- Acceleration of acid-catalyzed hydrolysis in a biphasic system by sodium tetracyanocyclopentadienides
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The hydrolysis of tert-butyldimethylsilyl L-menthyl ether (3) in a CH2Cl2-1 M HCl biphasic solvent system was accelerated by the addition of sodium tetracyanocyclopentadienides 1. Particularly, the reaction rate was enhanced using sodium salt 1a-c with a lipophilic substituent on the cyclopentadienide ring. From the results obtained by a triphasic experiment, hydrolysis proceeds via the formation of hydronium ion 2 in the aqueous phase by ion exchange, followed by the transfer of 2 to the CH2Cl2 phase.
- Sakai, Takeo,Bito, Mariko,Itakura, Makoto,Sato, Honami,Mori, Yuji
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- Selective cleavage of allyl ethers
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A simple, one-step method for the selective cleavage of allyl ethers to alcohols has been developed by use of Ti(O-i-Pr)4 and a commercially available Grignard reagent.
- Lee, Jinhwa,Cha, Jin Kun
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- C2-Symmetric sulfur derivatives of 2,2′,3,3′'-tetramethoxybiphenyl
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A practical route to prepare dithioether, thiophene and thiophene S-dioxide derivatives of 2,2′,3,3′-tetramethoxy-1,1′-biphenyl 1 is described. Resolution of 6,6′-bis(methylthio)-3,3′-dimethoxy-[1,1′-biphenyl]-2,2′ -diol 15 was achieved and its absolute configuration was assigned by X-ray analysis of the corresponding phosphorothioamidate diastereomer 18.
- Delogu, Giovanna,Fabbri, Davide,Dettori, Maria Antonietta,Forni, Alessandra,Casalone, Gianluigi
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- Synthesis of new mixed (-)-menthylalkyltin dihydrides. stereoselective reduction of chiral and prochiral ketones
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This paper reports de synthesis of a series of (-)-menthylalkyltin dihydrides, (-)-MenRSnH2 (R = Me, n-Bu, i-Pr, t-Bu, Neophyl), starting from (-)-menthyltrimethyltin. The new (-)-menthylalkyltin dihydrides 12–16 were used in a study on the stereoselective reduction of chiral (-)-menthone under different reaction conditions. Also the results obtained in the reductions of prochiral acetophenone (27) and 2-acetylnaphthalene (28), with (-)-menthylmethyl- (12) and (-)-menthyli-propyltin (14) dihydrides are informed. Some physical properties as well as full 1H-, 13C-, and 119Sn NMR data of the new organotin compounds are informed.
- Terraza, V. Fabricio,Gerbino, Darío C.,Podestá, Julio C.
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- Intramolecular cyclization of (+)-citronellal using supported 12-tungstophosphoric acid on MCM-41
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Supported heteropolyacids (HPAs) have been used as catalysts by fine-tuning their heterogenous and Br?nsted acidic properties. In this work, supported H3PW12O40 (HPW) on MCM-41 was prepared (2-40 wt%) and applied in the intramolecular cyclization of (+)-citronellal. The synthesized materials were characterized by 31P MAS NMR, XRD, FTIR, pyridine gaseous adsorption, low temperature nitrogen adsorption and thermal analysis. The impregnation of 20% HPW on the surface of MCM-41 decreased the characteristic crystallographic reflections of the support, suggesting that HPW modifies the long-range order. The results show that the HPW was deposited preferentially inside the mesopores of the support and affected the acid strength of the supported catalyst. FTIR studies of pyridine adsorption confirmed the presence of Br?nsted and hydrogen bonded acid sites. All synthesized materials were active in the cyclization reaction, but the 20%HPW/MCM-41 sample was the most active. This catalyst showed about 96% conversion and 65% selectivity to the most important stereoisomer (-)-isopulegol, under 1 h reaction. This catalyst was reused four times with a fair degree of deactivation. The decreased activity was attributed to the formation of small agglomerates in the channels of MCM-41.
- Braga, Patricia R.S.,Costa, Andréia A.,De Freitas, Elon F.,Rocha, Rafael O.,De MacEdo, Julio L.,Araujo, Antonio S.,Dias, José A.,Dias, Sílvia C.L.
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- Chromatography-free Pd-catalyzed deprotection of allyl ethers using PS-DEAM as a scavenger of boronic acids and Pd catalyst
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Polystyrene-bound diethanolamine (PS-DEAM) work-up for a newly developed Pd(PPh3)4-catalyzed cleavage of allylic alkyl ethers using phenylboronic acid can effectively release Pd-free parent alcohols. Furthermore, chromatography-free deallylation can be conducted by using vinylboronic anhydride pyridine complex as an allyl scavenger with a catalytic amount of Pd(OAc)2 and 4-(diphenylphosphino)benzoic acid instead of Pd(PPh3)4 to yield the desired products in high purities and yields after removal of volatile byproducts and the phosphine-derived contaminants by evaporation and sequestration through acid-base interaction with PS-DEAM, respectively.
- Tsukamoto, Hirokazu,Suzuki, Takamichi,Sato, Masanori,Kondo, Yoshinori
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- Reactions of selenothioic acid S-esters with trivalent phosphorus compounds: New synthetic methods for α-phosphoryl alkyl sulfides and alkyl selenides
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The reaction of selenothioic acid S-esters 1 with trialkyl phosphites proceeds smoothly with the extrusion of selenium atoms to afford α-phosphoryl sulfides 2 in good to high yields. A similar reaction takes place more easily with dimethyl phenylphosphonite and methyl diphenylphosphinite, although the ketene selenothioacetals 3 are also formed as by-products in increased yields. The use of diselenoic acid esters If and 1g gives α-phosphoryl selenides 2m and 2n. The products exhibit characteristic chemical shifts and coupling constants in their 31P NMR spectra. The structure of α-phosphoryl selenide 2n is confirmed by X-ray molecular structure analysis. The reaction with triphenylphosphine leads to oxidative dimerization of ester 1d to give divinyl diselenide 4 in good yield. A catalytic amount of triphenylphosphine is also effective to form divinyl diselenide 4. The reaction may begin with the nucleophilic attack of triphenylphosphine on the carbon atom of the selenocarbonyl group of ester 1d. Details of the reaction pathway leading to α-phosphoryl sulfides 2 are also discussed. The reaction with menthyl diphenylphosphinite 12 has suggested that the reaction may proceed via initial nucleophilic attack of trivalent phosphorus compounds bearing alkoxy groups on the selenium atom of esters 1. The intermediacy of phosphonium ylide 14 has also been supported by the reaction of the ester 1h which gives 1,4-oxathiane 15.
- Murai, Toshiaki,Izumi, Chiyoko,Itoh, Toshihide,Kato, Shinzi
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- A thermostable variant of Bacillus subtilis esterase: Characterization and application for resolving dl-menthyl acetate
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Bacillus subtilis esterase (BSE) exhibits high activity, extraordinary substrate/product tolerance and excellent enantioselectivity in the production of l-menthol through enantioselective hydrolysis of dl-menthyl acetate. However, rapid inactivation of wild-type BSE at elevated temperatures often hampers its applications. In this work, directed evolution was used to create thermostable mutants of BSE. After screening and recombination of beneficial mutations, BSEV4 was chose for the best mutant. The BSEV4 had half-lives of 462, 248 and 0.34 h at 30, 40 and 50 °C, respectively, which were 5.6, 4.1 and 2.0 folds longer than those of BSEWT. Moreover, BSEV4 showed an increase of 4.5 °C in T5015 and a higher temperature optimum compared with the wild-type enzyme. In the kinetic resolution of dl-menthyl acetate at 1.0 M substrate loading, BSEV4 displayed improvements in operational stability than BSEWT, leading to a 1.5-fold higher total turnover number at 45 °C. The model structure of BSEV4 with four mutations, built with a highly homologous p-nitrobenzyl esterase (PDB ID: 1QE3) as the template, revealed that the newly formed hydrogen bonds and ionic bonds were beneficial for enhancing the thermostability of BSE.
- Gong, Yi,Xu, Guo-Chao,Zheng, Gao-Wei,Li, Chun-Xiu,Xu, Jian-He
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- TRANSFORMATION OF ISOPRENOIDS BY ORCHIDS IN TISSUE CULTURE
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Key Word Index - Epidendrum ochraceum; Cymbidium 'Saint Pierre'; Dendrobium phalaenopsis; Orchidaceae; orchids; tissue culture; biotransformations; testosterone; androsterolone; menthyl acetate. Tissue cultures of Epidendrum ochraceum, Cymbidium 'Saint Pierre' and Dendrobium phalaenopsis were found to transform some isoprenoids.The transformation of the oxygen functions at C-17 in androstane derivatives and the hydrolysis of (+/-)-menthyl acetate were investigated in some detail.The degree of hydrolysis of the latter was about 75-85 percent.
- Mironowicz, Agnieszka,Kukulczanka, Krystyna,Krasinski, Krzysztof,Siewinski, Antoni
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- A novel benzoyl-type fluorous protecting group for use in fluorous synthesis
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TfBz-OH, a novel benzoyl-type fluorous protecting reagent, has been easily prepared. It was found that the TfBz (trisfluorous chain-type benzoyl) group can be successfully introduced onto a hydroxyl function, removed in high yield, and recycled after deprotection. The use of the TfBz group makes it possible to synthesize an oligosaccharide by minimal column chromatography purification, because each synthetic intermediate is easily purified simply by fluorous-organic solvent extraction.
- Miura, Tsuyoshi,Satoh, Ai,Goto, Kohtaro,Murakami, Yasuoki,Imai, Nobuyuki,Inazu, Toshiyuki
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- Facile oxidation of benzyl ethers by the 2-nitrobenzene-sulfonylperoxyl intermediate generated from 2-nitrobenzenesulfonyl chloride and superoxide
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Various benzyl ethers react with a 2-nitrobenzenesulfonyl-peroxyl radical intermediate generated from 2-nitrobenzenesulfonyl chloride and potassium superoxide at -25°C in acetonitrile to give the corresponding esters in high yields.
- Kim, Yong Hae,Kim, Yong Il,Kim, Joong Young
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- Chiral pyridinium-based ionic liquids containing the (1R,2S,5R)-(-)-menthyl group
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A novel class of chiral pyridinium salts in which the chirality resides in the cation have been prepared and characterized. The physicochemical and anti-microbial properties have been determined. The group of prepared salts contained chiral ionic liquids and decomposable chiral pyridinium chlorides.
- Pernak, Juliusz,Feder-Kubis, Joanna
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- Novel highly efficient absolute optical resolution method by serial combination of two asymmetric reactions from acetylene monomers having racemic substituents
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For general optical resolution, an optical resolution agent is necessary, and the best agent should be selected for each racemic compound. In this study, we will report that a novel optical resolution method by circularly polarized light (CPL) without any
- Aoki, Toshiki,Kaneko, Takashi,Liu, Lijia,Suzuki, Junpei,Tang, Yanan,Teraguchi, Masahiro
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supporting information
p. 450 - 461
(2022/01/15)
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- Continuous synthesis of menthol from citronellal and citral over Ni-beta-zeolite-sepiolite composite catalyst
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One-pot continuous synthesis of menthols both from citronellal and citral was investigated over 5 wt% Ni supported on H-Beta-38-sepiolite composite catalyst at 60–70 °C under 10–29 bar hydrogen pressure. A relatively high menthols yield of 53% and 49% and stereoselectivity to menthol of 71–76% and 72–74% were obtained from citronellal and citral respectively at the contact time 4.2 min, 70 °C and 20 bar. Citral conversion noticeably decreased with time-on-stream under 10 and 15 bar of hydrogen pressure accompanied by accumulation of citronellal, the primary hydrogenation product of citral, practically not affecting selectivity to menthol. A substantial amount of defuctionalization products observed during citral conversion, especially at the beginning of the reaction (ca. 1 h), indicated that all intermediates could contribute to formation of menthanes. Ni/H-Beta-38-sepiolite composite material prepared by extrusion was characterized by TEM, SEM, XPS, XRD, ICP-OES, N2 physisorption and FTIR techniques to perceive the interrelation between the physico-chemical and catalytic properties.
- Er?nen, Kari,M?ki-Arvela, P?ivi,Martinez-Klimov, Mark,Muller, Joseph,Murzin, Dmitry Yu.,Peurla, Markus,Simakova, Irina,Vajglova, Zuzana
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- Preparation method of yellowing-resistant L-menthol
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The invention provides a preparation method of yellowing-resistant L-menthol, wherein the preparation method of the yellowing-resistant L-menthol comprises the steps: in the presence of a hydrogenation catalyst, carrying out hydrogenation reaction on a raw material to generate the yellowing-resistant L-menthol, wherein the hydrogenation catalyst is a skeleton nickel catalyst, the raw material is L-isopulegol, and the anisidine value in the raw material for the hydrogenation reaction is controlled to be less than or equal to 10 mmol/kg and/or the peroxide value in the raw material for the hydrogenation reaction is controlled to be less than or equal to 5 mmol/kg. By adopting the preparation method disclosed by the invention, the yellowing resistance of the L-menthol can be remarkably improved.
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Paragraph 0066-0095
(2021/02/06)
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- Nickel-catalyzed reductive deoxygenation of diverse C-O bond-bearing functional groups
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We report a catalytic method for the direct deoxygenation of various C-O bond-containing functional groups. Using a Ni(II) pre-catalyst and silane reducing agent, alcohols, epoxides, and ethers are reduced to the corresponding alkane. Unsaturated species including aldehydes and ketones are also deoxygenated via initial formation of an intermediate silylated alcohol. The reaction is chemoselective for C(sp3)-O bonds, leaving amines, anilines, aryl ethers, alkenes, and nitrogen-containing heterocycles untouched. Applications toward catalytic deuteration, benzyl ether deprotection, and the valorization of biomass-derived feedstocks demonstrate some of the practical aspects of this methodology.
- Cook, Adam,MacLean, Haydn,St. Onge, Piers,Newman, Stephen G.
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p. 13337 - 13347
(2021/11/20)
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- A Bifunctional Copper Catalyst Enables Ester Reduction with H2: Expanding the Reactivity Space of Nucleophilic Copper Hydrides
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Employing a bifunctional catalyst based on a copper(I)/NHC complex and a guanidine organocatalyst, catalytic ester reductions to alcohols with H2 as terminal reducing agent are facilitated. The approach taken here enables the simultaneous activation of esters through hydrogen bonding and formation of nucleophilic copper(I) hydrides from H2, resulting in a catalytic hydride transfer to esters. The reduction step is further facilitated by a proton shuttle mediated by the guanidinium subunit. This bifunctional approach to ester reductions for the first time shifts the reactivity of generally considered "soft"copper(I) hydrides to previously unreactive "hard"ester electrophiles and paves the way for a replacement of stoichiometric reducing agents by a catalyst and H2.
- Kaicharla, Trinadh,Ngoc, Trung Tran,Teichert, Johannes F.,Tzaras, Dimitrios-Ioannis,Zimmermann, Birte M.
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supporting information
p. 16865 - 16873
(2021/10/20)
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- Nickel Hydride Catalyzed Cleavage of Allyl Ethers Induced by Isomerization
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This report discloses the deallylation of O - and N -allyl functional groups by using a combination of a Ni-H precatalyst and excess Bronsted acid. Key steps are the isomerization of the O - or N -allyl group through Ni-catalyzed double-bond migration followed by Bronsted acid induced O/N-C bond hydrolysis. A variety of functional groups are tolerated in this protocol, highlighting its synthetic value.
- Kathe, Prasad M.,Berkefeld, Andreas,Fleischer, Ivana
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supporting information
p. 1629 - 1632
(2021/02/09)
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- Me3SI-promoted chemoselective deacetylation: a general and mild protocol
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A Me3SI-mediated simple and efficient protocol for the chemoselective deprotection of acetyl groups has been developedviaemploying KMnO4as an additive. This chemoselective deacetylation is amenable to a wide range of substrates, tolerating diverse and sensitive functional groups in carbohydrates, amino acids, natural products, heterocycles, and general scaffolds. The protocol is attractive because it uses an environmentally benign reagent system to perform quantitative and clean transformations under ambient conditions.
- Gurawa, Aakanksha,Kashyap, Sudhir,Kumar, Manoj
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p. 19310 - 19315
(2021/06/03)
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- Preparation of Neutral trans - Cis [Ru(O2CR)2P2(NN)], Cationic [Ru(O2CR)P2(NN)](O2CR) and Pincer [Ru(O2CR)(CNN)P2] (P = PPh3, P2= diphosphine) Carboxylate Complexes and their Application in the Catalytic Carbonyl Compounds Reduction
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The diacetate complexes trans-[Ru(κ1-OAc)2(PPh3)2(NN)] (NN = ethylenediamine (en) (1), 2-(aminomethyl)pyridine (ampy) (2), 2-(aminomethyl)pyrimidine (ampyrim) (3)) have been isolated in 76-88% yield by reaction of [Ru(κ2-OAc)2(PPh3)2] with the corresponding nitrogen ligands. The ampy-type derivatives 2 and 3 undergo isomerization to the thermodynamically most stable cationic complexes [Ru(κ1-OAc)(PPh3)2(NN)]OAc (2a and 3a) and cis-[Ru(κ1-OAc)2(PPh3)2(NN)] (2b and 3b) in methanol at RT. The trans-[Ru(κ1-OAc)2(P2)2] (P2 = dppm (4), dppe (5)) compounds have been synthesized from [Ru(κ2-OAc)2(PPh3)2] by reaction with the suitable diphosphine in toluene at 95 °C. The complex cis-[Ru(κ1-OAc)2(dppm)(ampy)](6) has been obtained from [Ru(κ2-OAc)2(PPh3)2] and dppm in toluene at reflux and reaction with ampy. The derivatives trans-[Ru(κ1-OAc)2P2(NN)] (7-16; NN = en, ampy, ampyrim, 8-aminoquinoline; P2 = dppp, dppb, dppf, (R)-BINAP) can be easily synthesized from [Ru(κ2-OAc)2(PPh3)2] with a diphosphine and treatment with the NN ligands at RT. Alternatively these compounds have been prepared from trans-[Ru(OAc)2(PPh3)2(NN)] by reaction with the diphosphine in MEK at 50 °C. The use of (R)-BINAP affords trans-[Ru(κ1-OAc)2((R)-BINAP)(NN)] (NN = ampy (11), ampyrim (15)) isolated as single stereoisomers. Treatment of the ampy-type complexes 8-15 with methanol at RT leads to isomerization to the cationic derivatives [Ru(κ2-OAc)P2(NN)]OAc (8a-15a; NN = ampy, ampyrim; P2 = dppp, dppb, dppf, (R)-BINAP). Similarly to 2, the dipivalate trans-[Ru(κ1-OPiv)2(PPh3)2(ampy)] (18) is prepared from [Ru(κ2-OPiv)2(PPh3)2] (17) and ampy in CHCl3. The pincer acetate [Ru(κ1-OAc)(CNNOMe)(PPh3)2] (19) has been synthesized from [Ru(κ2-OAc)2(PPh3)2] and HCNNOMe ligand in 2-propanol with NEt3 at reflux. In addition, the dppb pincer complexes [Ru(κ1-OAc)(CNN)(dppb)] (CNN = AMTP (20), AMBQPh (21)) have been obtained from [Ru(κ2-OAc)2(PPh3)2], dppb, and HAMTP or HAMBQPh with NEt3, respectively. The acetate NN and pincer complexes are active in transfer hydrogenation with 2-propanol and hydrogenation with H2 of carbonyl compounds at S/C values of up to 10000 and with TOF values of up to 160000 h-1.
- Baldino, Salvatore,Giboulot, Steven,Lovison, Denise,Nedden, Hans Günter,P?thig, Alexander,Zanotti-Gerosa, Antonio,Zuccaccia, Daniele,Ballico, Maurizio,Baratta, Walter
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p. 1086 - 1103
(2021/05/06)
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- Well-defined Cp*Co(III)-catalyzed Hydrogenation of Carbonates and Polycarbonates
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We herein report the catalytic hydrogenation of carbonates and polycarbonates into their corresponding diols/alcohols using well-defined, air-stable, high-valent cobalt complexes. Several novel Cp*Co(III) complexes bearing N,O-chelation were isolated for the first time and structurally characterized by various spectroscopic techniques including single crystal X-ray crystallography. These novel Co(III) complexes have shown excellent catalytic activity to produce value added diols/alcohols from carbonate and polycarbonates through hydrogenation using molecular hydrogen as sole reductant or iPrOH as transfer hydrogenation source. To demonstrate the developed methodology's practical applicability, we have recycled the bisphenol A monomer from compact disc (CD) through hydrogenation under the established reaction conditions using phosphine-free, earth-abundant, air- and moisture-stable high-valent cobalt catalysts.
- Dahiya, Pardeep,Gangwar, Manoj Kumar,Sundararaju, Basker
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p. 934 - 939
(2020/12/15)
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- Method for preparing L-menthol by adopting modified homogeneous catalyst
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The invention discloses a method for preparing L-menthol by adopting a modified homogeneous catalyst. The method comprises the following steps: preparing a modified homogeneous catalyst, preparing isopulegol, preparing D, L-menthol, and preparing L-menthol; wherein a ligand is prepared from 2, 6-dimethylpyridine and a ketone compound by using the modified homogeneous catalyst, the ligand is reacted with alkyl aluminum to obtain an organic aluminum compound, and L-menthol is prepared by chemically inducing chiral resolution of D, L-menthol. According to the method, the organic aluminum compoundis used as the catalyst of the ring-closure reaction of citronellal, so that the yield of isopulegol is increased, the selectivity on product isopulegol is high, and the used organic aluminum catalyst is easy to synthesize, high in stereoselectivity to reaction and easy to crystallize and recover; D, L-menthol is split by a chemical induction method, the method is simple to operate, the reactionyield of each step is high, the reaction conditions are stable, the product cannot be partially racemized, and the product loss is small.
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- Scrap waste automotive converters as efficient catalysts for the continuous-flow hydrogenations of biomass derived chemicals
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The catalytic activity of scrap ceramic-cores of automotive catalytic converters (SCATs) was investigated in the continuous-flow hydrogenation of different biomass-derived chemicals. The waste SCAT powders were deeply characterized by ICP-MS, TGA, MP-AES, XRD, N2 physisorption, TPR, HRTEM and EDS before and after utilization as a catalyst. The hydrogenation reactions of isopulegol to menthol, cinnamyl alcohol to hydrocinnamyl alcohol, isoeugenol to dihydroeugenol, vanillin to vanillyl alcohol and benzaldehyde to benzyl alcohol were performed studying the influence of various reaction parameters (temperature, pressure, flow rate and concentration of the starting material) on the final yields. The outstanding performance and stability obtained for the low metal content of waste-derived catalysts can be attributed to the co-presence of different noble metals as well as to the composite structure itself.
- Cova, Camilla Maria,Zuliani, Alessio,Manno, Roberta,Sebastian, Victor,Luque, Rafael
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p. 1414 - 1423
(2020/03/11)
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- Chemoselective Oxidation of p-Methoxybenzyl Ethers by an Electronically Tuned Nitroxyl Radical Catalyst
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The oxidation of p-methoxy benzyl (PMB) ethers was achieved using nitroxyl radical catalyst 1, which contains electron-withdrawing ester groups adjacent to the nitroxyl group. The oxidative deprotection of the PMB moieties on the hydroxy groups was observed upon treatment of 1 with 1 equiv of the co-oxidant phenyl iodonium bis(trifluoroacetate) (PIFA). The corresponding carbonyl compounds were obtained by treating the PMB-protected alcohols with 1 and an excess of PIFA.
- Hamada, Shohei,Sugimoto, Koichi,Elboray, Elghareeb E.,Kawabata, Takeo,Furuta, Takumi
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supporting information
p. 5486 - 5490
(2020/07/24)
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- KMnO4-catalyzed chemoselective deprotection of acetate and controllable deacetylation-oxidation in one pot
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A novel and efficient protocol for chemoselective deacetylation under ambient conditions was developed using catalytic KMnO4. The stoichiometric use of KMnO4 highlighted the dual role of a heterogeneous oxidant enabling direct access to aromatic aldehydes in one-pot sequential deacetylation-oxidation. The reaction employed an alternative solvent system and allowed the clean transformation of benzyl acetate to sensitive aldehyde in a single step while preventing over-oxidation to acids. Use of inexpensive and readily accessible KMnO4 as an environmentally benign reagent and the ease of the reaction operation were particularly attractive, and enabled the controlled oxidation and facile cleavage of acetate in a preceding step. This journal is
- Gurawa, Aakanksha,Kumar, Manoj,Rao, Dodla S.,Kashyap, Sudhir
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supporting information
p. 16702 - 16707
(2020/10/27)
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- Continuous flow synthesis of menthol: Via tandem cyclisation-hydrogenation of citronellal catalysed by scrap catalytic converters
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A continuous flow synthesis of menthol starting from citronellal catalysed by scrap catalytic converters is reported. The reaction was conducted in a tandem system connecting in series two catalytic systems, with the first having Lewis acid properties (favouring the cyclisation of citronellal to isopulegols) and the second having hydrogenation catalytic activity (catalysing the hydrogenation of isopulegols to menthols). A Lewis acid catalyst was prepared by supporting iron oxide nanoparticles over a waste material, i.e. the ceramic core of scrap catalytic converters (SCATs) via a microwave assisted method. Most importantly, SCATs, containing a low residual noble metal content, could be directly employed in the second step as hydrogenation catalysts. The reaction was performed studying the influence on the yield and selectivity to (-)-menthol of various reaction parameters (T, p and flow rate). Under the best reaction conditions (at a flow rate of 0.1 mL min-1 and at 373 K and 413 K for cyclisation and hydrogenation steps respectively) a conversion of >99% of (+)-citronellal to (-)-menthol with 77% final yield was achieved.
- Zuliani, Alessio,Cova, Camilla Maria,Manno, Roberta,Sebastian, Victor,Romero, Antonio A.,Luque, Rafael
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p. 379 - 387
(2020/02/13)
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- Method for preparation of L-menthone from R-citronellal
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The invention discloses a method for preparation of L-menthone from R-citronellal. In the presence of a Ru-Cu-MOF catalyst, R-citronellal is cyclized to prepare L-menthone, the reaction conditions aremild, the reaction enantioselectivity is 90%-99.5%, the conversion rate can reach 95%-99.9%, and the ee value of menthone can reach 90%-99.9%.
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Paragraph 0094; 0095
(2020/04/02)
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- Chemoselective Oxidation of Equatorial Alcohols with N-Ligated λ3-Iodanes
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The site-selective and chemoselective functionalization of alcohols in complex polyols remains a formidable synthetic challenge. Whereas significant advancements have been made in selective derivatization at the oxygen center, chemoselective oxidation to the corresponding carbonyls is less developed. In cyclic systems, whereas the selective oxidation of axial alcohols is well known, a complementary equatorial selective process has not yet been reported. Herein we report the utility of nitrogen-ligated (bis)cationic λ3-iodanes (N-HVIs) for alcohol oxidation and their unprecedented levels of selectivity for the oxidation of equatorial over axial alcohols. The conditions are mild, and the simple pyridine-ligated reagent (Py-HVI) is readily synthesized from commercial PhI(OAc)2 and can be either isolated or generated in situ. Conformational selectivity is demonstrated in both flexible 1,2-substituted cyclohexanols and rigid polyol scaffolds, providing chemists with a novel tool for chemoselective oxidation.
- Mikhael, Myriam,Adler, Sophia A.,Wengryniuk, Sarah E.
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supporting information
p. 5889 - 5893
(2019/08/26)
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- Oxidative Deprotection of p-Methoxybenzyl Ethers via Metal-Free Photoredox Catalysis
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An efficient and greener deprotection method for p-methoxybenzyl (PMB) ethers using a metal-free visible light photoredox catalyst and air and ammonium persulfate as the terminal oxidants is presented. Various functional groups and protecting groups were tolerated in the developed method to achieve good to excellent yields in short reaction times. Significantly, the developed method was compatible with PMB ethers derived from primary, secondary, and tertiary alcohols and a gram-scale reaction. Mechanistic studies support a proposed reaction mechanism that involves single electron oxidation of the PMB ether.
- Ahn, Deok Kyun,Kang, Young Woo,Woo, Sang Kook
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p. 3612 - 3623
(2019/03/11)
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- Hafnium Triflate as a Highly Potent Catalyst for Regio- and Chemoselective Deprotection of Silyl Ethers
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As a Group IVB transition metal Lewis acid, hafnium triflate [Hf(OTf) 4 ] exhibited exceptionally high potency in desilylations. Since the amounts of Hf(OTf) 4 required for the deprotection of 1°, 2°, 3° alkyl and aryl tert -butyldimethylsilyl (TBS) ethers are significantly different, ranging from 0.05 mol% to 3 mol%, regioselective deprotection of TBS could be easily implemented. Moreover, chemoselective cleavage of different silyl ethers or removal of TBS in the presence of most hydroxyl protecting groups was also accomplished. NMR analyses of silyl products from TBS deprotection indicated that Hf(OTf) 4 -catalyzed desilylation may proceed via different mechanisms, depending on the solvent used.
- Zheng, Xiu-An,Kong, Rui,Huang, Hua-Shan,Wei, Jing-Ying,Chen, Ji-Zong,Gong, Shan-Shan,Sun, Qi
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supporting information
p. 944 - 953
(2019/02/10)
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- Hafnium trifluoromethanesulfonate catalyzed silyl ether protecting group removing method
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The invention provides a hafnium trifluoromethanesulfonate catalyzed silyl ether protecting group removing method. Various silyl ether protecting groups of nearly 50 kinds of substrates can be efficiently removed in 0.5-16 hours at room temperature by taking 0.02mol%-0.3mol% hafnium trifluoromethanesulfonate as a catalyst, a silyl ether protected hydroxyl compound as a substrate and conventional AR methanol as a solvent. 42 kinds of silyl ether protecting group removing products can be obtained at high yield by performing conventional slica column chromatography purification on a crude product. By regulating the use amount of the catalyst, the Hf(OTf)4 catalyst can realize regioselective removal of 1-degree, 2-degree and 3-degree alkyl TBS and aryl TBS protective groups. Moreover, in a proper equivalent scope, the Hf(OTf)4 catalyst can also realize 1) chemoselective removal of different kinds of silica-based protective groups; and 2) chemoselective removal of 1-degree TBS protective groups under the condition of not affecting a majority of common hydroxyl protective groups.
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Paragraph 0017; 0018
(2019/01/21)
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- Catalytic removal of tert-butyldimethylsilyl (TBS) ether by PVP-I
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A mild, efficient and rapid protocol the deprotection of alcoholic TBDMS ethers using PVP-1 as catalyst in methanol, the procedure of deprotection of various TBDMS ethers were found to be very convenient, easy work-up, high yielding.
- Ke, Yanxiong,Lu, Guangying,Ren, Jiangmeng,Wang, Di,Zeng, Bu-Bing
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- Flat and Efficient H CNN and CNN Pincer Ruthenium Catalysts for Carbonyl Compound Reduction
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The bidentate HCNN dicarbonyl ruthenium complexes trans,cis-[RuCl2(HCNN)(CO)2] (1-3) and trans,cis-[RuCl2(ampy)(CO)2] (1a) were prepared by reaction of [RuCl2(CO)2]n with 1-[6-(4′-methylphenyl)pyridin-2-yl]methanamine, benzo[h]quinoline (HCNN), and 2-(aminomethyl)pyridine (ampy) ligands. Alternatively, the derivatives 1-3 were obtained from the reaction of RuCl3 hydrate with HCO2H and HCNN. The pincer CNN cis-[RuCl(CNN)(CO)2] (4) was isolated from 1 by reaction with NEt3. The monocarbonyl complexes trans-[RuCl2(HCNN)(PPh3)(CO)] (5-7) were synthesized from [RuCl2(dmf)(PPh3)2(CO)] and HCNN ligands, while the diacetate trans-[Ru(OAc)2(HCNN)(PPh3)(CO)] (8) was obtained from [Ru(OAc)2(PPh3)2(CO)]. Carbonylation of cis-[RuCl(CNN)(PPh3)2] with CO afforded the pincer derivatives [RuCl(CNN)(PPh3)(CO)] (9-11). Treatment of 9 with Na[BArf]4 and PPh3 gave the cationic complex trans-[Ru(CNN)(PPh3)2(CO)][BArf4] (12). The dicarbonyl derivatives 1-4, in the presence of PPh3 or PCy3, and the monocarbonyl complexes 5-12 catalyzed the transfer hydrogenation (TH) of acetophenone (a) in 2-propanol at reflux (S/C = 1000-100000 and TOF up to 100000 h-1). Compounds 1-3, with PCy3, and 6 and 8-10 were proven to catalyze the TH of carbonyl compounds, including α,β-unsaturated aldehydes and bulky ketones (S/C and TOF up to 10000 and 100000 h-1, respectively). The derivatives 1-3 with PCy3 and 5 and 6 catalyzed the hydrogenation (HY) of a (H2, 30 bar) at 70 °C (S/C = 2000-10000). Complex 5 was active in the HY of diaryl ketones and aryl methyl ketones, leading to complete conversion at S/C = 10000.
- Giboulot, Steven,Baldino, Salvatore,Ballico, Maurizio,Figliolia, Rosario,P?thig, Alexander,Zhang, Shuanming,Zuccaccia, Daniele,Baratta, Walter
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p. 1127 - 1142
(2019/03/14)
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- P-Methylbenzyl Group: Oxidative Removal and Orthogonal Alcohol Deprotection
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We describe the practical removal of p-methylbenzyl (MBn) protections of alcohols by treatment with 2,3-dichloro-5,6-dicyano-p-benzoquinone. When a molecule bears benzyl and MBn groups, the oxidant selectively removes the latter groups. Further, the MBn groups tolerate ceric ammonium nitrate, resulting in chemoselective removal of the p-methoxybenzyl group in the presence of the MBn groups. These orthogonal alcohol deprotections would provide novel synthetic strategies of organic compounds.
- Ikeuchi, Kazutada,Murasawa, Kentaro,Ohara, Kenya,Yamada, Hidetoshi
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supporting information
p. 6638 - 6642
(2019/09/30)
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- One-Pot Absolute Stereochemical Identification of Alcohols via Guanidinium Sulfate Crystallization
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A novel technique for the absolute stereochemical determination of alcohols has been developed that uses crystallization of guanidinium salts of organosulfates. The simple one-pot, two-step process leverages facile formation of guandinium organosulfate single crystals for the straightforward determination of the absolute stereochemistry of enantiopure alcohols by means of X-ray crystallography. The strong hydrogen bonding network drives the stability of the crystal lattice and allows for a diverse range of organic alcohol substrates to be analyzed.
- Brummel, Beau R.,Lee, Kinsey G.,McMillen, Colin D.,Kolis, Joseph W.,Whitehead, Daniel C.
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supporting information
p. 9622 - 9627
(2019/12/02)
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- Engineering the "missing Link" in Biosynthetic (-)-Menthol Production: Bacterial Isopulegone Isomerase
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The realization of a synthetic biology approach to microbial (1R,2S,5R)-(-)-menthol (1) production relies on the identification of a gene encoding an isopulegone isomerase (IPGI), the only enzyme in the Mentha piperita biosynthetic pathway as yet unidentified. We demonstrate that Δ5-3-ketosteroid isomerase (KSI) from Pseudomonas putida can act as an IPGI, producing (R)-(+)-pulegone ((R)-2) from (+)-cis-isopulegone (3). Using a robotics-driven semirational design strategy, we identified a key KSI variant encoding four active site mutations, which confer a 4.3-fold increase in activity over the wild-type enzyme. This was assisted by the generation of crystal structures of four KSI variants, combined with molecular modeling of 3 binding to identify key active site residue targets. The KSI variant was demonstrated to function efficiently within cascade biocatalytic reactions with downstream Mentha enzymes pulegone reductase and (-)-menthone:(-)-menthol reductase to generate 1 from 3. This study introduces the use of a recombinant IPGI, engineered to function efficiently within a biosynthetic pathway for the production of 1 in microorganisms.
- Currin, Andrew,Dunstan, Mark S.,Johannissen, Linus O.,Hollywood, Katherine A.,Vinaixa, Maria,Jervis, Adrian J.,Swainston, Neil,Rattray, Nicholas J. W.,Gardiner, John M.,Kell, Douglas B.,Takano, Eriko,Toogood, Helen S.,Scrutton, Nigel S.
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p. 2012 - 2020
(2018/03/13)
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- Hydrogen Sulfide: A Reagent for pH-Driven Bioinspired 1,2-Diol Mono-deoxygenation and Carbonyl Reduction in Water
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Hydrogen sulfide (H2S) was evaluated for its peculiar sulfur radical species generated at different pHs and was used under photolytical conditions in aqueous medium for the reduction of 1,2-diols to alcohols. The conversion steps of 1,2-cyclopentanediol to cyclopentanol via cyclopentanone were analyzed, and it was proven that the reaction proceeds via a dual catalytic/radical chain mechanism. This approach was successfully adapted to the reduction of a variety of carbonyl compounds using H2S at pH 9 in water. This work opens up the field of environmental friendly synthetic processes using the pH-driven modulation of reactivity of this simple reagent in water.
- Barata-Vallejo, Sebastián,Ferreri, Carla,Golding, Bernard T.,Chatgilialoglu, Chryssostomos
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supporting information
p. 4290 - 4294
(2018/07/29)
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- Production of l-menthyl acetate through kinetic resolution by?Candida cylindracea lipase: effects of alkaloids as additives
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Abstract: Enzymatic transesterification of dl-menthol with vinyl acetate in tert-Butyl methyl ether (TBME) catalyzed by Candida cylindracea lipase (CCL) was carried out in the presence of cinchona alkaloid as additive. The effects of various reaction parameters, such as lipase nature and loading, acylating agent, molecular sieves, solvents and various additives, on the reactivity as well as on the enantioselectivity were investigated. A significant improvement of CCL reactivity has been recorded after using cinchona alkaloid as additive in TBME. A high enantiomeric ratio (E = 80) was achieved when 30?mol% of quinidine was added, and l-(-)-menthyl acetate was obtained with 93% optical purity and 49% conversion. This process was easily applied to gram-scale quantities, using commercially inexpensive lipase, providing high yield optically active menthol under mild experimental conditions. Graphical abstract: [Figure not available: see fulltext.].
- Belkacemi, Fatima Zohra,Merabet-Khelassi, Mounia,Aribi-Zouioueche, Louisa,Riant, Olivier
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p. 6847 - 6860
(2018/07/15)
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- BORYL ETHERS, CARBONATES, AND CYCLIC ACETALS AS OXIDATIVELY-TRIGGERED DRUG DELIVERY VEHICLES
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A compound, or a pharmaceutically acceptable salt thereof, having a structure of Formula (I), wherein L is a cleavable linker group; X is a cargo moiety-containing group; and R1 and R2 are each independently hydrogen, alkyl, or substituted alkyl; or R1 and R2 together form a boronic ester ring or a substituted boronic ester group.
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Page/Page column 27; 28
(2018/03/28)
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- Heterogeneous acidic catalysts for the tetrahydropyranylation of alcohols and phenols in green ethereal solvents
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The application of heterogeneous catalysis and green solvents to the set up of widely employed reactions is a challenge in contemporary organic chemistry. We applied such an approach to the synthesis and further conversion of tetrahydropyranyl ethers, an important class of compounds widely employed in multistep syntheses. Several alcohols and phenols were almost quantitatively converted into the corresponding tetrahydropyranyl ethers in cyclopentyl methyl ether or 2-methyltetrahydrofuran employing NH4HSO4 supported on SiO2 as a recyclable acidic catalyst. Easy work up of the reaction mixtures and the versatility of the solvents allowed further conversion of the reaction products under one-pot reaction conditions.
- Azzena, Ugo,Carraro, Massimo,Modugno, Gloria,Pisano, Luisa,Urtis, Luigi
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supporting information
p. 1655 - 1659
(2018/07/25)
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- Application of Silicon-Initiated Water Splitting for the Reduction of Organic Substrates
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The use of water as a donor for hydrogen suitable for the reduction of several important classes of organic compounds is described. It is found that the reductive water splitting can be promoted by several metalloids among which silicon shows the best efficiency. The developed methodologies were applied for the reduction of nitro compounds, N-oxides, sulfoxides, alkenes, alkynes, hydrodehalogenation as well as for the gram-scale synthesis of several substrates of industrial importance.
- Gevorgyan, Ashot,Mkrtchyan, Satenik,Grigoryan, Tatevik,Iaroshenko, Viktor O.
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p. 375 - 382
(2018/06/04)
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- Reliably Regioselective Dialkyl Ether Cleavage with Mixed Boron Trihalides
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A protocol for the regioselective cleavage of unsymmetrical alkyl ethers to generate alkyl alcohol and alkyl bromide products is described. A mixture of trihaloboranes triggers this conversion and exhibits improved reactivity profiles (regioselectivity and yield) compared with BBr3 alone. Additionally, this procedure allows the efficient synthesis of (B-Cl) dialkyl boronate esters. There are limited methods to generate acyclic dialkoxyboryl chlorides, and these intermediates constitute important synthons in main-group chemistry.
- Atienza, Bren Jordan P.,Truong, Nam,Williams, Florence J.
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p. 6332 - 6335
(2018/10/09)
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- Inexpensive Ruthenium NNS-Complexes as Efficient Ester Hydrogenation Catalysts with High C=O vs. C=C Selectivities
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Ru(NNS)(PPh3)Cl2 (NNS=2-(methylthio)-N-(pyridin-2-yl-methyl)ethan-1-amine) was employed in the hydrogenation of α,β-unsaturated esters, reaching selectivities for the allylic alcohol up to 95% in the hydrogenation of iso-butylcinnamate. In addition, several ester substrates were hydrogenated with catalyst loadings as low as 0.05?mol%. Surprisingly, selectivity of the hydrogenation of the C=O vs the C=C bonds strongly depends on the solvent. (Figure presented.).
- Stadler, Bernhard M.,Puylaert, Pim,Diekamp, Justus,van Heck, Richard,Fan, Yuting,Spannenberg, Anke,Hinze, Sandra,de Vries, Johannes G.
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supporting information
p. 1151 - 1158
(2018/02/06)
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- Mild alkaline hydrolysis of hindered esters in non-aqueous solution
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Sterically hindered esters of carboxylic acids, which are considered very resistant to saponification, were rapidly and efficiently saponified in a non-aqueous medium using NaOH in MeOH/CH2Cl2 (1:9) at room temperature. Furthermore, this reaction protocol was extended and successfully applied to the hydrolysis of tosylates and N-tosyl indoles.
- Theodorou, Vassiliki,Alagiannis, Michalis,Ntemou, Nikoleta,Brentas, Alexios,Voulgari, Pinelopi,Polychronidou, Vasiliki,Gogou, Marina,Giannelos, Marios,Skobridis, Konstantinos
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p. 308 - 319
(2018/11/26)
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- Cobalt Pincer Complexes for Catalytic Reduction of Carboxylic Acid Esters
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A selection of cobalt(I) and cobalt(II) pincer type complexes with different substitution patterns was tested in the catalytic reduction of carboxylic acid esters to alcohols. The cobalt pincer type complex 4 is suitable for the hydrogenation of aromatic as well as aliphatic and cyclic esters. Mechanistic investigation indicated a metal ligand cooperated reaction pathway.
- Junge, Kathrin,Wendt, Bianca,Cingolani, Andrea,Spannenberg, Anke,Wei, Zhihong,Jiao, Haijun,Beller, Matthias
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supporting information
p. 1046 - 1052
(2018/01/01)
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- Magnetic Fe3O4@silica sulfuric acid nanoparticles promoted regioselective protection/deprotection of alcohols with dihydropyran under solvent-free conditions
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Protection (and deprotection) of hydroxyl groups via tetrahydropyranylation was carried out effectively using a catalytic amount of Fe3O4 supported silica sulphuric acid nanoparticles (Fe3O4@SiO2@SO3H) under solvent-free conditions. The synthesized nanocatalyst was characterized by XRD, TEM, FT-IR etc. A wide range of tetrahydropyranylated alcohol derivatives were synthesized using this heterogeneous magnetic nanocatalyst within 10-20 min with high yields. In addition, tetrahydropyranyl ethers could also be deprotected to the parent alcoholic compounds in the presence of MeOH using the same catalyst. After completion of the reactions, the catalyst was easily separated from the reaction medium using an external magnet, which ameliorated the overall synthetic process. The catalyst was recovered and reused for five successive reactions without any appreciable loss in its activity. Mild reactions conditions, operational simplicity, solvent free conditions, high selectivity, easy recyclability of the magnetic nanocatalyst, and high yields can be considered as the advantageous features of our procedure.
- Rajkumari, Kalyani,Kalita, Juri,Das, Diparjun,Rokhum, Lalthazuala
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p. 56559 - 56565
(2017/12/27)
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- A method for synthesizing L - menthol (by machine translation)
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The invention relates to a method for synthesizing L - menthol, comprises the following sequentially the steps of: (1) addition reaction; (2) the isomerization rearrangement reaction; (3) asymmetric hydrogenation reaction; (4) hydrolysis reaction; (5) the resulting compound IV L - menthol through reduced pressure distillation to remove the solvent to obtain the L - menthol crude, through recrystallization, L - menthol to obtain the finished product. This invention has overcome the existing L - menthol preparation method is complex, the need for chiral separation, the reaction yield is low, the great shortcoming of the damage to the environment, has a simple preparation method, without the need for chiral separation step, with high reaction yield, friendly advantage of the environment. (by machine translation)
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- Metal Nanoparticles Supported on Perfluorinated Superacid Polymers: A Family of Bifunctional Catalysts for the Selective, One-Pot Conversion of Vegetable Substrates in Water
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We describe the rational design of a new versatile family of bifunctional catalytic materials based on the combination of supported metal nanoparticles (Pd, Rh, Ru) and the superacid, perfluorinated Aquivion PFSA polymer. The heterogeneous catalysts were tested in the multi-step valorisation of representative plant derivatives to high-added-value chemicals. Particularly, the conversion of (+)-citronellal to (-)-menthol and levulinic acid to γ-valerolactone was achieved in one pot and in one stage in the water phase and shows full selectivity at a high conversion level under mild reaction conditions. The results are discussed in terms of the catalyst micro-structure.
- Moreno-Marrodan, Carmen,Liguori, Francesca,Barbaro, Pierluigi,Caporali, Stefano,Merlo, Luca,Oldani, Claudio
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p. 4256 - 4267
(2017/10/12)
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- Enantioselective enzymatic resolution of racemic alcohols by lipases in green organic solvents
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The effects of two eco-friendly solvents, 2-methyltetrahydrofuran (MeTHF) and cyclopentyl methyl ether (CPME), on the enzyme activity and enantioselectivity of Novozym 435, Candida rugosa lipase (CRL), Porcine pancreas lipase (PPL), Lipase AK, Lipase PS, and Lipozyme, a series of commercial lipases, in the enantioselective transesterfications of racemic menthol, racemic sulcatol and racemic α-cyclogeraniol were studied. Vinyl acetate was chosen as the acyl donor and the reactions were carried out at water activity 0.06. The activity of lipases in CPME was similar to that observed in other largely employed organic solvents [toluene and tert-butyl methyl ether (MTBE)], and was slightly lower in MeTHF. However, for most of the lipases tested, the enantioselectivity was higher in the eco-friendly solvents. Lipase AK exhibited a high enantioselectivity (E?=?232) for the resolution of racemic menthol but the reaction rate was low. Lipase formulation (the enzyme was frozen and lyophilized in potassium phosphate buffer without and with 5% (w/v) of sucrose, D-mannitol, or methoxy poly(ethylene glycol)) was tested with this lipase in order to improve its activity, which increased up to 4.5 times, compared to the untreated enzyme. CALB was found to be a useful biocatalyst for the resolution of racemic sulcatol, where high activity and enantioselectivity were obtained (E?≥?1000). For the resolution of the racemic primary alcohol α-cyclogeraniol, most of the lipases tested were active but not enantioselective, except lipase PS which displayed a moderate enantioselectivity (E?=?19). The effect of the presence of a low percentage of two ionic liquids (ILs) 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][TFSI]) (5% (v/v)) and 1-Butyl-3-methylimidazoliumtetrafluoroborate ([BMIM][BF4]) (1% (v/v)) in the medium was also investigated. Only in the case of CRL the ILs slightly increased the enantioselectivity from E?=?91 to E?=?103 and E?=?120 for [BMIM][TFSI] and [BMIM][BF4], respectively. However, in all cases ILs caused a decrease of enzyme activity.
- Belafriekh, Abderahmane,Secundo, Francesco,Serra, Stefano,Djeghaba, Zeineddine
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p. 473 - 478
(2017/03/23)
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- Expanding the scope of methyl xanthate esters - From Barton-McCombie reaction auxiliary to versatile protective group
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The methyl xanthate ester is presented as a versatile protective group for alcohols. Hydroxyl groups can easily be transformed into methyl xanthate esters by several methods and are commonly used as an auxiliary in the Barton-McCombie reaction. We show that these methyl xanthate esters can readily and chemoselectively be cleaved under mild conditions by the action of diethylenetriamine using microwave heating. This method is orthogonal to many common hydroxyl protective groups that can be introduced and cleaved in the presence of methyl xanthate ester.
- Thorsheim, Karin,Manner, Sophie,Ellervik, Ulf
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supporting information
p. 6329 - 6333
(2017/09/29)
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- Flow Pickering Emulsion Interfaces Enhance Catalysis Efficiency and Selectivity for Cyclization of Citronellal
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Cyclization of citronellal is a necessary intermediate step to produce the important flavor chemical (?)-menthol. Here, a continuous-flow Pickering emulsion (FPE) strategy for selective cyclization of citronellal to (?)-isopulegol by using water droplets hosting a heteropolyacid (HPA) catalyst to fill a column reactor is demonstrated. Owing to the large liquid–liquid interface and the excellent confinement ability of droplets toward HPA, the FPE system exhibited a much higher catalysis efficiency than its batch counterpart (2–5-fold) and an excellent durability (two months). Moreover, a remarkably enhanced selectivity was observed from 34.8 % for batch reactions to 64 % for the FPE reactions. It was found that the water droplet size and the flow rate significantly impact the catalysis selectivity and efficiency. This study not only represents an unprecedented and sustainable process for the selective cyclization of citronellal but also demonstrates a new flow-interface catalysis effect that can be useful for designing innovative catalysis systems in the future.
- Chen, Huan,Zou, Houbing,Hao, Yajuan,Yang, Hengquan
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p. 1989 - 1995
(2017/05/16)
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- A synthetic process of L-menthol
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The invention relates to the field of spice synthesis and particularly relates to a synthetic process of L-menthol. The process includes steps of d,l-menthol synthesizing, d,l-menthol rectification, d,l-menthol esterification, d,l-menthyl benzoate rectification, d,l-menthyl benzoate resolution, D-menthol synthesizing, menthol isomerization and L-menthol synthesizing. The process adopts thymol that is a simple, easily available and cheap chemical product as a raw material. Esterification conditions are optimized and the esterification and rectification are performed at the same time so as to allow the esterification to be converted into a way beneficial to d,l-menthyl benzoate production, thus increasing the esterification yield. Crystallization and resolution are optimized by utilization of the d,l-menthyl benzoate. Preparation of the L-menthol by the process is characterized by being high in yield, low in cost, simple and convenient in operation, suitable for continuous and large-scale production, and the like. According to the process, operation of the process is cyclic with a whole system being sealed, and the process is free of waste water, energy-saving and environmental friendly.
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- BENZO[H]QUINOLINE LIGANDS AND COMPLEXES THEREOF
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The present invention provides substituted tridentate benzo[h]quinoline ligands and complexes thereof. The invention also provides the preparation of the ligands and the respective complexes, as well as to processes for using the complexes in catalytic reactions.
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Page/Page column 73-75
(2016/12/22)
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- A removing the hydroxy group of a benzyl protecting group method (by machine translation)
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The invention discloses a process for the removal of the hydroxyl group of a method of a benzyl protecting group, the method is as follows: to the hydroxy compound by the hydroxy group with protection of the benzyl protecting group of the benzyl compound as reaction substrate, in order to 2, the 3 [...] two chloro -5,6 the [...] two cyanato -1, the 4 [...] benzoquinone (DDQ) and phthalocyanine ferrous (Fe II Pc) as catalyst, in order to 4,4 '-bipyridine (4, the 4 [...] -bpy) as an auxiliary agent, with oxygen as the oxidizing agent, in an organic solvent in the reaction substrate, the oxygen pressure 0.3-0.6 MPa, temperature 60-120 °C reaction is carried out under the condition of, removing the hydroxy group of a benzyl protecting group obtain hydroxyl compound. With the traditional use of chemical metering of oxidation with DDQ for the protection, the consumption of DDQ in this invention is greatly reduced, reducing the cost of reaction; with DDQ as catalyst, metal oxide or metal salt is compared with oxidation of the oxidizing agent for the protection, the used in the present invention oxygen as the oxidizing agent, reduces the environmental costs. (by machine translation)
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Paragraph 0032
(2016/11/07)
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- Sulfination of Alcohols with p-Toluenesulfonylmethyl Isocyanide under Metal-Free Conditions: A Mitsunobu Approach
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A Mitsunobu approach for the synthesis of sulfinate esters by direct nucleophilic substitution of alcohols is described. The salient features of this strategy include neutral and metal-free conditions for the rapid synthesis of sulfinates in high yields. The present protocol using p-toluenesulfonylmethyl isocyanide (TosMIC) and the triphenylphosphine (TPP)/diisopropyl azodicarboxylate (DIAD) reagent system represents the general synthetic route to this important class of compounds. (Figure presented.).
- Kadari, Lingaswamy,Radha Krishna, Palakodety,Lakshmi Prapurna
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supporting information
p. 3863 - 3868
(2016/12/16)
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- Hydrogenation of Esters to Alcohols Catalyzed by Defined Manganese Pincer Complexes
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The first manganese-catalyzed hydrogenation of esters to alcohols has been developed. The combination of Mn(CO)5Br with [HN(CH2CH2P(Et)2)2] leads to a mixture of cationic and neutral Mn PNP pincer complexes, which enable the reduction of various ester substrates, including aromatic and aliphatic esters as well as diesters and lactones. Notably, related pincer complexes with isopropyl or cyclohexyl substituents showed very low activity.
- Elangovan, Saravanakumar,Garbe, Marcel,Jiao, Haijun,Spannenberg, Anke,Junge, Kathrin,Beller, Matthias
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supporting information
p. 15364 - 15368
(2016/12/03)
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- ONE-POT PROCESS USING HETEROGENEOUS CATALYST
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The present invention relates to a process for the one-pot hydrogenation and dehydration or isomerization of an organic compound, and to a catalyst composition for this process comprising transition metal particles having particle size below 50 nm supported on a material comprising at least one fluorinated polymer (P), wherein polymer (P) bears -SO2X functional groups, X being selected from X' and OM, X' being selected from the groups consisting of F, CI, Br and I; and M being selected from the group consisting of H, and alkaline metal and NH4.
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-
Paragraph 0074; 0075; 0113
(2016/06/20)
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- Vanadium-Catalyzed Oxidative Debenzylation of O-Benzyl Ethers at ppm Level
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An advantageous methodology for the oxidative debenzylation of ethers has been developed. Very low amounts of a catalyst system based on vanadyl acetylacetonate and a triazole type pincer ligand allow the selective oxidative cleavage of a number of O-benzyl ethers in the presence of oxygen as the sole oxidant. The methodology tolerates a number of functional groups such as halo-, alkoxy-, or trifluoromethylarenes, alkyne, alkene, ether, and acetal units. Large-scale deprotections can be also carried out by the optimized procedure, which is amenable to enantioenriched reactants as well. (Figure presented.).
- Urgoitia, Garazi,SanMartin, Raul,Herrero, María Teresa,Domínguez, Esther
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p. 3307 - 3312
(2016/10/21)
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- Alcohol, Aldehyde, and Ketone Liberation and Intracellular Cargo Release through Peroxide-Mediated α-Boryl Ether Fragmentation
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α-Boryl ethers, carbonates, and acetals, readily prepared from the corresponding alcohols that are accessed through ketone diboration, react rapidly with hydrogen peroxide to release alcohols, aldehydes, and ketones through the collapse of hemiacetal intermediates. Experiments with α-boryl acetals containing a latent fluorophore clearly demonstrate that cargo can be released inside cells in the presence of exogenous or endogenous hydrogen peroxide. These experiments show that this protocol can be used for drug activation in an oxidative environment without generating toxic byproducts.
- Hanna, Ramsey D.,Naro, Yuta,Deiters, Alexander,Floreancig, Paul E.
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supporting information
p. 13353 - 13360
(2016/10/22)
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- Highly Productive and Enantioselective Enzyme Catalysis under Continuous Supported Liquid–Liquid Conditions Using a Hybrid Monolithic Bioreactor
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Enzyme-containing ionic liquids (ILs) were immobilized in cellulose-2.5-acetate microbeads particles embedded in a porous monolithic polyurethane matrix. This bioreactor was used under continuous liquid-liquid conditions by dissolving the substrates in a nonpolar organic phase immiscible with the ILs, thereby creating a biphasic system. Lipases (candida antarctica lipase B, CALB, candida rugosa lipase, CRL) were used to catalyze the enantioselective transesterification of racemic (R,S)-1-phenylethanol with vinyl butyrate and vinyl acetate, the esterification of (+/-)-2-isopropyl-5-methylcyclohexanol with propionic anhydride and the amidation of (R,S)-1-phenylethylamine with ethyl methoxyacetate. With this unique setup, very high productivities, that is, turnover numbers (TONs) up to 5.1×106 and space-time yields (STYs) up to 28 g product L?1 h?1, exceeding the corresponding values for batch-type reactions by a factor of 3100 and 40, respectively, were achieved while maintaining or even enhancing enantioselectivity compared to batch reactions via kinetic resolution. To our best knowledge, this is the first continuously operated bioreactor using supported liquid-liquid conditions that shows these features in the synthesis of chiral esters and amides.
- Sandig, Bernhard,Buchmeiser, Michael R.
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p. 2917 - 2921
(2016/11/02)
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