoichiometric amounts of solid-supported acids in refluxing toluene with or without 4 equiv of methanol effectively provided the desired aromatic debenzylation products of various systems in moderate to excellent yields (up to 98%).
Petchmanee, Thaninee,Ploypradith, Poonsakdi,Ruchirawat, Somsak
p. 2892 - 2895
(2007/10/03)

A simple method for deprotection of tert-butyldimethylsilyl ethers by using stannous chloride under microwave irradiation
A facile regeneration of hydroxy compounds from their tert- butyldimethylsilyl ethers in presence of stannous chloride under solvent free conditions using domestic microwave oven has been performed efficiently in a short period (5-6 min). The conversion using stannous chloride in ethanol or water for comparison of the efficiency has been described. The generality of the transformation has been confirmed by several examples.
Jadhav, Vinod H.,Borate, Hanumant B.,Wakharkar, Radhika D.
p. 322 - 324
(2007/10/03)

Beckmann rearrangement of ketoximes and deprotection of aldoximes in solvent-free conditions
Phosphoric acid is an efficient and mild reagent for regeneration of aldehyde from oximes, but ketoximes are converted to amides or lactam by Beckmann rearrangement. The reactions are carried out in solvent-free conditions under microwave irradiation.
Banerjee, Krishna,Mitra, Alok Kumar
p. 1876 - 1879
(2007/10/03)

Copper(II)-mediated regeneration of carbonyls from oximes and semicarbazones under solvent-free microwave irradiated conditions
Carbonyl compounds can be regenerated from the corresponding oximes and semicarbazones by a solvent-free, rapid, efficient and simple method under microwave irradiation exploiting copper(II) chloride.
Karchaudhuri, Nilay,De, Aparna,Mitra, Alok Kumar
p. 79 - 81
(2007/10/03)

Palladium charcoal-catalyzed deprotection of O-allylphenols
Allyl aryl ethers can be easily cleaved by the use of 10% Pd/C under mild and basic conditions. The present reaction would involve a SET process rather than a π-allyl-palladium complex. The scope and limitation of this new deprotective methodology is also described.
Ishizaki, Miyuki,Yamada, Makoto,Watanabe, Shin-Ichi,Hoshino, Osamu,Nishitani, Kiyoshi,Hayashida, Maiko,Tanaka, Atsuko,Hara, Hiroshi
p. 7973 - 7981
(2007/10/03)

An eco-friendly regeneration of aldehydes exploiting ammonium acetate under microwave irradiation
A number of bisulphite addition products and diacetates are deprotected separately to the corresponding aldehydes exploiting a green reagent, ammonium acetate in solvent-free conditions under microwave irradiation by a rapid, clean, efficient and high yielding method under environmentally benign conditions.
Mitra, Alok Kumar,Karchaudhuri, Nilay,De, Aparna
p. 237 - 239
(2007/10/03)

Studies on flavans. III. The total synthesis of (±)-7,4′ -dihydroxy-3′-methoxyflavan, (±)-7,3′-dihydroxy-4′ -methoxyflavan, and (±)-7,4′-dihdroxyflavan
The first total synthesis of (±)-7,3′-dihydroxy-4′ -methoxyflavan (1) and (±)-7,4′-dihydroxy-3′-methoxyflavan (2), along with the synthesis of (±)-7,4′-dihydroxyflavan (3), three naturally occurring flavans, were described. The key step is the cyclization of 1,3-diaryl-1-propanol by BF3·Et2O.
Xue, Jijun,Zhang, Xianshu,Chen, Xuesong,Zhang, Yingpeng,Li, Ying
p. 3527 - 3536
(2007/10/03)