- Bidentate auxiliary-directed alkenyl C-H allylation: Via exo-palladacycles: Synthesis of branched 1,4-dienes
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An alkenyl C-H allylation by an exo-palladacycle intermediate is demonstrated, employing unactivated (Z)-Alkenes and allyl carbonates. With the use of an 8-Aminoquinoline (AQ) derived amide as the directing group, the N,N-bidentate-chelation-Assisted C-H activation protocol proceeded under mild and oxidant-free conditions with excellent selectivity. The utility of this approach is demonstrated by the preparative scale, selective conversion of inseparable Z/E alkenes and ready removal of the amide auxiliary to provide the corresponding ester.
- Shen, Cong,Lu, Xiunan,Zhang, Jian,Ding, Liyuan,Sun, Yaling,Zhong, Guofu
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supporting information
p. 13582 - 13585
(2019/11/14)
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- Synthetic studies toward isoschizogamine: Construction of pentacyclic core structure
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Development of a concise construction of the pentacyclic core skeleton of isoschizogamine was described. Tetracyclic A,B,D,F-rings structure was assembled by intramolecular aza-Diels–Alder reaction via an ortho-iminoquinone methide intermediate. The C-ring was formed by oxidation of the benzylic position with a combination of Cr(CO)6 and t-BuOOH, followed by the introduction of an aminoethyl side chain, C–H oxidation of the lactam ring with CrO3 and n-Bu4NI, and final cyclization to construct the cyclic aminal moiety.
- Sugimoto, Kenji,Fujiwara, Hiroaki,Takada, Akihiro,Kim, Dong-Gil,Ueda, Hirofumi,Tokuyama, Hidetoshi
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p. 1028 - 1049
(2019/07/31)
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- Oxidative cyclizations in a nonpolar solvent using molecular oxygen and studies on the stereochemistry of oxypalladation
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Oxidative cyclizations of a variety of heteroatom nucleophiles onto unactivated olefins are catalyzed by palladium(II) and pyridine in the presence of molecular oxygen as the sole stoichiometric oxidant in a nonpolar solvent (toluene). Reactivity studies of a number of N-ligated palladium complexes show that chelating ligands slow the reaction. Nearly identical conditions are applicable to five different types of nucleophiles: phenols, primary alcohols, carboxylic acids, a vinylogous acid, and amides. Electronrich phenols are excellent substrates, and multiple olefin substitution patterns are tolerated. Primary alcohols undergo oxidative cyclization without significant oxidation to the aldehyde, a fact that illustrates the range of reactivity available from various Pd(II) salts under differing conditions. Alcohols can form both fused and spirocyclic ring systems, depending on the position of the olefin relative to the tethered alcohol; the same is true of the acid derivatives. The racemic conditions served as a platform for the development of an enantioselective reaction. Experiments with stereospecifically deuterated primary alcohol substrates rule out a "Wacker-type" mechanism involving anti oxypalladation and suggest that the reaction proceeds by syn oxypalladation for both mono- and bidentate ligands. In contrast, cyclizations of deuterium-labeled carboxylic acid substrates undergo anti oxypalladation.
- Trend, Raissa M.,Ramtohul, Yeeman K.,Stoltz, Brian M.
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p. 17778 - 17788
(2007/10/03)
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- Acid-Catalyzed Hydrolysis of Bridged Bi- and Tricyclic Compounds. XXVI. The Mechanisms of Formation of the Hydration Products of 2-Norbornen-5-one
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The acid-catalyzed hydration of 2-norbornen-5-one (1) in 5 mol dm-3 HClO4 at 358 K produces, according to GLC analyses, exo-5-hydroxy-2-norbornanone (2), 2-oxabicycloctan-3-one (3), which is in equilibrium with cis-3-hydroxycyclopentaneacetic acid (5), and 2-oxabicyclooctan-3-one (4).The former lactone (3) is unstable and rearranges slowly to the latter (4).The ketoalcohol (2) is formed via the slow protonation of norbornenone at C(3) and via subsequent hydration of the carbocation.The lactones are formed via complicated routes started by the protonation of norbornenone at C(2), and comprising 3- and 2-cyclopentaneacetic acid (7 and 9) as unstable intermediate products.
- Lajunen, Martti,Lahti, Marjo,Heimo, Satu
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p. 771 - 776
(2007/10/02)
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- Generation of Carbon-Carbon Double Bonds from β-Oxygenated Phenylseleno, Phenylthio, and Iodo Species. A New Use for the Chlorotrimethylsilane-Sodium Iodide Reagent
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A variety of β-oxygenated selenides, as exemplified by phenylseleno lactones, ethers, and alcohols are converted into olefins by treatment with Me3SiCl and NaI in MeCN; the reaction is stereospecific and can be extended to iodo and thio species.The conversion of 1,3, and 4 into 2-cyclopentene-1-acetic acid, of 5 into 2-(2-cyclopenten-1-yl)ethanol, and of 9 into (Z)-oct-4-ene illustrates the process.
- Clive, Derrick L.J.,Kale, Vilas N.
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p. 231 - 234
(2007/10/02)
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