- [3,3]-Sigmatropic rearrangement step in the gold-catalyzed cyclization of allyl-(ortho-alkinylphenyl)methyl ethers
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The gold-catalyzed conversion of allyl-(ortho-alkynylphenyl)methyl ethers was investigated, and allylated isochromenes were obtained. An optimization of the catalysis conditions with respect to different phosphane and carbene ligands on gold, different counterions, and different solvents was conducted. Subsequently, the scope and limitations of this reaction were investigated with 21 substrates. The mechanistic studies show an allylic inversion, as supported by NMR data and an X-ray crystal structure analysis, as well as an intermolecular reaction, as determined by crossover experiments. There is no competition of protodeauration even in the presence of water. All these observations differ from other related conversions and clearly indicate product formation by a [3,3]sigmatropic rearrangement in the step forming the new C-C bond. The Golden Key: Allylic inversion and crossover experiments reveal a sigmatropic rearrangement as a key step in the gold-catalyzed intramolecular allyl transfer in ortho-alkinyl benzyl allyl ethers. Copyright
- Ackermann, Martin,Bucher, Janina,Rappold, Melissa,Graf, Katharina,Rominger, Frank,Hashmi, A. Stephen K.
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supporting information
p. 1786 - 1794
(2013/09/02)
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- Synthesis of (±)-3-methoxyestra-1,3,5(10)-trienes by the repetitive use of Negishi reagent
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The repetitive use of Cp2ZrBu2 (Negishi reagent) was applied in the synthesis of three 3-methoxyestra-1,3,5(10)-trienone isomers within four steps from the advanced intermediate 11. The overall synthesis is based on three zirconium-m
- Herrmann, Pavel,Kotora, Martin,Budesinsky, Milos,Saman, David,Cisarova, Ivana
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p. 1315 - 1318
(2007/10/03)
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- Palladium-catalyzed cross-coupling of 2,5-cyclohexadienyl-substituted aryl or vinylic iodides and carbon or heteroatom nucleophiles
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2,5-Cyclohexadienyl-substituted aryl or vinylic iodides have been reacted with carbon nucleophiles (diethyl malonate and 2-methyl-1,3- cyclohexanedione), nitrogen nucleophiles (morpholine, potassium phthalimide, N-benzyl tosylamide, di-tert-butyl iminodicarboxylate, lithium azide, and anilines), a sulfur nucleophile (sodium benzenesulfinate), and oxygen nucleophiles (lithium acetate and phenols) to afford products of cyclization and subsequent cross-coupling in good to excellent yields. In most cases, this process is highly diastereoselective. The reaction is believed to proceed via (1) oxidative addition of the aryl or vinylic iodide to Pd(0), (2) organopalladium addition to one of the carbon-carbon double bonds, (3) palladium migration along the carbon chain on the same face of the ring to form a π-allylpalladium intermediate, and (4) nucleophilic displacement of the palladium.
- Larock, Richard C.,Han, Xiaojun
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p. 1875 - 1887
(2007/10/03)
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- Accelerating effect induced by the structure of α-amino acid in the copper-catalyzed coupling reaction of aryl halides with α-amino acids. Synthesis of benzolactam-V8
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The coupling of optically pure α-amino acids with aryl halides produces enantiopure N-aryl-α-amino acids with retention of configuration under the catalysis of CuI. This reaction can complete at much lower temperature than typical Ullmann condensation even for electron-rich aryl halides, which indicates that an accelerating effect induced by the structure of the α- amino acid exists in this reaction. α-Amino acids with larger hydrophobic groups give higher coupling yields, while those with smaller hydrophobic groups only deliver lower yields and no coupling products were detected for those with hydrophilic groups. No racemization was observed in most cases of this coupling reaction. After some controlled experiments, a possible mechanism including the π-complex and the intramolecular substitution reaction is proposed. Based on this catalyzed reaction, a facile and stereoselective synthesis of benzolactam-V8, a new PKC activator, is achieved.
- Ma, Dawei
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p. 12459 - 12467
(2007/10/03)
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