Metalation

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Victor Snieckus - One of the best experts on this subject based on the ideXlab platform.

Paul Knochel - One of the best experts on this subject based on the ideXlab platform.

  • preparation of functionalized aryl heteroaryl and benzylic potassium organometallics using potassium diisopropylamide in continuous flow
    Angewandte Chemie, 2020
    Co-Authors: Johannes H Harenberg, Niels Weidmann, Paul Knochel
    Abstract:

    We report the preparation of lithium-salt-free KDA (potassium diisopropylamide; 0.6 m in hexane) complexed with TMEDA (N,N,N',N'-tetramethylethylenediamine) and its use for the flow-Metalation of (hetero)arenes between -78 °C and 25 °C with reaction times between 0.2 s and 24 s and a combined flow rate of 10 mL min-1 using a commercial flow setup. The resulting potassium organometallics react instantaneously with various electrophiles, such as ketones, aldehydes, alkyl and allylic halides, disulfides, Weinreb amides, and Me3 SiCl, affording functionalized (hetero)arenes in high yields. This flow procedure is successfully extended to the lateral Metalation of methyl-substituted arenes and heteroaromatics, resulting in the formation of various benzylic potassium organometallics. A Metalation scale-up was possible without further optimization.

  • regioselective c h activation of substituted pyridines and other azines using mg and zn tmp bases
    SynOpen, 2018
    Co-Authors: Moritz Balkenhohl, Paul Knochel
    Abstract:

    The Metalation of substituted pyridines, diazines and related N -heterocycles using TMPMgCl·LiCl, TMP 2 Mg·2LiCl, TMPZnCl·LiCl or TMP 2 Zn·2LiCl 2 ·2MgCl 2 (TMP = 2,2,6,6-tetramethylpiperidyl) in the presence or absence of a Lewis acid is reviewed. Contents 1 Introduction 2 Magnesiation of Pyridines and Related Azines 2.1 Magnesiations using TMPMgCl·LiCl 2.2 Magnesiations using TMP 2 Mg·2LiCl and Related Bases 2.3 BF 3 ·OEt 2 Promoted Metalations of Pyridines 3 Zincation of Pyridines and Related Azines using TMPZnCl·LiCl and TMP 2 Zn·2LiCl·2MgCl 2 4 Metalation of Pyridines using other TMP-Bases 5 Magnesiation and Zincation of Diazines 6 Conclusion

  • selective lithiation magnesiation and zincation of unsymmetrical azobenzenes using continuous flow
    Organic Letters, 2017
    Co-Authors: Marthe Ketels, Konstantin Karaghiosoff, David B Konrad, Dirk Trauner, Paul Knochel
    Abstract:

    A mild and general set of Metalation procedures for the functionalization of unsymmetrical azobenzenes using a commercially available continuous-flow setup is reported. The Metalations proceed with TMPLi under convenient conditions (0 °C, 20 s), and various classes of electrophiles can be used. With sensitive substrates, an in situ trapping Metalation in which TMPLi is added to a mixture of the azobenzene and ZnCl2 or MgCl2·LiCl was very effective for achieving high yields.

  • lewis acid triggered regioselective magnesiation and zincation of uracils uridines and cytidines
    Organic Letters, 2016
    Co-Authors: Lydia Klier, Eider Aranzamendi, Dorothee Ziegler, Konstantin Karaghiosoff, Thomas Carell, Johannes Nickel, Paul Knochel
    Abstract:

    The Lewis acid MgCl2 allows control of the Metalation regioselectivity of uracils and uridines. In the absence of the Lewis acid, Metalation of uracil and uridine derivatives with TMPMgCl·LiCl occurs at the position C(5). In the presence of MgCl2, zincation using TMP2Zn·2LiCl·2MgCl2 occurs at the position C(6). This Metalation method provides easy access to functionalized uracils and uridines. Using TMP2Zn·2LiCl·2MgCl2 also allows to functionalize cytidine derivatives at the position C(6).

  • continuous flow magnesiation or zincation of acrylonitriles acrylates and nitroolefins application to the synthesis of butenolides
    Organic Letters, 2016
    Co-Authors: Maximilian A Ganiek, Marthe Ketels, Matthias R Becker, Paul Knochel
    Abstract:

    Scalable continuous flow procedures are reported for the Metalation and downstream functionalization of β-substituted acrylates. The flow conditions allow the Metalation of acrylonitriles, acrylates, and nitroolefins at 0.25–2.50 mmol/min conversion rates. Magnesiations can be performed with short residence times (1–20 min) and near-ambient temperature using TMPMgCl·LiCl. Further, high temperature zincation (≤90 °C) using TMPZnCl·LiCl is possible. This method allows a simple entry to 2(5H)-furanones by flow generation of magnesiated acrylates and a subsequent reaction with aldehydes.

Kare B Jorgensen - One of the best experts on this subject based on the ideXlab platform.

  • directed ortho Metalation and anionic ortho fries rearrangement of polycyclic aromatic o carbamates regioselective synthesis of substituted chrysenes
    Journal of Organic Chemistry, 2018
    Co-Authors: Sindhu Kancherla, Victor Snieckus, Marianne Lorentzen, Kare B Jorgensen
    Abstract:

    A general method for the regioselective synthesis of a series of ortho-substituted chrysenyl N,N-diethyl-O-carbamates by the directed ortho-Metalation (DoM) strategy is reported. The starting O-carbamates were prepared from the corresponding chrysenols, available by oxidative photochemical cyclization or directed remote Metalation tactics. Chrysen-1-yl and chrysene-3-yl ring site selectivity of directed ortho-Metalation (DoM) and anionic ortho-Fries rearrangement (AoF) protocols, with s-BuLi/TMEDA, followed by electrophilic quench using a selection of electrophiles, were observed, leading to new chrysenyl derivatives. 5-Chrysenyl N,N-diethyl-O-carbamate underwent instant AoF rearrangement even at −100 °C to furnish chrysenyl o-hydroxycarboxamide. Iterative DoM reactions were carried out to gain insight into the regioselectivity factors.

  • Directed ortho-Metalation and Anionic ortho-Fries Rearrangement of Polycyclic Aromatic O‑Carbamates: Regioselective Synthesis of Substituted Chrysenes
    2018
    Co-Authors: Sindhu Kancherla, Victor Snieckus, Marianne Lorentzen, Kare B Jorgensen
    Abstract:

    A general method for the regioselective synthesis of a series of ortho-substituted chrysenyl N,N-diethyl-O-carbamates by the directed ortho-Metalation (DoM) strategy is reported. The starting O-carbamates were prepared from the corresponding chrysenols, available by oxidative photochemical cyclization or directed remote Metalation tactics. Chrysen-1-yl and chrysene-3-yl ring site selectivity of directed ortho-Metalation (DoM) and anionic ortho-Fries rearrangement (AoF) protocols, with s-BuLi/TMEDA, followed by electrophilic quench using a selection of electrophiles, were observed, leading to new chrysenyl derivatives. 5-Chrysenyl N,N-diethyl-O-carbamate underwent instant AoF rearrangement even at −100 °C to furnish chrysenyl o-hydroxycarboxamide. Iterative DoM reactions were carried out to gain insight into the regioselectivity factors

  • directed Metalation suzuki miyaura cross coupling strategies regioselective synthesis of hydroxylated 1 methyl phenanthrenes
    Journal of Organic Chemistry, 2015
    Co-Authors: Kare B Jorgensen, Toni Rantanen, Thilo Dorfler, Victor Snieckus
    Abstract:

    A general, efficient, and regioselective synthesis of a series of hydroxylated 1-methylphenanthrenes 9 by a combined directed ortho Metalation (DoM)–Suzuki–Miyaura cross-coupling–directed remote Metalation (DreM) sequence is reported. Diversity to this methodology was achieved by a regioselective DoM rather than DreM reaction, affording more highly substituted phenanthrols (Table 2). Application of the turbo-Grignard reagent (i-PrMgCl·LiCl) in the Ni-catalyzed Corriu–Kumada reaction gave efficient decarbamoylation (Tables 3 and 4). Additional features are the TMS protecting group and halo-induced ipso-desilylation tactics applied to the regioselective synthesis of phenanthrenes (Scheme 2).

Toni Rantanen - One of the best experts on this subject based on the ideXlab platform.

Katherine Groom - One of the best experts on this subject based on the ideXlab platform.