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Tönjes J, Kell L, Werner T. Organocatalytic Stereospecific Appel Reaction. Org Lett 2023; 25:9114-9118. [PMID: 38113448 DOI: 10.1021/acs.orglett.3c03463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2023]
Abstract
Herein we report a new method for the catalytic Appel reaction by P(III)/P(V) redox cycling at very low catalyst loadings of 1-2 mol % using low amounts of hexachloroacetone as the halogen source and phenylsilane as the terminal reductant. Twenty-six alcohols and nine epoxides containing a wide variety of functional groups were converted to the respective chlorides and dichlorides in yields of up to 97%, enantiospecificities of up to >99%, and enantiomeric ratios of up to >99:1.
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Affiliation(s)
- Jan Tönjes
- Leibniz Institute for Catalysis at the University of Rostock (LIKAT Rostock), Albert-Einstein-Str. 29a, 18059 Rostock, Germany
| | - Lukas Kell
- Leibniz Institute for Catalysis at the University of Rostock (LIKAT Rostock), Albert-Einstein-Str. 29a, 18059 Rostock, Germany
| | - Thomas Werner
- Leibniz Institute for Catalysis at the University of Rostock (LIKAT Rostock), Albert-Einstein-Str. 29a, 18059 Rostock, Germany
- Department of Chemistry and Center for Sustainable Systems Design (CSSD), Paderborn University, Warburger Str. 100, 33098 Paderborn, Germany
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2
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Chugunova E, Gazizov AS, Islamov D, Matveeva V, Burilov A, Akylbekov N, Dobrynin A, Zhapparbergenov R, Appazov N, Chabuka BK, Christopher K, Tonkoglazova DI, Alabugin IV. An Unusual Rearrangement of Pyrazole Nitrene and Coarctate Ring-Opening/Recyclization Cascade: Formal CH-Acetoxylation and Azide/Amine Conversion without External Oxidants and Reductants. Molecules 2023; 28:7335. [PMID: 37959754 PMCID: PMC10648078 DOI: 10.3390/molecules28217335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2023] [Revised: 10/20/2023] [Accepted: 10/26/2023] [Indexed: 11/15/2023] Open
Abstract
We report an unusual transformation where the transient formation of a nitrene moiety initiates a sequence of steps leading to remote oxidative C-H functionalization (R-CH3 to R-CH2OC(O)R') and the concomitant reduction of the nitrene into an amino group. No external oxidants or reductants are needed for this formal molecular comproportionation. Detected and isolated intermediates and computational analysis suggest that the process occurs with pyrazole ring opening and recyclization.
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Affiliation(s)
- Elena Chugunova
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Akad. Arbuzov St. 8, Kazan 420088, Russia; (A.S.G.); (D.I.); (V.M.); (A.B.); (A.D.); (I.V.A.)
| | - Almir S. Gazizov
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Akad. Arbuzov St. 8, Kazan 420088, Russia; (A.S.G.); (D.I.); (V.M.); (A.B.); (A.D.); (I.V.A.)
| | - Daut Islamov
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Akad. Arbuzov St. 8, Kazan 420088, Russia; (A.S.G.); (D.I.); (V.M.); (A.B.); (A.D.); (I.V.A.)
| | - Victoria Matveeva
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Akad. Arbuzov St. 8, Kazan 420088, Russia; (A.S.G.); (D.I.); (V.M.); (A.B.); (A.D.); (I.V.A.)
| | - Alexander Burilov
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Akad. Arbuzov St. 8, Kazan 420088, Russia; (A.S.G.); (D.I.); (V.M.); (A.B.); (A.D.); (I.V.A.)
| | - Nurgali Akylbekov
- Laboratory of Engineering Profile “Physical and Chemical Methods of Analysis”, Korkyt Ata Kyzylorda University, Aitekebie Str. 29A, Kyzylorda 120014, Kazakhstan; (N.A.); (R.Z.)
| | - Alexey Dobrynin
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Akad. Arbuzov St. 8, Kazan 420088, Russia; (A.S.G.); (D.I.); (V.M.); (A.B.); (A.D.); (I.V.A.)
| | - Rakhmetulla Zhapparbergenov
- Laboratory of Engineering Profile “Physical and Chemical Methods of Analysis”, Korkyt Ata Kyzylorda University, Aitekebie Str. 29A, Kyzylorda 120014, Kazakhstan; (N.A.); (R.Z.)
| | - Nurbol Appazov
- Laboratory of Engineering Profile “Physical and Chemical Methods of Analysis”, Korkyt Ata Kyzylorda University, Aitekebie Str. 29A, Kyzylorda 120014, Kazakhstan; (N.A.); (R.Z.)
- Zhakhaev Kazakh Scientific Research Institute of Rice Growing, Abay Av. 25B, Kyzylorda 120008, Kazakhstan
| | - Beauty K. Chabuka
- Department of Chemistry and Biochemistry, Florida State University, 95 Chieftan Way, Tallahassee, FL 32306-3290, USA; (B.K.C.); (K.C.); (D.I.T.)
| | - Kimberley Christopher
- Department of Chemistry and Biochemistry, Florida State University, 95 Chieftan Way, Tallahassee, FL 32306-3290, USA; (B.K.C.); (K.C.); (D.I.T.)
| | - Daria I. Tonkoglazova
- Department of Chemistry and Biochemistry, Florida State University, 95 Chieftan Way, Tallahassee, FL 32306-3290, USA; (B.K.C.); (K.C.); (D.I.T.)
| | - Igor V. Alabugin
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Akad. Arbuzov St. 8, Kazan 420088, Russia; (A.S.G.); (D.I.); (V.M.); (A.B.); (A.D.); (I.V.A.)
- Department of Chemistry and Biochemistry, Florida State University, 95 Chieftan Way, Tallahassee, FL 32306-3290, USA; (B.K.C.); (K.C.); (D.I.T.)
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3
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Qiu X, Brückel J, Zippel C, Nieger M, Biedermann F, Bräse S. Tris(4-azidophenyl)methanol - a novel and multifunctional thiol protecting group. RSC Adv 2023; 13:2483-2486. [PMID: 36741178 PMCID: PMC9844210 DOI: 10.1039/d2ra05997e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Accepted: 12/21/2022] [Indexed: 01/19/2023] Open
Abstract
The novel tris(4-azidophenyl)methanol, a multifunctionalisable aryl azide, is reported. The aryl azide can be used as a protecting group for thiols in peptoid synthesis and can be cleaved under mild reaction conditions via a Staudinger reduction. Moreover, the easily accessible aryl azide can be functionalised via copper-catalysed cycloaddition reactions, providing additional opportunities for materials chemistry applications.
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Affiliation(s)
- Xujun Qiu
- Institute of Organic Chemistry (IOC), Karlsruhe Institute of Technology (KIT)Fritz-Haber-Weg 676131 KarlsruheGermany(+49)-721-6084-2903
| | - Julian Brückel
- Institute of Organic Chemistry (IOC), Karlsruhe Institute of Technology (KIT)Fritz-Haber-Weg 676131 KarlsruheGermany(+49)-721-6084-2903
| | - Christoph Zippel
- Institute of Organic Chemistry (IOC), Karlsruhe Institute of Technology (KIT)Fritz-Haber-Weg 676131 KarlsruheGermany(+49)-721-6084-2903
| | - Martin Nieger
- Department of Chemistry, University of HelsinkiP. O. Box 55 (A. I. Virtasen aukio 1)00014Finland
| | - Frank Biedermann
- Karlsruhe Institute of Technology (KIT), Institute of Nanotechnology (INT)Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-LeopoldshafenGermany
| | - Stefan Bräse
- Institute of Organic Chemistry (IOC), Karlsruhe Institute of Technology (KIT)Fritz-Haber-Weg 676131 KarlsruheGermany(+49)-721-6084-2903,Institute of Biological and Chemical Systems – Functional Molecular Systems (IBCS-FMS), Karlsruhe Institute of Technology (KIT)Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-LeopoldshafenGermany
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4
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Pei M, Tian A, Yang Q, Huang N, Wang L, Li D. Organophosphorus catalytic reaction based on reduction of phosphine oxide. GREEN SYNTHESIS AND CATALYSIS 2022. [DOI: 10.1016/j.gresc.2022.10.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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5
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Borthakur I, Maji M, Joshi A, Kundu S. Reductive Alkylation of Azides and Nitroarenes with Alcohols: A Selective Route to Mono- and Dialkylated Amines. J Org Chem 2021; 87:628-643. [PMID: 34898200 DOI: 10.1021/acs.joc.1c02625] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Herein, we demonstrated an efficient protocol for reductive alkylation of azides/nitro compounds via a borrowing hydrogen (BH) method. By following this protocol, selective mono- and dialkylated amines were obtained under mild and solvent-free conditions. A series of control experiments and deuterium-labeling experiments were performed to understand this catalytic process. Mechanistic studies suggested that the Ir(III)-H was the active intermediate in this reaction. KIE study revealed that the breaking of the C-H bond of alcohol might be the rate-limiting step. Notably, this solvent-free strategy disclosed a high TON of around 5600. Based on kinetic studies and control experiments, a metal-ligand cooperative mechanism was proposed.
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Affiliation(s)
- Ishani Borthakur
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, Uttar Pradesh (U.P.), India
| | - Milan Maji
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, Uttar Pradesh (U.P.), India
| | - Abhisek Joshi
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, Uttar Pradesh (U.P.), India
| | - Sabuj Kundu
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, Uttar Pradesh (U.P.), India
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6
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Trejo-Maldonado M, Elizalde LE, Le Droumaguet B, Grande D. Synthesis of triazole-functionalized diblock copolymers as templates for porous materials. REACT FUNCT POLYM 2021. [DOI: 10.1016/j.reactfunctpolym.2021.104919] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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7
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Xie C, Smaligo AJ, Song XR, Kwon O. Phosphorus-Based Catalysis. ACS CENTRAL SCIENCE 2021; 7:536-558. [PMID: 34056085 PMCID: PMC8155461 DOI: 10.1021/acscentsci.0c01493] [Citation(s) in RCA: 116] [Impact Index Per Article: 38.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Indexed: 05/08/2023]
Abstract
Phosphorus-based organocatalysis encompasses several subfields that have undergone rapid growth in recent years. This Outlook gives an overview of its various aspects. In particular, we highlight key advances in three topics: nucleophilic phosphine catalysis, organophosphorus catalysis to bypass phosphine oxide waste, and organophosphorus compound-mediated single electron transfer processes. We briefly summarize five additional topics: chiral phosphoric acid catalysis, phosphine oxide Lewis base catalysis, iminophosphorane super base catalysis, phosphonium salt phase transfer catalysis, and frustrated Lewis pair catalysis. Although it is not catalytic in nature, we also discuss novel discoveries that are emerging in phosphorus(V) ligand coupling. We conclude with some ideas about the future of organophosphorus catalysis.
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Affiliation(s)
- Changmin Xie
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Andrew J. Smaligo
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | | | - Ohyun Kwon
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
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8
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Lipshultz JM, Li G, Radosevich AT. Main Group Redox Catalysis of Organopnictogens: Vertical Periodic Trends and Emerging Opportunities in Group 15. J Am Chem Soc 2021; 143:1699-1721. [PMID: 33464903 PMCID: PMC7934640 DOI: 10.1021/jacs.0c12816] [Citation(s) in RCA: 117] [Impact Index Per Article: 39.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A growing number of organopnictogen redox catalytic methods have emerged-especially within the past 10 years-that leverage the plentiful reversible two-electron redox chemistry within Group 15. The goal of this Perspective is to provide readers the context to understand the dramatic developments in organopnictogen catalysis over the past decade with an eye toward future development. An exposition of the fundamental differences in the atomic structure and bonding of the pnictogens, and thus the molecular electronic structure of organopnictogen compounds, is presented to establish the backdrop against which organopnictogen redox reactivity-and ultimately catalysis-is framed. A deep appreciation of these underlying periodic principles informs an understanding of the differing modes of organopnictogen redox catalysis and evokes the key challenges to the field moving forward. We close by addressing forward-looking directions likely to animate this area in the years to come. What new catalytic manifolds can be developed through creative catalyst and reaction design that take advantage of the intrinsic redox reactivity of the pnictogens to drive new discoveries in catalysis?
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Affiliation(s)
- Jeffrey M Lipshultz
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Gen Li
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Alexander T Radosevich
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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9
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Shaik MS, Nadiveedhi MR, Gundluru M, Sarva S, Allagadda R, Chippada AR, Chamarthi N, Cirandur SR. Green synthesis of phosphoramidates and evaluation of their α-amylase activity by in silico and in vitro studies. SYNTHETIC COMMUN 2021. [DOI: 10.1080/00397911.2021.1876239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
| | | | - Mohan Gundluru
- Department of Chemistry, Sri Venkateswara University, Tirupati, AP, India
- DST–PURSE Centre, Sri Venkateswara University, Tirupati, AP, India
| | - Santhisudha Sarva
- Department of Chemistry, Sri Venkateswara University, Tirupati, AP, India
| | | | - Appa Rao Chippada
- Department of Biochemistry, Sri Venkateswara University, Tirupati, AP, India
| | - Nagaraju Chamarthi
- Department of Chemistry, Sri Venkateswara University, Tirupati, AP, India
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10
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Zeng Z, Liu S, Luo W, Liang J, Peng A. Efficient Synthesis of Phosphorus/Nitrogen‐Containing Chrysin Derivatives via Classic Reactions. ChemistrySelect 2021. [DOI: 10.1002/slct.202004358] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Ziyi Zeng
- School of Chemistry Sun Yat-sen University 135 Xingangxi Lu Guangzhou China
| | - Shuang Liu
- School of Chemistry Sun Yat-sen University 135 Xingangxi Lu Guangzhou China
| | - Wenjun Luo
- School of Chemistry Sun Yat-sen University 135 Xingangxi Lu Guangzhou China
| | - Jiaxin Liang
- School of Chemistry Sun Yat-sen University 135 Xingangxi Lu Guangzhou China
| | - Ai‐Yun Peng
- School of Chemistry Sun Yat-sen University 135 Xingangxi Lu Guangzhou China
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12
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Aldrich CC, Buonomo JA, Cole MS, Eiden CG. 1,3-Diphenyldisiloxane Enables Additive-Free Redox Recycling Reactions and Catalysis with Triphenylphosphine. SYNTHESIS-STUTTGART 2020. [DOI: 10.1055/s-0040-1707345] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The recently reported chemoselective reduction of phosphine oxides with 1,3-diphenyldisiloxane (DPDS) has opened up the possibility of additive-free phosphine oxide reductions in catalytic systems. Herein we disclose the use of this new reducing agent as an enabler of phosphorus redox recycling in Wittig, Staudinger, and alcohol substitution reactions. DPDS was successfully utilized in ambient-temperature additive-free redox recycling variants of the Wittig olefination, Appel halogenation, and Staudinger reduction. Triphenylphosphine-promoted catalytic recycling reactions were also facilitated by DPDS. Additive-free triphenylphosphine-promoted catalytic Staudinger reductions could even be performed at ambient temperature due to the rapid nature of phosphinimine reduction, for which we characterized kinetic and thermodynamic parameters. These results demonstrate the utility of DPDS as an excellent reducing agent for the development of phosphorus redox recycling reactions.
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Geeson M, Cummins CC. Let's Make White Phosphorus Obsolete. ACS CENTRAL SCIENCE 2020; 6:848-860. [PMID: 32607432 PMCID: PMC7318074 DOI: 10.1021/acscentsci.0c00332] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Indexed: 05/20/2023]
Abstract
Industrial and laboratory methods for incorporating phosphorus atoms into molecules within the framework of Green Chemistry are in their infancy. Current practice requires large inputs of energy, involves toxic intermediates, and generates substantial waste. Furthermore, a negligible fraction of phosphorus-containing waste is recycled which in turn contributes to negative environmental impacts, such as eutrophication. Methods that begin to address some of these drawbacks are reviewed, and some key opportunities to be realized by pursuing organophosphorus chemistry under the principles of Green Chemistry are highlighted. Methods used by nature, or in the chemistry of other elements such as silicon, are discussed as model processes for the future of phosphorus in chemical synthesis.
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Liu R, Wei Z, Wang J, Liu Y, Xue H. Highly selective hydrosilylation of equilibrating allylic azides. Chem Commun (Camb) 2020; 56:5038-5041. [PMID: 32242569 DOI: 10.1039/d0cc01316a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The Pt-catalyzed hydrosilylation of equilibrating allylic azides is reported. The reaction provides only one out of four possible hydrosilylation products in good yields and with very high chemoselectivity (alk-1-ene vs. alk-2-ene), regioselectivity (linear vs. branched), and excellent functional group tolerance.
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Affiliation(s)
- Ruzhang Liu
- College of Chemistry & Chemical Engineering, Yangzhou University, 180 Siwangting Rd., Yangzhou 225002, China.
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15
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Longwitz L, Werner T. Reduction of Activated Alkenes by P
III
/P
V
Redox Cycling Catalysis. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201912991] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Lars Longwitz
- OrganocatalysisLeibniz-Institute for Catalysis Albert-Einstein-Straße 29a Rostock Germany
| | - Thomas Werner
- OrganocatalysisLeibniz-Institute for Catalysis Albert-Einstein-Straße 29a Rostock Germany
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Longwitz L, Werner T. Reduction of Activated Alkenes by P III /P V Redox Cycling Catalysis. Angew Chem Int Ed Engl 2020; 59:2760-2763. [PMID: 31793147 PMCID: PMC7027467 DOI: 10.1002/anie.201912991] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 11/18/2019] [Indexed: 01/09/2023]
Abstract
The carbon-carbon double bond of unsaturated carbonyl compounds was readily reduced by using a phosphetane oxide catalyst in the presence of a simple organosilane as the terminal reductant and water as the hydrogen source. Quantitative hydrogenation was observed when 1.0 mol % of a methyl-substituted phosphetane oxide was employed as the catalyst. The procedure is highly selective towards activated double bonds, tolerating a variety of functional groups that are usually prone to reduction. In total, 25 alkenes and two alkynes were hydrogenated to the corresponding alkanes in excellent yields of up to 99 %. Notably, less active poly(methylhydrosiloxane) could also be utilized as the terminal reductant. Mechanistic investigations revealed the phosphane as the catalyst resting state and a protonation/deprotonation sequence as the crucial step in the catalytic cycle.
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Affiliation(s)
- Lars Longwitz
- Organocatalysis, Leibniz-Institute for Catalysis, Albert-Einstein-Straße 29a, Rostock, Germany
| | - Thomas Werner
- Organocatalysis, Leibniz-Institute for Catalysis, Albert-Einstein-Straße 29a, Rostock, Germany
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Convergent Synthesis of Polysubstituted Furans via Catalytic Phosphine Mediated Multicomponent Reactions. Molecules 2019; 24:molecules24244595. [PMID: 31888142 PMCID: PMC6943692 DOI: 10.3390/molecules24244595] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 12/10/2019] [Accepted: 12/13/2019] [Indexed: 11/29/2022] Open
Abstract
Tri- or tetrasubstituted furans have been prepared from terminal activated olefins and acyl chlorides or anhydrides by a multicomponental convergent synthesis mode. Instead of stoichiometric nBu3P, only catalytic nBu3P or nBu3P=O is needed to furnish the furans in modest to excellent yields with a good functional group tolerance under the aid of reducing agent silane. This synthetic method features a silane-driven catalytic intramolecular Wittig reaction as a key annulation step and represents the first successful application of catalytic Wittig reaction in multicomponent cascade reaction.
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