scholarly journals Rhodium-catalyzed regioselective addition of thioacids to terminal allenes: enantioselective access to branched allylic thioesters

2022 ◽  
Author(s):  
A. Ziyaei Halimehjani ◽  
B. Breit
Keyword(s):  
Catalyst System ◽  
Regioselective Addition ◽  
Enantioselective Addition

Regioselective and enantioselective addition of thioacids to terminal allenes is reported employing a rhodium(i)/DIOP catalyst system. Complete catalyst control of diastereoselectivity was achieved upon addition of chiral amino thioacids to allenes.

Establishing Arrays of Stereogenic Centers: The Sato/Chida Synthesis of (-)-Kainic Acid

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Catalyst System ◽  
Allylic Alcohol ◽  
University Of Pennsylvania ◽  
Ni Catalyst ◽  
Max Planck ◽  
Stereogenic Centers ◽  
University College London ◽  
Enantioselective Addition ◽  
La Jolla ◽  
The University

Benjamin List of the Max-Planck-Institut, Mülheim, devised (J. Am. Chem. Soc. 2010, 132, 10227) a catalyst system for the stereocontrolled epoxidation of a trisubstituted alkenyl aldehyde 1. Takashi Ooi of Nagoya University effected (Angew. Chem. Int. Ed. 2010, 49, 7562; see also Org. Lett. 2010, 12, 4070) enantioselective Henry addition to an alkynyl aldehyde 3. Madeleine M. Joullié of the University of Pennsylvania showed (Org. Lett. 2010, 12, 4244) that an amine 7 added selectively to an alkynyl aziridine 6. Yutaka Ukaji and Katsuhiko Inomata of Kanazawa University developed (Chem. Lett. 2010, 39, 1036) the enantioselective dipolar cycloaddition of 9 with 10. K. C. Nicolaou of Scripps/La Jolla observed (Angew. Chem. Int. Ed. 2010, 49, 5875; see also J. Org. Chem. 2010, 75, 8658) that the allylic alcohol from enantioselective reduction of 12 could be hydrogenated with high diastereocontrol. Masamichi Ogasawara and Tamotsu Takahashi of Hokkaido University added (Org. Lett. 2010, 12, 5736) the allene 14 to the acetal 15 with substantial stereocontrol. Helen C. Hailes of University College London investigated (Chem. Comm. 2010, 46, 7608) the enzyme-mediated addition of 18 to racemic 17. Dawei Ma of the Shanghai Institute of Organic Chemistry, in the course of a synthesis of oseltamivir (Tamiflu), accomplished (Angew. Chem. Int. Ed. 2010, 49, 4656) the enantioselective addition of 21 to 20. Shigeki Matsunaga of the University of Tokyo and Masakatsu Shibasaki of the Institute of Microbial Chemistry developed (Org. Lett. 2010, 12, 3246) a Ni catalyst for the enantioselective addition of 23 to 24. Juthanat Kaeobamrung and Jeffrey W. Bode of ETH-Zurich and Marisa C. Kozlowski of the University of Pennsylvania devised (Proc. Natl. Acad. Sci. 2010, 107, 20661) an organocatalyst for the enantioselective addition of 27 to 26. Yihua Zhang of China Pharmaceutical University and Professor Ma effected (Tetrahedron Lett. 2010, 51, 3827) the related addition of 27 to 29. There have been scattered reports on the stereochemical course of the coupling of cyclic secondary organometallics. In a detailed study, Paul Knochel of Ludwig-Maximilians- Universität München showed (Nat. Chem. 2020, 2, 125) that equatorial bond formation dominated, exemplified by the conversion of 31 to 33.

Highly enantioselective addition of terminal alkynes to aldehydes catalyzed by a new chiral β-sulfonamide alcohol/Ti(OiPr)4/Et2Zn/R3N catalyst system

Chirality ◽  
2009 ◽  
Vol 21 (2) ◽  
pp. 316-323 ◽  
Author(s):  
Li Qiu ◽  
Quan Wang ◽  
Li Lin ◽  
Xiaodong Liu ◽  
Xianxing Jiang ◽  
...  
Keyword(s):  
Catalyst System ◽  
Terminal Alkynes ◽  
Enantioselective Addition

Enantioselective Preparation of Alcohols and Amines

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Enantioselective Hydrogenation ◽  
Catalyst System ◽  
Hydroxy Ketone ◽  
Boston College ◽  
Princeton University ◽  
Terminal Alkene ◽  
Tokyo Institute ◽  
Enantioselective Addition ◽  
Institute Of Technology ◽  
The University

Renat Kadyrov of Evonik Degussa and Magnus Rueping of RWTH Aachen developed (Angew. Chem. Int. Ed. 2009, 49, 7556) an effective catalyst for the enantioselective hydrogenation of an α-hydroxy ketone 1 to the 1,2-diol 2 . Yong-Gui Zhou of the Dalian Institute of Chemical Physics showed (J. Org. Chem. 2009, 74, 5633) that a sultam such as 3 could be reduced with high ee to the sulfonamide 4. They also used this same approach to prepare both α-aryl and α,α-diaryl amines. David W. C. MacMillan of Princeton University described (Angew. Chem. Int. Ed. 2009, 49, 5121) the optimized enantioselective α-chlorination of an aldehyde 5 and the direct processing of the product to the epoxide 6. Erick M. Carreira of ETH Zürich reported (Synlett 2009, 2076) an alternative route to high ee epoxides by decarbonylation of an epoxy aldehyde 7. James P. Morken of Boston College established (J. Am. Chem. Soc. 2009, 131, 13210) a procedure for the enantioselective bis borylation of a terminal alkene 9, leading after oxidation to the 1,2-diol 10. Ben L. Feringa of the University of Groningen took advantage (J. Am. Chem. Soc. 2009, 131, 9473) of their alternative Wacker conditions to convert a primary allylic carbonate 11 to the protected β-amino aldehyde 12. Chao-Shan Da of Lanzhou University devised (Organic Lett. 2009, 11, 5578) additives that allow the direct enantioselective addition of a Grignard reagent 14 to an aldehyde. The enantioselective addition of substituted ketenes to aldehydes has long been established. Yun-Ming Lin of the University of Toledo developed (Synlett 2009, 1675) a catalyst system for the enantioselective addition of ketene 17 itself. An alkenyl silane 19 can readily be prepared from the corresponding terminal alkene (J. Org. Chem. 2010, 75, 1701). Koichi Mikami of the Tokyo Institute of Technology showed (J. Am. Chem. Soc. 2009, 131, 13922) that such alkenyl silanes add to ethyl glyoxylate 20 with high ee. Amir H. Hoveyda of Boston College devised (J. Am. Chem. Soc. 2009, 131, 18234) a procedure for the enantioselective conversion of a terminal alkyne 22 to the 1,2-bis boryl alkane, which he took on directly to the coupled product 24.

Regio-, Stereo- and Enantioselective α-Addition of Carbonyl Nucleo-philes to Allenamides Catalyzed by a Synergistic Copper/Enamine System

2020 ◽  
Author(s):  
Rémi Blieck ◽  
Sebastien Lemouzy ◽  
Marc Taillefer ◽  
Florian Monnier
Keyword(s):  
Catalytic System ◽  
Secondary Amine ◽  
Primary Amine ◽  
Synergistic Catalysis ◽  
Enantioselective Addition ◽  
Amine Catalysts

A dual copper/enamine catalytic system is found to enable an intermolecular enantioselective α-addition of various carbonyl nucleophiles to allenamides. Secondary amine catalysts allowed the highly enantioselective addition of aldehydes, while using primary amine catalysts led to the enantioselective addition of ketoester nucleophiles. The process was found to be highly regio-, stereo- and enantio-selective and represented the first allene hydrofunctionalization using an synergistic catalysis involving copper

Direct Observation of Chain Lengths and Conformations in Oligofluorene Distributions from Controlled Polymerization by Double Electron-Electron Resonance

2019 ◽  
Author(s):  
Dennis Bücker ◽  
Annika Sickinger ◽  
Julian D. Ruiz Perez ◽  
Manuel Oestringer ◽  
Stefan Mecking ◽  
...  
Keyword(s):  
Chain Length ◽  
Length Distribution ◽  
Catalyst System ◽  
Chain Conformation ◽  
Controlled Polymerization ◽  
Chain Length Distribution ◽  
Electron Resonance ◽  
Double Electron ◽  
The Individual ◽  
Double Electron Electron Resonance

Synthetic polymers are mixtures of different length chains, and their chain length and chain conformation is often experimentally characterized by ensemble averages. We demonstrate that Double-Electron-Electron-Resonance (DEER) spectroscopy can reveal the chain length distribution, and chain conformation and flexibility of the individual n-mers in oligo-(9,9-dioctylfluorene) from controlled Suzuki-Miyaura Coupling Polymerization (cSMCP). The required spin-labeled chain ends were introduced efficiently via a TEMPO-substituted initiator and chain terminating agent, respectively, with an in situ catalyst system. Individual precise chain length oligomers as reference materials were obtained by a stepwise approach. Chain length distribution, chain conformation and flexibility can also be accessed within poly(fluorene) nanoparticles.

Mechanistic Insights into Fe Catalyzed α-C-H Oxidations of Tertiary Amines

2019 ◽  
Author(s):  
Christopher J. Legacy ◽  
Frederick T. Greenaway ◽  
Marion Emmert
Keyword(s):  
Free Radical ◽  
Catalytic Mechanism ◽  
Catalyst System ◽  
Oxidation Products ◽  
Tertiary Amines ◽  
Catalyst Activation ◽  
Rate Determining Step ◽  
Fe Catalyst ◽  
Ligand Coordination ◽  
Rate Kinetics

We report detailed mechanistic investigations of an iron-based catalyst system, which allows the α-C-H oxidation of a wide variety of amines, including acyclic tertiary aliphatic amines, to afford dealkylated or amide products. In contrast to other catalysts that affect α-C-H oxidations of tertiary amines, the system under investigation employs exclusively peroxy esters as oxidants. More common oxidants (e.g. tBuOOH) previously reported to affect amine oxidations via free radical pathways do not provide amine α-C-H oxidation products in combination with the herein described catalyst system. Motivated by this difference in reactivity to more common free radical systems, the investigations described herein employ initial rate kinetics, kinetic profiling, Eyring studies, kinetic isotope effect studies, Hammett studies, ligand coordination studies, and EPR studies to shed light on the Fe catalyst system. The obtained data suggest that the catalytic mechanism proceeds through C-H abstraction at a coordinated substrate molecule. This rate-determining step occurs either at an Fe(IV) oxo pathway or a 2-electron pathway at a Fe(II) intermediate with bound oxidant. We further show via kinetic profiling and EPR studies that catalyst activation follows a radical pathway, which is initiated by hydrolysis of PhCO3 tBu to tBuOOH in the reaction mixture. Overall, the obtained mechanistic data support a non-classical, Fe catalyzed pathway that requires substrate binding, thus inducing selectivity for α-C-H functionalization.<br>

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