- Metal-Free C-O Bond Functionalization: Catalytic Intramolecular and Intermolecular Benzylation of Arenes
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A catalytic, metal-free intramolecular rearrangement of benzyl phenyl ethers using nitrosonium salt as a catalyst is described. The optimized reaction conditions enabled a catalytic and metal-free Friedel-Crafts alkylation reaction with benzylic alcohols, producing water as the stoichiometric byproduct. A comprehensive scope (>50 examples) for both approaches and application in drug synthesis were demonstrated. Mechanistic studies suggest a Lewis acid-based mechanism for the metal-free Friedel-Crafts reaction.
- Bering, Luis,Jeyakumar, Kirujan,Antonchick, Andrey P.
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supporting information
p. 3911 - 3914
(2018/07/22)
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- Selective debenzylation of aromatic benzyl ethers by silica-supported sodium hydrogen sulfate
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A new debenzylation of aromatic benzyl ethers by silica-supported sodium hydrogen sulfate is described. The process proceeds selectively and efficiently in good to excellent yields without affecting sensitive functional groups such as nitro, COOMe, aldehyde, ketone, and tosyl.
- Zhou, Linna,Wang, Wenjing,Zuo, Li,Yao, Shanyan,Wang, Wei,Duan, Wenhu
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p. 4876 - 4878
(2008/09/21)
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- An effective bismuth-catalyzed benzylation of arenes and heteroarenes
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A highly efficient Bi(OTf)3-catalyzed benzylation of arenes and heteroarenes has been developed. The mild reaction conditions, high yields, operational simplicity and practicability, broad scope, and remarkably low catalyst loading render this environment friendly process an attractive approach to diarylmethane derivatives. The extension to an intramolecular variant of this procedure provides a valuable route to substituted fluorenes.
- Rueping, Magnus,Nachtsheim, Boris J.,Ieawsuwan, Winai
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p. 1033 - 1037
(2007/10/03)
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- Asymmetric transfer of nitrenes catalyzed by chiral dirhodium(II) using aromatic sulfamate esters
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Enantioselective intra- and intermolecular insertions of aromatic sulfamate esters into activated C-H bonds have been achieved via in situ generated phenyliodinanes in the presence of PhI(OAc)2, MgO, and chiral Rh(II) catalysts. The optimal results were obtained with [Rh 2{(S)-nttl}4] and [Rh2{(R)-ntv}4] as catalysts with up to 52% ee. In contrast, phenylsulfamates with allylic ortho-substituents reacted via intramolecular aziridination rather than insertion. The intermolecular amidation of indane proceeded with up to 97% yield when the reaction was carried out with the sulfamate in excess.
- Fruit, Corinne,Mueller, Paul
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p. 1019 - 1026
(2007/10/03)
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- BENZYLPHENOL DERIVATIVES AS ANTIOXIDANTS FOR AUTOXIDATION OF TETRALIN.
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A series of 4-benzylphenols, 2-methyl-4-benzylphenols, 4-methyl-2-benzylphenols and 4-methoxy-2-benzylphenols have been prepared and evaluated as antioxidants for tetralin at 60 degree C by means of an oxygen-absorption method. Very good activities have been observed with a series of 4-methoxy-2-benzylphenols. The electrochemical oxidation potentials of these compounds were determined using linear-sweep voltammetry. The antioxidative activities were found to correlate with both the **1**3C NMR chemical shifts ( delta ) of the ipsocarbon of the OH substituents and their peak potentials (E//p).
- Yamada,Nishiyama,Suzuura,Yamamura
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p. 115 - 119
(2007/10/02)
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- MECHANISMUS DER PHOTO-UMLAGERUNG VON BENZYLARYLETHERN
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Aus Absorptions- and Emissionsspektren konnten die ES- and ET-Werte einiger Benzylarylether bestimmt werden.Die Photo-Claisen-Umlagerung dieser Ether erfolgt aus dem S1-Zustand, wie durch Sensibilisierungs- and Loeschexperimente mit aromatischen Kohlenwasserstoffen bzw.Diacetyl bewiesen wurde.Bei der Photolyse werden primaer Benzyl- und Phenoxyradikale gebildet, deren Entstehen durch Spin-Trapping-Experimente bewiesen wurde.Die Spaltung der Ether geschieht mit hohen Quantenausbeuten, die wenig von Substituenten sowohl im Phenoxy- als auch im Benzylteil der Ether beeinflusst werden.In protischen Loesungsmitteln steigen die Werte geringfuegig an.Die Quantenausbeuten fuer die Reaktionsprodukte wurden ebenfalls bestimmt; deren Summe ergibt die Groesse fuer den Etherabbau.Die Produktverteilung bei der Photolyse einiger p-substituierter Ether legt nahe, dass die Benzylradikale auch in p-Stellung der Phenoxyradikale angreifen.Es wird ein allgemeiner Mechanismus diskutiert and kinetisch modelliert.Dadurch werden die Geschwindigkeitskonstanten einiger Teilschritte zugaenglich und wahrscheinlich gemacht, dass die Radikale auch zum Ether rekombinieren.
- Timpe, Hans-Joachim,Dietrich, Reinhard,Boeckelmann, Juergen,Friedel, Ingrid,Boegel, Horst,Haucke, Guenther
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p. 219 - 239
(2007/10/02)
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