- Markovnikov Wacker-Tsuji Oxidation of Allyl(hetero)arenes and Application in a One-Pot Photo-Metal-Biocatalytic Approach to Enantioenriched Amines and Alcohols
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The Wacker-Tsuji aerobic oxidation of various allyl(hetero)arenes under photocatalytic conditions to form the corresponding methyl ketones is presented. By using a palladium complex [PdCl2(MeCN)2] and the photosensitizer [Acr-Mes]ClO4 in aqueous medium and at room temperature, and by simple irradiation with blue led light, the desired carbonyl compounds were synthesized with high conversions (>80%) and excellent selectivities (>90%). The key process was the transient formation of Pd nanoparticles that can activate oxygen, thus recycling the Pd(II) species necessary in the Wacker oxidative reaction. While light irradiation was strictly mandatory, the addition of the photocatalyst improved the reaction selectivity, due to the formation of the starting allyl(hetero)arene from some of the obtained by-products, thus entering back in the Wacker-Tsuji catalytic cycle. Once optimized, the oxidation reaction was combined in a one-pot two-step sequential protocol with an enzymatic transformation. Depending on the biocatalyst employed, i. e. an amine transaminase or an alcohol dehydrogenase, the corresponding (R)- and (S)-1-arylpropan-2-amines or 1-arylpropan-2-ols, respectively, could be synthesized in most cases with high yields (>70%) and in enantiopure form. Finally, an application of this photo-metal-biocatalytic strategy has been demonstrated in order to get access in a straightforward manner to selegiline, an anti-Parkinson drug. (Figure presented.).
- Albarrán-Velo, Jesús,Gotor-Fernández, Vicente,Lavandera, Iván
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p. 4096 - 4108
(2021/08/19)
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- Chemo- and Regioselective Asymmetric Friedel-Crafts Reaction of Furans and Thiophenes with α,β-Unsaturated Aldehydes through Dual Activation
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A highly chemo- and regioselective Friedel-Crafts alkylation reaction of furans and thiophenes has been developed, which relies on the activation from the remote conjugated Mukaiyama silyl enol ether motif. Excellent enantioslectivity is generally obtained in reactions with α,β-unsaturated aldehydes under the well-established iminium ion catalysis of a chiral secondary amine.
- Zhang, Xiao-Ru,Zhou, Su-Lan,Yuan, Yi,Du, Wei,Chen, Ying-Chun
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supporting information
p. 1771 - 1774
(2017/09/30)
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- Gold catalysis: benzanellation versus alkylidenecyclopentenone synthesis
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A series of different furan-yn-ols were prepared by a three-step sequence. Their reaction with Gagosz's catalyst Ph3PAuNTf2 depends strongly on the substitution pattern of the substrate and the quality of the leaving group. Benzofurans, alkylidenecyclopentenones or Meyer-Schuster type products can be obtained. Improving the leaving group quality leads to the preferred formation of benzofurans.
- Hashmi, A. Stephen K.,W?lfle, Michael
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experimental part
p. 9021 - 9029
(2009/12/08)
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- Fe-HCl: An efficient reagent for deprotection of oximes as well as selective oxidative hydrolysis of nitroalkenes and nitroalkanes to ketones
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Fe-HCl mixture was found to selectively perform oxidative hydrolysis of the nitroalkenes 1a-j and nitroalkanes 2a-j to the ketones 3a-j. Also, the reagent was observed to deprotect the oximes 7a-j to carbonyl compounds 8a-j in excellent yields.
- Pradhan, Prasun K.,Dey, Sumit,Jaisankar, Parasuraman,Giri, Venkatachalam S.
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p. 913 - 922
(2007/10/03)
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- Novel Compounds
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The invention relates to heteroaromatic carboxamides of formula (I), wherein A, R1, R2 and X are as defined in the specification, processes and intermediates used in their preparation, pharmaceutical compositions containing them and their use in therapy.
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- Homochiral (R)- and (S)-1-heteroaryl- and 1-aryl-2-propanols via microbial redox
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Preparation of various heteroaryl propanols 2a-g and of the corresponding propanones 3a-g as starting materials for microbial redox is described. The kinetic resolution of the racemic propanols 2a-g is obtained via oxidation with Pseudomonas paucimobilis and Bacillus stearothermophilus [(R)-alcohols, ee 74-100%]. Similar results are achieved with 3-(2- hydroxypropyl)trifluoromethylbenzene 7 (44%, ee 100% of the (R)-alcohol 6). The reduction of the propanones 3a-d and 3g with baker's yeast and other fungi gives the (S)-alcohols (ee 100%). The pure (S)-alcohols are also obtained by reduction of 1-[3-(trifluoromethyl)phenyl]-2-propanone 7. 1- [(4,4-Dimethyl)-2-(Δ2)oxazolinyl]-2-propanone 3e and 1[2-(Δ2)- thiazolinyl)-2-propanone 3f are not reduced. The heterocyclic rings of (S)- 5-(2-hydroxypropyl)-3-methylisoxazole 2d and of (S)-2-(2-hydroxypropyl)-4- methylthiazole 2g are deblocked to the homochiral enamino ketone 8 (78%) and to the protected β-hydroxy aldehyde 9 (73%), respectively. The (R)-3-(2- hydroxypropyl)trifluoromethylbenzene 6 is transformed into the homochiral precursor of (S)-fenfluramine 10 (overall yield 65%).
- Fogagnolo, Marco,Giovannini, Pier Paolo,Guerrini, Alessandra,Medici, Alessandro,Pedrini, Paola,Colombi, Nicola
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p. 2317 - 2327
(2007/10/03)
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- Rearrangements of some furan and benzofuran 1,5,-dienols
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Isomers of 1-(2-furyl)-methyl-3-buten-ols and their benzofuran analogs were studied for their oxy-Cope and anionic oxy-Cope reactivity.
- Martin,Wurster,Boylan,Borzilleri,Engel,Walsh
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p. 8395 - 8398
(2007/10/02)
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- GENERAL RELATIONSHIPS IN THE OPENING OF THE OXIRANE RING DURING CLEAVAGE OF GLYCIDIC ACIDS
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By investigation of the decarboxylation of 2,3-epoxy derivatives of acids with various structures it was shown that contrary to the existing theory about the essential opening of the β (C-O) bond in the oxirane ring there are many structural types of 2,3-epoxypropionic acids, in which opening of the α (C-O) bond in the oxirane ring occurs during decarboxylation.It was also shown that these two possible reaction paths can also arise during the decarboxylation of one 2,3-epoxypropionic acid.On the basis of the obtained data a general relationship is developed for theopening of the oxirane ring during the decarboxylation of 2,3-epoxypropionic acids with any structure, and this makes it possible to predict the structure of the obtained carbonyl compound.
- Kuroyan, R. A.,Markosyan, A. I.,Engoyan, A. P.,Vartanyan, S. A.
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p. 1709 - 1714
(2007/10/02)
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- Syntheses of Arylacetone and Arylacetonitrile by Friedel-Crafts Reaction with α-Chloro-α-(methylthio)-substituted Acetone and Acetonitrile
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Novel preparative methods for arylacetone and arylacetonitrile are described.Friedel-Crafts reactions of aromatic compounds with α-chloro-α-(methylthio)acetone (4) and α-chloro-α-(methylthio)acetonitrile (7) in the presence of Lewis acid afforded α-(methylthio)arylacetone (5) and α-(methylthio)arylacetonitrile (8), respectively.Compounds (5) and (8) were converted into the corresponding arylacetone (6) and arylacetonitrile (9) by reduction with zinc dust in acetic acid.Keywords: Friedel-Crafts reaction with α-chloro-α-(methylthio)acetone; Friedel-Crafts reaction with α-chloro-α-(methylthio)acetonitrile; α-(methylthio)arylacetone; α-(methylthio)arylacetonitrile; arylacetone; arylacetonitrile; reductive desulfurization; zinc dust-acetic acid
- Tamura, Yasumitsu,Choi, Hong Dae,Mizutani, Masako,Ueda, Yuko,Ishibashi, Hiroyuki
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p. 3574 - 3579
(2007/10/02)
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