8 research outputs found

    Iridium-Catalyzed Allylic Fluorination of Trichloroacetimidates

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    A rapid allylic fluorination method utilizing trichloroacetimidates in conjunction with an iridium catalyst has been developed. The reaction is conducted at room temperature under ambient air and relies on Et<sub>3</sub>N·3HF reagent to provide branched allylic fluorides with complete regioselectivity. This high-yielding reaction can be conducted on a multigram scale and shows considerable functional group tolerance. The use of [<sup>18</sup>F]KF·Kryptofix allowed <sup>18</sup>F<sup>–</sup> incorporation in 10 min

    Iridium-Catalyzed Allylic Fluorination of Trichloroacetimidates

    No full text
    A rapid allylic fluorination method utilizing trichloroacetimidates in conjunction with an iridium catalyst has been developed. The reaction is conducted at room temperature under ambient air and relies on Et<sub>3</sub>N·3HF reagent to provide branched allylic fluorides with complete regioselectivity. This high-yielding reaction can be conducted on a multigram scale and shows considerable functional group tolerance. The use of [<sup>18</sup>F]KF·Kryptofix allowed <sup>18</sup>F<sup>–</sup> incorporation in 10 min

    Dynamic Kinetic Resolution of Allylic Azides via Asymmetric Dihydroxylation

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    The catalytic enantioselective preparation of densely functionalized amines is a fundamental synthetic challenge. To address this challenge, we report for the first time that the Winstein rearrangement can be enlisted as the racemization pathway in a dynamic kinetic resolution of allylic azides. Alkene functionalization by Sharpless dihydroxylation affords tertiary azides in excellent enantioselectivity (up to 99:1 er). This approach establishes the chirality of the tertiary azide, obviates the need to directly forge either a congested C–N or C–C bond at the new nitrogenous stereocenter, and establishes additional functionality. Several examples demonstrate further elaboration of this functionality

    Regiocontrolled Wacker Oxidation of Cinnamyl Azides

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    A highly regioselective Wacker oxidation has been developed for the oxidation of cinnamyl azides. The catalytic oxidation tolerates the azide functionality, and more than 15 β-azido ketones were isolated (25–92% yield). High regioselectivity for the aryl ketone is observed in all cases. A robustness screen was conducted to determine functional group tolerance. The products of the oxidaiton can be readily diversified

    Stereoselective Dynamic Cyclization of Allylic Azides: Synthesis of Tetralins, Chromanes, and Tetrahydroquinolines

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    This report describes the stereoselective synthesis of 3-azido-tetralins, -chromanes, and -tetrahydroquinolines via a tandem allylic azide rearrangement/Friedel–Crafts alkylation. Exposure of allylic azides with a pendant trichloroacetimidate to catalytic quantities of AgSbF<sub>6</sub> proved optimal for this transformation. This cascade successfully differentiates the equilibrating azide isomers, providing products in excellent yield and selectivity (>25 examples, up to 94% yield and >25:1 dr). In many cases, the reactive isomer is only a trace fraction of the equilibrium mixture, keenly illustrating the dynamic nature of these systems. We demonstrate the utility of this process via a synthesis of hasubanan

    Copper-Catalyzed [<sup>18</sup>F]Fluorination of (Mesityl)(aryl)iodonium Salts

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    A practical, rapid, and highly regioselective Cu-catalyzed radiofluorination of (mesityl)­(aryl)­iodonium salts is described. This protocol utilizes [<sup>18</sup>F]­KF to access <sup>18</sup>F-labeled electron-rich, -neutral, and -deficient aryl fluorides under a single set of mild conditions. This methodology is applied to the synthesis of protected versions of two important radiotracers: 4-[<sup>18</sup>F]­fluorophenylalanine and 6-[<sup>18</sup>F]­fluoroDOPA

    Evidence for a Sigmatropic and an Ionic Pathway in the Winstein Rearrangement

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    The spontaneous rearrangement of allylic azides is thought to be a sigmatropic reaction. Presented herein is a detailed investigation into the rearrangement of several allylic azides. A combination of experiments including equilibrium studies, kinetic analysis, density functional theory calculations, and selective <sup>15</sup>N-isotopic labeling are included. We conclude that the Winstein rearrangement occurs by the assumed sigmatropic pathway under most conditions. However, racemization was observed for some cyclic allylic azides. A kinetic analysis of this process is provided, which supports a previously undescribed ionic pathway

    Evidence for a Sigmatropic and an Ionic Pathway in the Winstein Rearrangement

    No full text
    The spontaneous rearrangement of allylic azides is thought to be a sigmatropic reaction. Presented herein is a detailed investigation into the rearrangement of several allylic azides. A combination of experiments including equilibrium studies, kinetic analysis, density functional theory calculations, and selective <sup>15</sup>N-isotopic labeling are included. We conclude that the Winstein rearrangement occurs by the assumed sigmatropic pathway under most conditions. However, racemization was observed for some cyclic allylic azides. A kinetic analysis of this process is provided, which supports a previously undescribed ionic pathway
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