- An Enzymatic Route to α-Tocopherol Synthons: Aromatic Hydroxylation of Pseudocumene and Mesitylene with P450 BM3
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Aromatic hydroxylation of pseudocumene (1 a) and mesitylene (1 b) with P450 BM3 yields key phenolic building blocks for α-tocopherol synthesis. The P450 BM3 wild-type (WT) catalyzed selective aromatic hydroxylation of 1 b (94 %), whereas 1 a was hydroxylated to a large extent on benzylic positions (46–64 %). Site-saturation mutagenesis generated a new P450 BM3 mutant, herein named “variant M3” (R47S, Y51W, A330F, I401M), with significantly increased coupling efficiency (3- to 8-fold) and activity (75- to 230-fold) for the conversion of 1 a and 1 b. Additional π–π interactions introduced by mutation A330F improved not only productivity and coupling efficiency, but also selectivity toward aromatic hydroxylation of 1 a (61 to 75 %). Under continuous nicotinamide adenine dinucleotide phosphate recycling, the novel P450 BM3 variant M3 was able to produce the key tocopherol precursor trimethylhydroquinone (3 a; 35 % selectivity; 0.18 mg mL?1) directly from 1 a. In the case of 1 b, overoxidation leads to dearomatization and the formation of a valuable p-quinol synthon that can directly serve as an educt for the synthesis of 3 a. Detailed product pattern analysis, substrate docking, and mechanistic considerations support the hypothesis that 1 a binds in an inverted orientation in the active site of P450 BM3 WT, relative to P450 BM3 variant M3, to allow this change in chemoselectivity. This study provides an enzymatic route to key phenolic synthons for α-tocopherols and the first catalytic and mechanistic insights into direct aromatic hydroxylation and dearomatization of trimethylbenzenes with O2.
- Dennig, Alexander,Weingartner, Alexandra Maria,Kardashliev, Tsvetan,Müller, Christina Andrea,Tassano, Erika,Schürmann, Martin,Ruff, Anna Jo?lle,Schwaneberg, Ulrich
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- Efficient and chemoselective hydrogenation of aldehydes catalyzed by well-defined PN3-pincer manganese(ii) catalyst precursors: An application in furfural conversion
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Well-defined and air-stable PN3-pincer manganese(ii) complexes were synthesized and used for the hydrogenation of aldehydes into alcohols under mild conditions using MeOH as a solvent. This protocol is applicable for a wide range of aldehydes containing various functional groups. Importantly, α,β-unsaturated aldehydes, including ynals, are hydrogenated with the CC double bond/CC triple bond intact. Our methodology was demonstrated for the conversion of biomass derived feedstocks such as furfural and 5-formylfurfural to furfuryl alcohol and 5-(hydroxymethyl)furfuryl alcohol respectively.
- Gholap, Sandeep Suryabhan,Dakhil, Abdullah Al,Chakraborty, Priyanka,Li, Huaifeng,Dutta, Indranil,Das, Pradip K.,Huang, Kuo-Wei
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supporting information
p. 11815 - 11818
(2021/11/30)
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- Visible Light Induced Reduction and Pinacol Coupling of Aldehydes and Ketones Catalyzed by Core/Shell Quantum Dots
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We present an efficient and versatile visible light-driven methodology to transform aryl aldehydes and ketones chemoselectively either to alcohols or to pinacol products with CdSe/CdS core/shell quantum dots as photocatalysts. Thiophenols were used as proton and hydrogen atom donors and as hole traps for the excited quantum dots (QDs) in these reactions. The two products can be switched from one to the other simply by changing the amount of thiophenol in the reaction system. The core/shell QD catalysts are highly efficient with a turn over number (TON) larger than 4 × 104 and 4 × 105 for the reduction to alcohol and pinacol formation, respectively, and are very stable so that they can be recycled for at least 10 times in the reactions without significant loss of catalytic activity. The additional advantages of this method include good functional group tolerance, mild reaction conditions, the allowance of selectively reducing aldehydes in the presence of ketones, and easiness for large scale reactions. Reaction mechanisms were studied by quenching experiments and a radical capture experiment, and the reasons for the switchover of the reaction pathways upon the change of reaction conditions are provided.
- Xi, Zi-Wei,Yang, Lei,Wang, Dan-Yan,Feng, Chuan-Wei,Qin, Yufeng,Shen, Yong-Miao,Pu, Chaodan,Peng, Xiaogang
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p. 2474 - 2488
(2021/02/05)
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- A novel application of [Cr(en)2]2+ in the synthesis of 1,2-diols from aromatic aldehydes
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A reductive pinacol type arylaldehyde homocoupling process mediated by the [Cr(en)2]2+ complex is described. This procedure affords the mavo-stereoisomer as the major product, an unexpected result considering that most organometallic methodologies preferentially yield the dl-isomer. Additionally, the method represents a novel application of the [Cr(en) 2]2+.
- Avila-Sorrosa, Alcives,Vega-Ramirez, Leticia,Rodriguez-Dominguez, Rafael,Salgado-Zamora, Hector,Peralta-Cruz, Javier,Reyes-Arellano, Alicia
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supporting information; experimental part
p. 500 - 501
(2010/08/22)
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- Selective lithiation of 4- and 5-halophthalans
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The reaction of 4- and 5-halophthalans 5 with lithium and a catalytic amount of DTBB at -78 °C leads to the formation of the corresponding functionalized organolithium intermediates 6 and 11, which by reaction with carbonyl compounds give, after hydrolysis, the expected substituted phthalans 8 and 13, respectively. When after reaction with the carbonyl compound the system is allowed to react at 0 °C, a second lithiation occur: A reductive opening of the heterocycle takes place with some regioselectivity leading to new organolithium intermediates 9 and 14/15 that by reaction with electrophiles lead, after hydrolysis, to polyfunctionalized molecules 10 and 16/17, respectively.
- Garcia, Daniel,Foubelo, Francisco,Yus, Miguel
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experimental part
p. 991 - 1005
(2010/10/03)
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- PYRROLOY2,3-c¨PYRIDINE COMPOUND, PROCESS FOR PRODUCING THE SAME, AND USE
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Provision of a compound having a superior proton pump action, which shows an antiulcer activity and the like after conversion to an in vivo proton pump inhibitor, a production method thereof and use thereof. A pyrrolo[2,3-c]pyridine compound represented by the formula: wherein each symbol is as defined in the specification.
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Page/Page column 45
(2010/11/27)
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- Fast and chemoselective transfer hydrogenation of aldehydes catalyzed by a terdentate CNN ruthenium complex [RuCl(CNN)(dppb)]
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Aromatic, aliphatic and α,β-unsaturated aldehydes are quickly, quantitatively and chemoselectively reduced to primary alcohols with 2-propanol using 0.05-0.01 mol% of the terdentate CNN ruthenium complex RuCl(CNN)(dppb) (1) [HCNN = 6-(4′-methylphenyl)-2-pyridylmethylamine; dppb = Ph 2P(CH2)4PPh2] in the presence of potassium carbonate (K2CO3; 1-10 mol%) as a weak base, affording TOF values up to 5.0 × 105 h-1.
- Baratta, Walter,Siega, Katia,Rigo, Pierluigi
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p. 1633 - 1636
(2008/02/11)
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- Paracyclophanes. Part 58 [1]. On the use of the stilbene-phenanthrene photocyclization in [2.2]paracyclophane chemistry
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The application of the stilbene→phenanthrene photocyclization to [2.2]paracyclophane chemistry has been investigated. For the model system 4-styryl[2.2]paracyclophane (2) to [2.2]phenanthrenoparacyclophane (3) the reaction allows the introduction of alkyl substituants in the 6-, 7-, 8- and 9-position of the phenanthrene moiety. However, when the substituent in the 9-position (bay area of phenanthrene nucleus) becomes too large, viz. tert-butyl, no ring closure is observed anymore. The side products of the process (ring cleavage products of the cyclophane core such as 9 and 10) have been characterized for the first time. Extension of the condensed deck is possible leading to PAH-phanes as demonstrated by the preparation of the chrysenophanes 45 and 60; the cyclization to novel helicenophanes such as 50 also takes place without difficulties. In the case of 1,2-di(4-[2.2] paracyclophanyl)ethene (63) the triply-layered hydrocarbon 65 is produced on irradiation in small amounts.
- Hopf,Hucker,Ernst
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p. 947 - 969
(2008/09/17)
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- Process for producing alicyclic aldehydes
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In the production of an alicyclic aldehyde, a starting aromatic aldehyde is converted into an aromatic acetal for protecting the formyl group. The aromatic ring of the aromatic acetal is then hydrogenated to convert the aromatic acetal into an alicyclic acetal, which is then hydrolyzed to cleave the acetal protecting group to obtain the aimed alicyclic aldehyde.
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Page/Page column 5-6
(2008/06/13)
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- Process for producing cyclopropanecarboxylates
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There is disclosed a process process for producing a cyclopropanecarboxylate of formula (1): 1which process comprises reacting cyclopropanecarboxylic acid of formula (2): 2with a monohydroxy compound of formula (3): R6OH??(3),in the presence of a catalyst compound comprising an element of to Group 4 of the Periodic Table of Elements.
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- One-pot reduction of carboxylic acids via O-acylisoureas
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A simple one-pot reduction of aliphatic carboxylic acids to primary alcohols, by treatment with dicyclohexylcarbodiimide followed by lithium borohydride, is reported. The same methodology applied to aromatic carboxylic acids is shown to give a mixture of the alcohols with N- cyclohexylcarboxamides.
- Herbert, John M.,Hewson, Alan T.,Peace, James E.
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p. 823 - 832
(2007/10/03)
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- A Convenient Procedure for the Reduction of Esters, Carboxylic Acids, Ketones and Aldehydes using Tetrabutylammonium Fluoride (or Triton B) and Polymethylhydrosiloxane
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A range of carboxylic esters and acids have been converted efficiently to the corresponding alcohols with polymethylhydrosiloxane in the presence of catalytic tetrabutylammonium fluoride. The reduction of ketones and aldehydes with PMHS and other alkoxysilanes in the presence of TBAF or benzyltrimethylammonium hydroxide is also described.
- Drew, Mark D.,Lawrence, Nicholas J.,Fontaine, David,Sehkri, Lakhdar,Bowles, Stephen A.,Watson, William
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p. 989 - 991
(2007/10/03)
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- Aromatic Spiranes XX [1]: Syntheses of Dimethylsubstituted 2-Carboxymethyl-indan-1-ones and Benzylchlorides as Synthones for Syntheses of di- to tetramethylsubstituted Spirobiindandiones
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The isomeric dimethyl methylbenzoates 5, obtained from the bromides via Grignard reactions with dimethylcarbonate, were reduced with LiAlH4 to the hydroxymethyl derivatives 6. The latter were then transformed both to the benzylchlorides 7 (with SOCl2) and to the aldehydes 8 (with pyridinium chlorochromate). Knoevenagel-Doebner reaction of 8 afforded the acrylic acids 9 which (after hydrogenation to 11) were cyclized to the desired indanones 12 with polyphosphoric acid. On the other hand, 12c and 12e were prepared from dimethyl 3-chloropropiophenone (14) by warming with sulfuric acid. After NaH-catalyzed reaction with dimethylcarbonate, the indanones 12 gave the ketoesters 15 which then could be hydrogenated to the indanes 16. All reactions proceeded with satisfactory to excellent yields (60-90%).
- Neudeck
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p. 185 - 200
(2007/10/03)
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