- Reductive Difunctionalization of Aryl Alkenes with Sodium Metal and Reduction-Resistant Alkoxy-Substituted Electrophiles
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A general method for alkali-metal-promoted reductive difunctionalization of alkenes has been developed by means of reduction-resistant alkoxy-substituted electrophiles. A series of 1,2-diboration and 1,2-dicarbofunctionalization products can be synthesize
- Fukazawa, Mizuki,Nogi, Keisuke,Sasamori, Takahiro,Takahashi, Fumiya,Yorimitsu, Hideki
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supporting information
(2020/03/13)
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- Selective aliphatic carbon-hydrogen bond activation of protected alcohol substrates by cytochrome P450 enzymes
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Protected cyclohexanol and cyclohex-2-enol substrates, containing benzyl ether and benzoate ester moieties, were designed to fit into the active site of the Tyr96Ala mutant of cytochrome P450cam. The protected cyclohexanol substrates were efficiently and selectively hydroxylated by the mutant enzyme at the trans C-H bond of C-4 on the cyclohexyl ring. The selectivity of oxidation of the benzoate ester protected cyclohexanol could be altered by making alternative amino acid substitutions in the P450cam active site. The addition of the double bond in the cyclohexyl ring of the benzoate ester protected cyclohex-2-enol has a debilitative effect on the activity of the Tyr96Ala mutant with this substrate. However, the Phe87Ala/Tyr96Phe double mutant, which introduces space at a different location in the active site than the Tyr96Ala mutant, was able to efficiently hydroxylate the C-H bonds of 1-cyclohex-2-enyl benzoate at the allylic C-4 position. Mutations at Phe87 improved the selectivity of the oxidation of 1-phenyl-1-cyclohexylethylene to trans-4-phenyl-ethenylcyclohexanol (92%) when compared to single mutants at Tyr96 of P450cam. the Partner Organisations 2014.
- Bell, Stephen G.,Spence, Justin T. J.,Liu, Shenglan,George, Jonathan H.,Wong, Luet-Lok
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p. 2479 - 2488
(2014/04/03)
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- Pd-catalyzed allylic alkylation cascade with dihydropyrans: Regioselective synthesis of furo[3,2- c ]pyrans
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A regioselective palladium-catalyzed allylic alkylation cascade forms furo[3,2-c]pyrans from various cyclic β-dicarbonyl bis-nucleophiles and 3,6-dihydro-2H-pyran bis-electrophiles. The combination of allylic carbonate and anomeric siloxy leaving groups in the dihydropyran substrate allows control of the many regiochemical possibilities in this reaction. Annulation proceeds stereoconvergently to give cis-fused furopyrans from either cis- or trans-substituted starting material.
- Bartlett, Mark J.,Turner, Claire A.,Harvey, Joanne E.
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supporting information
p. 2430 - 2433
(2013/07/05)
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- Metal-free borylative ring-opening of vinyl epoxides and aziridines
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A rational approach towards the borylative ring-opening of vinylepoxides and vinylaziridines, by the in situ formed MeO-→bis(pinacolato) diboron adduct, has been developed. The enhanced nucleophilic character of the Bpin (sp2) moiety
- Sanz, Xavier,Lee, Graham M.,Pubill-Ulldemolins, Cristina,Bonet, Amadeu,Gulyas, Henrik,Westcott, Stephen A.,Bo, Carles,Fernandez, Elena
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p. 7004 - 7010
(2013/10/08)
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- Expanding the scope of biomass-derived chemicals through tandem reactions based on oxorhenium-catalyzed deoxydehydration
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New modes of DODH: Oxorhenium compounds act as deoxydehydration(DODH)/acid dual-purpose catalysts to transform biomass-derived diol substrates into a variety of commodity chemical precursors. The power of this approach is highlighted by a tandem [1,3]-OH shift/DODH of 2-ene-1,4-diols and 2,4-diene-1,6-diols, and by a DODH/esterification sequence of sugar acids to unsaturated esters for the production of polymers and plasticizers. Copyright
- Shiramizu, Mika,Toste, F. Dean
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supporting information
p. 12905 - 12909
(2014/01/06)
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- Synthesis of syn and anti 1,4-diols by copper-catalyzed boration of allylic epoxides
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Two sides of the same coin: Syn and anti 1,4-diols have been synthesized through the regio- and diastereoselective CuI-catalyzed boration of allylic epoxides (see scheme; pin=pinacolato, TES=triethylsilyl). In situ protection of the alcohol all
- Tortosa, Mariola
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p. 3950 - 3953
(2011/06/20)
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- Synthesis of 2-ene-1,4-diols by a new cascade-opening of 1,3-diepoxides: Towards an efficient synthesis of dihydroxytaxoid derivatives
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The synthesis of dihydroxytaxoid derivatives, specially 2-Ene-1,4-diols using a new cascade-opening of 1,3-diepoxides was investigated. The study prepared a framework through a cascade ring-closing dienyne metathesis (RCDEYM) reaction from Dienyne. The me
- Aldegunde, Maria J.,Castedo, Luis,Granja, Juan R.
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supporting information; experimental part
p. 4785 - 4787
(2009/12/09)
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- An efficient protocol for the enantioselective preparation of a key polyfunctionalized cyclohexane. New access to (R)- and (S)-4-hydroxy-2- cyclohexenone and (R)- and (S)-trans-cyclohex-2-ene-1,4-diol
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(Chemical Equation Presented) Starting from very accessible raw materials such as p-methoxyphenol, ethylene glycol, and thiophenol, a protocol has been developed to prepare multigram quantities of the polyfunctionalized cyclohexane (±)-7. A highly efficie
- Bayon, Pau,Marjanet, Georgina,Toribio, Gladis,Alibes, Ramon,De March, Pere,Figueredo, Marta,Font, Josep
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p. 3486 - 3491
(2008/09/21)
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- An efficient approach to either enantiomer of trans-cyclohex-2-ene-1,4-diol
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(1S,4S)-Cyclohex-2-ene-1,4-diol has been synthesised starting from a chiral p-benzoquinone equivalent. The sequence can be equally applied to the preparation of the (1R,4R)-enantiomer of the target diol.
- Alibes, Ramon,De March, Pedro,Figueredo, Marta,Font, Josep,Marjanet, Georgina
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p. 1151 - 1155
(2007/10/03)
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- Synthetic applications of functionalized silyl anions: Aminosilyl anions as hydroxy anion equivalent
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An (aminosilyl)lithium and the corresponding copper and magnesium reagents serve as a hydroxy anion equivalent through (1) allylic substitution, (2) addition to vinyloxirane, and (3) addition to acetylene, followed by oxidative cleavage of the silicon-carbon bonds. Highly regio- and stereoselective transformations have been achieved in all cases.
- Tamao, Kohei,Kawachi, Atsushi,Tanaka, Yoko,Ohtani, Hitoshi,Ito, Yoshihiko
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p. 5765 - 5772
(2007/10/03)
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- Stereo-and Regioselective Palladium-Catalyzed 1,4-Diacetoxylation of 1,3-Dienes
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Palladium-catalyzed oxidation of 1,3-dienes in acetic acid using an oxidation system of MnO2 and catalytic amounts of p-benzoquinone selectively gives 1,4-diacetoxy-2-alkenes.The reaction proceeds with high stereo-and regioselectivity, and by ligand control the reaction can be made to take place with either cis or trans 1,4-diacetoxylation across the diene in cyclic systems.Also in an acyclic system the 1,4-relative stereochemistry can be controlled as shown by the stereoselective oxidation of (E,E)- and (E,Z)-2,4-hexadiene to their corresponding dl (>88percent dl) and meso (>95percent meso) diacetates 15 and 18, respectively.Evidence is provided that supports a mechanism involving a trans acetoxypalladation of the conjugated diene to give an intermediate (?-allyl)palladium complex, followed by either a cis or trans attack by acetate on the allyl group.The cis attack is best explained by a cis migration from a (?-allyl)palladium intermediate.The diacetoxylation reaction was applied to the preparation of a key intermediate for the synthesis of dl-shikimic acid.
- Baeckvall, Jan-E.,Bystroem, Styrbjoern E.,Nordberg, Ruth E.
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p. 4619 - 4631
(2007/10/02)
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- Vinyl Epoxide Hydrolysis Reactions
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The rates of hydrolysis of cyclopentadiene oxide (3), cyclohexadiene oxide (4), cycloheptadiene oxide (5), cyclooctadiene oxide (6), butadiene oxide (7), and styrene oxide (8) have been determined as a function of pH.Each epoxide exhibited acid-catalyzed hydrolysis at low pH, and 3-5 showed significant rates for "spontaneous" reaction with solvent at intermediate pH values.The hydrolyses of several of the vinyl epoxides (4 and 5) showed kinetic terms in HO- at pH > ca. 13.Specific chloride effects attributed to nucleophilic addition of Cl- to neutral epoxide were observed for those compounds (3, 4, and 8) hydrolyzed in KCl solutions.From kinetic and product studies, mechanisms for hydrolyses of the vinyl epoxides are postulated.Acid-catalyzed hydrolyses of 3, 4, 5, and 6 were found to be A-1 in nature, proceeding via intermediate allyl cations.Product distributions depended on the structure of the cation.Mechanisms and product distributions for the spontaneous hydrolyses of vinyl epoxides were found to be variable, and dependent on the structure of the epoxide.
- Ross, Angela M.,Pohl, Terese M.,Piazza, Kathryn,Thomas, Michael,Fox, Bonnie,Whalen, Dale L.
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p. 1658 - 1665
(2007/10/02)
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