skip to main content

Explore Research Products in the NSF-PAR

Title: Recent advances in oxidative allylic C–H functionalization via group IX-metal catalysis
Allylic substitution, pioneered by the work of Tsuji and Trost, has been an invaluable tool in the synthesis of complex molecules for decades. An attractive alternative to allylic substitution is the direct functionalization of allylic C–H bonds of unactivated alkenes, thereby avoiding the need for prefunctionalization. Significant early advances in allylic C–H functionalization were made using palladium catalysis. However, Pd-catalyzed reactions are generally limited to the functionalization of terminal olefins with stabilized nucleophiles. Insights from Li, Cossy, and Tanaka demonstrated the utility of RhCp x catalysts for allylic functionalization. Since these initial reports, a number of key intermolecular Co-, Rh-, and Ir-catalyzed allylic C–H functionalization reactions have been reported, offering significant complementarity to the Pd-catalyzed reactions. Herein, we report a summary of recent advances in intermolecular allylic C–H functionalization via group IX-metal π-allyl complexes. Mechanism-driven development of new catalysts is highlighted, and the potential for future developments is discussed.  more » « less
Award ID(s):
1700982
NSF-PAR ID:
10234859
Author(s) / Creator(s):
; ;
Date Published:
Journal Name:
Chemical Communications
Volume:
56
Issue:
87
ISSN:
1359-7345
Page Range / eLocation ID:
13287 to 13300
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ( , Dalton Transactions)
    null (Ed.)
    Allylic C–H functionalization catalysed by group 9 Cp* transition-metal complexes has recently gained significant attention. These reactions have expanded allylic C–H functionalization to include di- and trisubstituted olefins, and a broad range of coupling partners. More specifically, several catalytic C–N, C–O, and C–C bond forming allylic C–H functionalization reactions have been reported, proceeding via MCp*-π-allyl intermediates. Herein we present an overview of these reactions by mechanistic paradigm. We also place this information in context of recent advances, as well as, limitations that remain for this class of reactions. 
    more » « less
  2. ; ; ; ; ; ; ; ( , Synthesis)
    Abstract

    Catalytic oxidation of tricyclic endo-norbornene-fused tetrahydrofuran with the bimetallic nanocluster Cu/Au-PVP in the presence of H2O2 or t-BuOOH as the oxidant leads to C–H bond oxidation adjacent to the ether function to give 4-oxa-tricyclo[5.2.1.0]-8,9-exo-epoxydecane, however, oxidation with Pd/Au-PVP takes place at the C=C double bond to give the same epoxide and the oxidative three-bond forming dimeric product, dodecahydro-1,4:6,9-dimethanodibenzofurano[2,3-b:7,8-b′]bisoxolane. Formation of the latter product suggests the involvement of a reactive Pd–C intermediate. Similarly, oxidative C–C bond-forming reactions are observed in cycloaddition reactions of N2-Boc-1,2,3,4-tetrahydro-γ-carbolines and 2,3-dihydroxybenzoic acid with Cu/Au-PVP (2–5 mol%) and H2O2 at 25 °C, providing two-bond-forming [4+2] cycloadducts. Under similar reaction conditions, Pd/Au-PVP did not produce the corresponding cycloadduct, indicating a need for complexation between Cu and the carboxylic acid group of 2,3-dihydroxybenzoic acid and the allylic amine function of the γ-carbolines during the cyclization reaction. The reported intermolecular coupling reactions using Pd/Au-PVP or Cu/Au-PVP nanocluster catalysts under oxidative conditions at 25 °C are unprecedented.

     
    more » « less
  3. ; ( , Catalysis Science & Technology)
    null (Ed.)
    Although palladium-catalyzed cross-coupling of aryl halides and reactive pseudohalides has revolutionized the way organic molecules are constructed today across various fields of chemistry, comparatively less progress has been made in the palladium-catalyzed cross-coupling of less reactive C–O electrophiles. This is despite the fact that the use of phenols and phenol derivatives as bench-stable cross-coupling partners has been well-recognized to bring about major advantages over aryl halides, such as natural abundance of phenols, (2) avoidance of toxic halides, (3) orthogonal cross-coupling conditions, (4) prefunctionalization of phenolic substrates by electrophilic substitution or C–H functionalization, (5) ready availability of phenols from a different pool of precursors than aryl halides. In this review, we present an overview of recent advances made in the field of palladium-catalyzed cross-coupling of C–O electrophiles with a focus on catalytic systems, (2) reaction type, and (3) class of C–O coupling partners. Although the field has been historically dominated by nickel catalysis, it is now evident that the use of more versatile, more functional group tolerant and highly active palladium catalysts supported by appropriately designed ancillary ligands enables the cross-coupling with improved substrate scope and generality, and likely represents a practical solution to the broadly applicable cross-coupling of various C–O bonds across diverse chemical disciplines. The review covers the period through June 2020. 
    more » « less
  4. ; ; ; ( , Angewandte Chemie International Edition)
    Abstract

    A palladium‐catalyzed dearomativesyn‐1,4‐oxyamination protocol using non‐activated arenes has been developed. This one‐pot procedure utilizes arenophile chemistry, and the correspondingpara‐cycloadducts are treated with oxygen nucleophiles via formal allylic substitution, providing direct access tosyn‐1,4‐oxyaminated products. The reaction conditions permit a range of arenes, as well as different O‐nucleophiles, such as oximes and benzyl alcohols. Moreover, this process was established in an asymmetric fashion, delivering products with high enantioselectivity. The dearomatized products are amenable to a multitude of further derivatizations ranging from olefin chemistry to C−H activation, giving rise to a diverse set of new functionalities. Overall, this dearomative functionalization offers rapid and controlled formation of molecular complexity, enabling straightforward access to functionalized small molecules from simple and readily available arenes.

     
    more » « less
  5. ; ; ; ( , Angewandte Chemie)
    Abstract

    A palladium‐catalyzed dearomativesyn‐1,4‐oxyamination protocol using non‐activated arenes has been developed. This one‐pot procedure utilizes arenophile chemistry, and the correspondingpara‐cycloadducts are treated with oxygen nucleophiles via formal allylic substitution, providing direct access tosyn‐1,4‐oxyaminated products. The reaction conditions permit a range of arenes, as well as different O‐nucleophiles, such as oximes and benzyl alcohols. Moreover, this process was established in an asymmetric fashion, delivering products with high enantioselectivity. The dearomatized products are amenable to a multitude of further derivatizations ranging from olefin chemistry to C−H activation, giving rise to a diverse set of new functionalities. Overall, this dearomative functionalization offers rapid and controlled formation of molecular complexity, enabling straightforward access to functionalized small molecules from simple and readily available arenes.

     
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email