- Palladium-catalyzed hiyama cross-couplings of arylsilanes with 3-Iodoazetidine: Synthesis of 3-arylazetidines
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The first palladium-catalyzed Hiyama cross-coupling reactions of arylsilanes with 3-iodoazetidine were described. The protocol provides a convenient access to a variety of useful 3-arylazetidines which are of great interest in pharmaceutical laboratories in moderate to good yields (30%-88%). In addition, this strategy has the advantage of easy operation and mild reaction conditions.
- Liu, Zhenwei,Luan, Nannan,Shen, Linhua,Li, Jingya,Zou, Dapeng,Wu, Yusheng,Wu, Yangjie
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- Catalytic One-Pot Oxetane to Carbamate Conversions: Formal Synthesis of Drug Relevant Molecules
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Oxetanes are versatile building blocks in drug-related synthesis to induce property-modulating effects. Whereas related oxiranes are widely used in coupling chemistry with carbon dioxide (CO2) to afford value-added commodity chemicals, oxetane/CO2couplings remain extremely limited despite the recent advances in the synthesis of these four-membered heterocycles. Here we report an effective one-pot three-component reaction (3CR) strategy for the coupling of (substituted) oxetanes, amines and CO2to afford a variety of functionalized carbamates with excellent chemoselectivity and good yields. The process is mediated by an aluminium-based catalyst under relatively mild conditions and the developed catalytic methodology can be applied to the formal synthesis of two pharmaceutically relevant carbamates with the 3CR being a key step. (Figure presented.).
- Guo, Wusheng,Laserna, Victor,Rintjema, Jeroen,Kleij, Arjan W.
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- Merging Halogen-Atom Transfer (XAT) and Copper Catalysis for the Modular Suzuki-Miyaura-Type Cross-Coupling of Alkyl Iodides and Organoborons
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We report here a mechanistically distinct approach to achieve Suzuki-Miyaura-type cross-couplings between alkyl iodides and aryl organoborons. This process requires a copper catalyst but, in contrast with previous approaches based on palladium and nickel
- Zhang, Zhenhua,Górski, Bartosz,Leonori, Daniele
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p. 1986 - 1992
(2022/02/01)
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- A Case Study in Catalyst Generality: Simultaneous, Highly-Enantioselective Br?nsted- And Lewis-Acid Mechanisms in Hydrogen-Bond-Donor Catalyzed Oxetane Openings
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Generality in asymmetric catalysis can be manifested in dramatic and valuable ways, such as high enantioselectivity across a wide assortment of substrates in a given reaction (broad substrate scope) or as applicability of a given chiral framework across a variety of mechanistically distinct reactions (privileged catalysts). Reactions and catalysts that display such generality hold special utility, because they can be applied broadly and sometimes even predictably in new applications. Despite the great value of such systems, the factors that underlie generality are not well understood. Here, we report a detailed investigation of an asymmetric hydrogen-bond-donor catalyzed oxetane opening with TMSBr that is shown to possess unexpected mechanistic generality. Careful analysis of the role of adventitious protic impurities revealed the participation of competing pathways involving addition of either TMSBr or HBr in the enantiodetermining, ring-opening event. The optimal catalyst induces high enantioselectivity in both pathways, thereby achieving precise stereocontrol in fundamentally different mechanisms under the same conditions and with the same chiral framework. The basis for that generality is analyzed using a combination of experimental and computational methods, which indicate that proximally localized catalyst components cooperatively stabilize and precisely orient dipolar enantiodetermining transition states in both pathways. Generality across different mechanisms is rarely considered in catalyst discovery efforts, but we suggest that it may play a role in the identification of so-called privileged catalysts.
- Strassfeld, Daniel A.,Algera, Russell F.,Wickens, Zachary K.,Jacobsen, Eric N.
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supporting information
p. 9585 - 9594
(2021/07/19)
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- Highly Enantioselective, Hydrogen-Bond-Donor Catalyzed Additions to Oxetanes
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A precisely designed chiral squaramide derivative is shown to promote the highly enantioselective addition of trimethylsilyl bromide (TMSBr) to a broad variety of 3-substituted and 3,3-disubstituted oxetanes. The reaction provides direct and general access to synthetically valuable 1,3-bromohydrin building blocks from easily accessed achiral precursors. The products are readily elaborated both by nucleophilic substitution and through transition-metal-catalyzed cross-coupling reactions. The enantioselective catalytic oxetane ring opening was employed as part of a three-step, gram-scale synthesis of pretomanid, a recently approved medication for the treatment of multidrug-resistant tuberculosis. Heavy-atom kinetic isotope effect (KIE) studies are consistent with enantiodetermining delivery of bromide from the H-bond-donor (HBD) catalyst to the activated oxetane. While the nucleophilicity of the bromide ion is expected to be attenuated by association to the HBD, overall rate acceleration is achieved by enhancement of Lewis acidity of the TMSBr reagent through anion abstraction.
- Strassfeld, Daniel A.,Wickens, Zachary K.,Picazo, Elias,Jacobsen, Eric N.
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supporting information
p. 9175 - 9180
(2020/07/13)
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- Gold-Nanoparticle-Catalyzed Silaboration of Oxetanes and Unactivated Epoxides
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Supported gold nanoparticles catalyze the unprecedented insertion of a silylborane into the C-O bond of oxetanes and unactivated epoxides, forming γ- or β-silyloxy boronates in good to excellent yields. In the silaboration process the boron moiety is acting as a nucleophile and the silyl as an electrophile. No external additives or ligands are required, while the catalytic system is recyclable and reusable.
- Vasilikogiannaki, Eleni,Louka, Anastasia,Stratakis, Manolis
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p. 3895 - 3902
(2016/12/22)
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- Preparation of aryloxetanes and arylazetidines by use of an alkyl-aryl suzuki coupling
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(Chemical Equation Presented) The oxetan-3-yl and azetidin-3-yl substituents have previously been identified as privileged motifs within medicinal chemistry. An efficient approach to installing these two modules into aromatic systems, using a nickel-mediated alkyl-aryl Suzuki coupling, is presented.
- Duncton, Matthew A. J.,Estiarte, M. Angels,Tan, Darlene,Kaub, Carl,O'Mahony, Donogh J. R.,Johnson, Russell J.,Cox, Matthew,Edwards, William T.,Wan, Min,Kincaid, John,Kelly, Michael G.
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experimental part
p. 3259 - 3262
(2009/05/07)
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