- Ligand-Controlled Palladium-Catalyzed Alkoxycarbonylation of Allenes: Regioselective Synthesis of α,β- and β,γ-Unsaturated Esters
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The palladium-catalyzed regioselective alkoxycarbonylation of allenes with aliphatic alcohols allows to produce synthetically useful α,β- and β,γ-unsaturated esters in good yields. Efficient selectivity control is achieved in the presence of appropriate ligands. Using Xantphos as the ligand, β,γ-unsaturated esters are produced selectively in good yields. In contrast, the corresponding α,β-unsaturated esters are obtained with high regioselectivity in the presence of PPh2Py as the ligand. Preliminary mechanistic studies revealed that these two catalytic processes proceed by different reaction pathways. In addition, this novel protocol was successfully applied to convert an industrially available bulk chemical, 1,2-butadiene, into dimethyl adipate, which is a valuable feedstock for polymer and plasticizer syntheses, with high yield and TON (turnover number).
- Liu, Jie,Liu, Qiang,Franke, Robert,Jackstell, Ralf,Beller, Matthias
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supporting information
p. 8556 - 8563
(2015/07/15)
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- Organocatalytic asymmetric formal [3 + 2] cycloaddition with in situ-generated N-carbamoyl nitrones
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(Chemical Equation Presented) A novel organocatalytic formal [3 + 2] cycloaddition reaction with in situ generation of N-carbamoyl nitrones is presented. For the first time, N-Boc- and N-Cbz-protected isoxazolidines have been directly obtained as single diastereoisomers in generally high yields and enantiomeric excesses using mild reaction conditions and inexpensive, readily available Cinchona alkaloid quaternary ammonium salts as catalysts. Synthetic manipulations of the products provided highly valuable building blocks such as free isoxazolidines, a N-Boc-1,3-aminoalcohol, and a free δ-lactam. This report represents a pioneering work in the use of N-carbamoyl nitrones as electron-poor 1,3-dipoles and glutaconates as new dipolarophiles in asymmetric catalysis.
- Gioia, Claudio,Fini, Francesco,Mazzanti, Andrea,Bernardi, Luca,Ricci, Alfredo
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supporting information; experimental part
p. 9614 - 9615
(2011/02/23)
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- Molybdenum Hexacarbonyl Catalyzed Cyclopropanation of α,β-Unsaturated Esters and Nitriles with Diazocarbonyl Compounds
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Molybdenum hexacarbonyl, when employed in catalytic amounts, effectively promotes cyclopropanation of acrylonitrile, methacrylonitrile, and ethyl acrylate by ethyl diazoacetate and α-diazoacetophenone; the intermediacy of molybdenum carbene species in the formation of cyclopropane derivatives is suggested.
- Doyle, Michael P.,Davidson, James G.
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p. 1538 - 1539
(2007/10/02)
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