- Cu(OTf)2-catalyzed selective opening of aryl and vinyl epoxides with carbonyl compounds to give 1,3-dioxolanes
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Copper(II) triflate catalyzes the ring-opening of aryl- and vinyl-substituted epoxides with various carbonyl compounds to furnish 1,3-dioxolanes under mild conditions. Alkyl- and alkoxycarbonyl-substituted epoxides remain unchanged under reaction conditio
- Krasik, Pavel,Bohemier-Bernard, Mathieu,Yu, Qing
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- Carbohydrate/DBU Cocatalyzed Alkene Diboration: Mechanistic Insight Provides Enhanced Catalytic Efficiency and Substrate Scope
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A mechanistic investigation of the carbohydrate/DBU cocatalyzed enantioselective diboration of alkenes is presented. These studies provide an understanding of the origin of stereoselectivity and also reveal a strategy for enhancing reactivity and broadening the substrate scope.
- Yan, Lu,Meng, Yan,Haeffner, Fredrik,Leon, Robert M.,Crockett, Michael P.,Morken, James P.
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supporting information
p. 3663 - 3673
(2018/03/21)
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- Carbohydrate-Catalyzed Enantioselective Alkene Diboration: Enhanced Reactivity of 1,2-Bonded Diboron Complexes
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Catalytic enantioselective diboration of alkenes is accomplished with readily available carbohydrate-derived catalysts. Mechanistic experiments suggest the intermediacy of 1,2-bonded diboronates.
- Fang, Lichao,Yan, Lu,Haeffner, Fredrik,Morken, James P.
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supporting information
p. 2508 - 2511
(2016/03/12)
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- Scope and mechanism of the Pt-catalyzed enantioselective diboration of monosubstituted alkenes
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The Pt-catalyzed enantioselective diboration of terminal alkenes can be accomplished in an enantioselective fashion in the presence of chiral phosphonite ligands. Optimal procedures and the substrate scope of this transformation are fully investigated. Reaction progress kinetic analysis and kinetic isotope effects suggest that the stereodefining step in the catalytic cycle is olefin migratory insertion into a Pt-B bond. Density functional theory analysis, combined with other experimental data, suggests that the insertion reaction positions platinum at the internal carbon of the substrate. A stereochemical model for this reaction is advanced that is in line both with these features and with the crystal structure of a Pt-ligand complex.
- Coombs, John R.,Haeffner, Fredrik,Kliman, Laura T.,Morken, James P.
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supporting information
p. 11222 - 11231
(2013/08/23)
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- Modular monodentate oxaphospholane ligands: Utility in highly efficient and enantioselective 1,4-diboration of 1,3-dienes
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Tune it up! Tunable, chiral, monodentate oxaphospholane ligands (termed OxaPhos) are highly effective in the Pt-catalyzed title reaction, providing the 1,4-addition products in enantiomer ratios approaching 99:1 (see scheme). In the presence of enantiomerically pure cis-iBu-OxaPhos, a catalyst loading of only 0.02 mol% [Pt(dba)3] was sufficient for effective reaction. pin=pinacolato, dba=dibenzylideneacetone.
- Schuster, Christopher H.,Li, Bo,Morken, James P.
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supporting information; scheme or table
p. 7906 - 7909
(2011/10/09)
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- Asymmetric 1,4-dihydroxylation of 1,3-dienes by catalytic enantioselective diboration
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(Chemical Equation Presented) Asymmetric 1,4-dihydroxylations of 1,3-dienes, and other transformations, are initiated by the Pt-catalyzed enantioselective addition of bis(pinacolato)diboron (B2(pin) 2) to conjugated dienes. The studies reported in this communication suggest that both cyclic and acyclic substrates will participate in this reaction; however, dienes which are unable to adopt the S-cis conformation are unreactive. For most substrates, 1,4-addition is the predominant pathway. In addition to oxidation to the derived 2-buten-1,4-diol, stereoselective carbonyl allylation with the intermediate bis(boronate) ester is also described.
- Burks, Heather E.,Kliman, Laura T.,Morken, James P.
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supporting information; experimental part
p. 9134 - 9135
(2009/12/05)
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- ZrCl4 as an efficient catalyst for a novel one-pot protection/deprotection synthetic methodology
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(Chemical Equation Presented) A catalytic quantity of ZrCl4 (20 mol %) was found to be an efficient catalyst for the one-pot esterification and deprotection of (5S,6R)-5,6-diacetoxyoct-7-enoic acid in good yields (44-62%) with a lactone formed as a minor byproduct. ZrCl4 (10-20 mol %) was also sufficient to deprotect 1,3-dioxalane, bis-TBDMS ethers, and diacetate functional groups in excellent yields of up to 93%. ZrCl4 (1-10 mol %) also promoted diol protection as the acetonide in 90% yield and acted as a trans-esterification catalyst for a range of esters.
- Singh, Surendra,Duffy, Colm D.,Shah, Syed Tasadaque A.,Guiry, Patrick J.
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p. 6429 - 6432
(2008/12/22)
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- Self-assembled nanoreactors as highly active catalysts in the hydrolytic kinetic resolution (HKR) of epoxides in water
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CoIII(salen) complexes have been immobilized on amphiphilic block copolymers, which self-assemble in water to give micellar aggregates with a hydrophobic Co(salen) core and a water-soluble shell (see picture). These aggregates were used to catalyze the hydrolytic kinetic resolution (HKR) of racemic aromatic epoxides over four consecutive cycles and gave the epoxides in up to 99 % ee. H2salen = N,N′-bis(salicylidene)ethylenediamine. (Chemical Equation Presented).
- Rossbach, Benjamin M.,Leopold, Kerstin,Weberskirch, Ralf
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p. 1309 - 1312
(2007/10/03)
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- ANALYTICAL ENANTIOMER SEPARATION OF ALIPHATIC DIOLS AS BORONATES AND ACETALS BY COMPLEXATION GAS CHROMATOGRAPHY
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Cyclic boronates and acetals of mono- and dialkylsubstituted 1,2-, 2,3- 1,3-and 1,4-diols have been quantitatively separated into enantiomers by complexation gas chromatography utilizing optically active metal chelates.An efficient, precise and sensitive method for determining enantiomeric purities for volatile glycols is thus available.
- Schurig, V.,Wistuba, D.
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p. 5633 - 5636
(2007/10/02)
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