Reductive Coupling

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  • enantioselective total synthesis of andrographolide and 14 hydroxy colladonin carbonyl Reductive Coupling and trans decalin formation by hydrogen transfer
    Angewandte Chemie, 2020
    Co-Authors: Lin Yang, Thomas Wurm, Binit Sharma Poudel, Michael J Krische
    Abstract:

    An enantioselective total synthesis of the labdane diterpene andrographolide, the bitter principle of the herb Andrographis paniculata (known as "King of Bitters"), was accomplished in 14 steps (LLS). Key transformations include iridium-catalyzed carbonyl Reductive Coupling to form the quaternary C4 stereocenter, diastereoselective alkene reduction to establish the trans-decalin ring, and carbonylative lactonization to install the α-alkylidene-β-hydroxy-γ-butyrolactone.

  • feedstock reagents in metal catalyzed carbonyl Reductive Coupling minimizing preactivation for efficiency in target oriented synthesis
    Angewandte Chemie, 2019
    Co-Authors: Rosalie S Doerksen, Cole C Meyer, Michael J Krische
    Abstract:

    Use of abundant feedstock pronucleophiles in catalytic carbonyl Reductive Coupling enhances efficiency in target-oriented synthesis. For such reactions, equally inexpensive reductants are desired or, ideally, corresponding hydrogen autotransfer processes may be enacted wherein alcohols serve dually as reductant and carbonyl proelectrophile. As described in this Minireview, these concepts allow reactions that traditionally require preformed organometallic reagents to be conducted catalytically in a byproduct-free manner from inexpensive π-unsaturated precursors.

  • intermolecular metal catalyzed Reductive Coupling of dienes allenes and enynes with carbonyl compounds and imines
    Chemical Reviews, 2018
    Co-Authors: Michael Holmes, Leyah A Schwartz, Michael J Krische
    Abstract:

    Metal-catalyzed Reductive Coupling has emerged as an alternative to the use of stoichiometric organometallic reagents in an increasingly diverse range of carbonyl and imine additions. In this review, the use of diene, allene, and enyne pronucleophiles in intermolecular carbonyl and imine Reductive Couplings are surveyed, along with related hydrogen autotransfer processes.

  • metal catalyzed Reductive Coupling of olefin derived nucleophiles reinventing carbonyl addition
    Science, 2016
    Co-Authors: Khoa D Nguyen, Boyoung Y Park, Tom Luong, Hiroki Sato, Victoria J Garza, Michael J Krische
    Abstract:

    BACKGROUND Since the discovery of the Grignard reaction more than a century ago, carbonyl addition mediated by premetalated reagents has played a central role in synthetic chemistry. Metal-catalyzed Reductive Coupling of π-unsaturated reactants with carbonyl compounds has emerged as an alternative to classical carbonyl addition. Although such processes bypass stoichiometric organometallic reagents and the issues of safety, selectivity, and waste associated with their use, in many cases the requisite terminal reductants are just as problematic as the organometallic reagents they replace. Catalytic Reductive Coupling via hydrogenation or transfer hydrogenation represents a more ideal strategy for carbonyl addition as relatively safe, inexpensive reductants with low molecular weights may be used (H 2 or 2-propanol). Carbonyl addition via hydrogen autotransfer is most ideal. In such processes, hydrogen embedded within a reactant alcohol mediates Reductive Coupling. By allowing alcohols to serve dually as reductant and proelectrophile (carbonyl precursor), this strategy completely bypasses the use of exogenous reductants, enabling byproduct-free carbonyl addition from the alcohol oxidation level—that is, the direct conversion of lower alcohols to higher alcohols. Alcohols are typically cheaper and more tractable than the corresponding carbonyl compounds, which is a further benefit of this approach. Ethylene (H 2 C=CH 2 ) and α-olefins are the simplest π-unsaturated reactants and are manufactured on a vast scale at production volumes exceeded only by alkanes. Hence, the discovery and development of catalytic methods that exploit olefin-derived nucleophiles in byproduct-free carbonyl Reductive Coupling represents an especially important goal of chemical research. ADVANCES Methods for the metal-catalyzed Reductive Coupling of π-unsaturated reactants with carbonyl partners have expanded considerably in recent years. A broad palette of catalysts comprising diverse metals, ligands, and terminal reductants offers access to a surprising array of transformations. In addition to providing catalytic variants of classical carbonyl additions, the mechanisms availed by transition metal catalysts have unlocked broad, new capabilities and access to hitherto unavailable volumes of chemical space. Despite these advances, intermolecular catalytic Reductive Coupling of simple linear α-olefins with unactivated carbonyl partners remains an unmet and multifaceted challenge. Beyond defining active catalysts, the use of such abundant reactants mandates an additional consideration: the identification of terminal reductants that are equally inexpensive. Additionally, to avoid waste generation (a major issue in the context of large-volume chemical manufacture), byproduct-free methods for Reductive Coupling are highly preferred. Hence, processes mediated by elemental hydrogen or hydrogen autotransfer processes that exploit hydrogen embedded in the alcohol reactant itself are especially attractive. This latter class of catalytic C–C bond–forming processes was only recently discovered. OUTLOOK The prototypical metal-catalyzed Reductive C–C bond formation and largest-volume application of homogenous catalysis is hydroformylation (>10 million metric tons/year), which transforms olefins into aldehydes through reaction with carbon monoxide and hydrogen. Despite longstanding use of this chemistry, the concept of hydrogen-mediated Reductive Coupling underlying hydroformylation lay dormant for decades. Systematic efforts to exploit hydrogenation and transfer hydrogenation in Reductive Couplings to carbonyl compounds have only begun to emerge. The impact is clear: Reactions that traditionally have used organometallic reagents may now be conducted catalytically in the absence of premetalated reagents or stoichiometric byproducts. Among the numerous possibilities for growth in this area, the development of catalytic systems for the intermolecular Reductive Coupling of ethylene and simple linear α-olefins with unactivated carbonyl partners remains an important, elusive objective. Reactions conducted from the alcohol oxidation level via hydrogen autotransfer offer a promising approach to catalytic processes of this type.

  • hydroxymethylation beyond carbonylation enantioselective iridium catalyzed Reductive Coupling of formaldehyde with allylic acetates via enantiotopic π facial discrimination
    Journal of the American Chemical Society, 2016
    Co-Authors: Victoria J Garza, Michael J Krische
    Abstract:

    Chiral iridium complexes modified by SEGPHOS catalyze the 2-propanol-mediated Reductive Coupling of branched allylic acetates 1a–1o with formaldehyde to form primary homoallylic alcohols 2a–2o with excellent control of regio- and enantioselectivity. These processes, which rely on enantiotopic π-facial discrimination of σ-allyliridium intermediates, represent the first examples of enantioselective formaldehyde C–C Coupling beyond aldol addition.

Hegui Gong - One of the best experts on this subject based on the ideXlab platform.

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Jose Luis Chiara - One of the best experts on this subject based on the ideXlab platform.

  • phthalimides as exceptionally efficient single electron transfer acceptors in Reductive Coupling reactions promoted by samarium diiodide
    Organic Letters, 2007
    Co-Authors: Tatiana Vacas, Eleuterio Alvarez, Jose Luis Chiara
    Abstract:

    Experimental and theoretical evidence shows that phthalimides are highly efficient single electron transfer acceptors in reactions promoted by samarium diiodide, affording ketyl radical anion intermediates, which participate in high-yielding inter- and intramolecular Reductive Coupling processes with different radicophiles including imides, oxime ethers, nitrones, and Michael acceptors.

  • synthesis of aminocyclitols by intramolecular Reductive Coupling of carbohydrate derived δ and e functionalized oxime ethers promoted by tributyltin hydride or samarium diiodide
    Journal of Organic Chemistry, 1997
    Co-Authors: Jose Marcocontelles, Pilar Gallego, Noureddine Khiar, Christine Destabel, Manuel Bernabé, Mercedes M Rodriguezfernandez, And Angeles Martinezgrau, Jose Luis Chiara
    Abstract:

    The intramolecular Reductive Coupling of a series of simple or polyoxygenated oxime ethers δ- or e-functionalized with bromide, α,β-unsaturated ester, aldehyde, or ketone groups is reported. The cyclization of a nitrile-tethered aldehyde is also studied. These Reductive Couplings are promoted by tributyltin hydride or samarium diiodide. The reactions proceed under mild conditions, in good chemical yield, and with high stereoselectivity. When applied to highly functionalized substrates derived from carbohydrates, this approach provides a selective entry to enantiomerically pure aminocyclitols of varying regio- and stereochemistry. In particular, the Reductive Coupling reaction of carbonyl-tethered oxime ethers promoted by samarium diiodide can be performed in a one-pot sequence, following a Swern oxidation step, allowing the direct transformation of hydroxyl-tethered oxime ethers into the corresponding aminocyclitols. Moreover, the resultant O-benzylhydroxylamine products of these cyclizations can be furth...