- 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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supporting information
p. 4096 - 4108
(2021/08/19)
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- Chemoenzymatic synthesis of enantiomerically pure syn-configured 1-aryl-3-methylisochroman derivatives
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A two-step synthesis of various enantiomerically pure 1-aryl-3- methylisochroman derivatives was accomplished through asymmetric biocatalytic ketone reduction followed by an oxa-Pictet-Spengler reaction. The compounds were obtained in good to excellent yield (47-92 %) in favor of the syn diastereomers [dr (syn/anti) up to 99:1]. Enantiopure arylpropanols serving as pronucleophiles for the C-C bond-formation step were obtained by biocatalytic reduction by employing enantiocomplementary alcohol dehydrogenases, which gave access to the (S) and (R) enantiomer with up to >99 % conversion and up to >99 % ee. A two-step sequence involving a biocatalytic hydrogen-transfer reduction and a syn-diastereoselective oxa-Pictet-Spengler reaction was established to provide a series of 1-aryl-3-methylchroman derivatives with perfect enantioselectivity; PTSA = para-toluenesulfonic acid. Copyright
- Simon, Robert C.,Busto, Eduardo,Richter, Nina,Belaj, Ferdinand,Kroutil, Wolfgang
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p. 111 - 121
(2014/01/06)
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- A simple and efficient synthesis of GYKI 52466 and GYKI 52895
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The synthesis of 1-(4-aminophenyl)-4-methyl-7,8-methylene-dioxy-5H-2,3-benzodiazepine (GYKI 52466, 1), the prototype of a series of noncompetitive AMPA receptor antagonists, and its 3,4-dihydroderivative (GYKI 52895, 2) is described. The title compounds have been prepared starting from safrole through a quite effective procedure.
- Zappala, Maria,Grasso, Silvana,Micale, Nicola,Polimeni, Santina,De Micheli, Carlo
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p. 527 - 533
(2007/10/03)
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- Sodium Perborate: A Mild and Convenient Reagent for Efficiently Oxidizing Organoboranes
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Sodium perborate, a readily available and inexpensive reagent, efficiently oxidizes organoboranes.The reagent permits the oxidation of a wide variety of functionally substituted organoboranes.In nearly every instance, the product yields exceed those obtained using standard oxidation procedures.
- Kabalka, George W.,Shoup, Timothy M.,Goudgaon, Naganna M.
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p. 5930 - 5933
(2007/10/02)
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- Isocoumarins : Part III - Synthesis of Methyl- and Methylenedioxydihydroisocoumarins and a New Synthesis of (+/-)-5-Methylmellein
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o-Lithio-N-methylbenzamide upon condensation with propylene oxide gives 3-methyldihydroisocoumarin.Similarly o-lithio-N-methyl-p-toluamide upon condensation with ethylene oxide and propylene oxide give 6-methyl- and 3,6-dimethyldihydroisocoumarin.A similar condensation of o-lithio-N-methyl-m-toluamide with ethylene oxide gives 5-methyldihydroisocoumarin but condensation with propylene oxide gives 3,5-dimethyl- and 3,7-dimethyldihydroisocoumarins.The method has been used to synthesize (+/-)-5-methylmellein.The synthesis of 5,6-methylenedioxydihydroisocoumarin from o-lithio-N-methylpiperonylamide is also described. 3-Methyl-6,7-methylenedioxydihydroisocoumarin has been synthesized by an acid-catalyzed cyclization reaction.
- Bhide, Bhaskar H.,Shah, Kashmira K.
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