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Sulfamate Esters Guide Selective Radical-Mediated Chlorination of Aliphatic C-H Bonds.

ABSTRACT: Masked alcohols are particularly appealing as directing groups because of the ubiquity of hydroxy groups in organic small molecules. Herein, we disclose a general strategy for aliphatic ?-C(sp3 )-H functionalization guided by a masked alcohol. Specifically, we determine that sulfamate ester derived nitrogen-centered radicals mediate 1,6-hydrogen-atom transfer (HAT) processes to guide ?-C(sp3 )-H chlorination. This reaction proceeds through a light-initiated radical chain-propagation process and is capable of installing chlorine atoms at primary, secondary, and tertiary centers.

SUBMITTER: Short MA

PROVIDER: S-EPMC5745255 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature

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Sulfamate Esters Guide Selective Radical-Mediated Chlorination of Aliphatic C-H Bonds.

Short Melanie A MA Blackburn J Miles JM Roizen Jennifer L JL

Angewandte Chemie (International ed. in English) 20171207 1

Masked alcohols are particularly appealing as directing groups because of the ubiquity of hydroxy groups in organic small molecules. Herein, we disclose a general strategy for aliphatic γ-C(sp<sup>3</sup> )-H functionalization guided by a masked alcohol. Specifically, we determine that sulfamate ester derived nitrogen-centered radicals mediate 1,6-hydrogen-atom transfer (HAT) processes to guide γ-C(sp<sup>3</sup> )-H chlorination. This reaction proceeds through a light-initiated radical chain-pr ...[more]

PMID: 29096044

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Project description:Despite the widespread success of transition-metal-catalysed cross-coupling methodologies, considerable limitations still exist in reactions at sp3-hybridized carbon atoms, with most approaches relying on prefunctionalized alkylmetal or bromide coupling partners1,2. Although the use of native functional groups (for example, carboxylic acids, alkenes and alcohols) has improved the overall efficiency of such transformations by expanding the range of potential feedstocks3-5, the direct functionalization of carbon-hydrogen (C-H) bonds-the most abundant moiety in organic molecules-represents a more ideal approach to molecular construction. In recent years, an impressive range of reactions that form C(sp3)-heteroatom bonds from strong C-H bonds has been reported6,7. Additionally, valuable technologies have been developed for the formation of carbon-carbon bonds from the corresponding C(sp3)-H bonds via substrate-directed transition-metal C-H insertion8, undirected C-H insertion by captodative rhodium carbenoid complexes9, or hydrogen atom transfer from weak, hydridic C-H bonds by electrophilic open-shell species10-14. Despite these advances, a mild and general platform for the coupling of strong, neutral C(sp3)-H bonds with aryl electrophiles has not been realized. Here we describe a protocol for the direct C(sp3) arylation of a diverse set of aliphatic, C-H bond-containing organic frameworks through the combination of light-driven, polyoxometalate-facilitated hydrogen atom transfer and nickel catalysis. This dual-catalytic manifold enables the generation of carbon-centred radicals from strong, neutral C-H bonds, which thereafter act as nucleophiles in nickel-mediated cross-coupling with aryl bromides to afford C(sp3)-C(sp2) cross-coupled products. This technology enables unprecedented, single-step access to a broad array of complex, medicinally relevant molecules directly from natural products and chemical feedstocks through functionalization at sites that are unreactive under traditional methods.

Dataset Information

Sulfamate Esters Guide Selective Radical-Mediated Chlorination of Aliphatic C-H Bonds.

Publications

Sulfamate Esters Guide Selective Radical-Mediated Chlorination of Aliphatic C-H Bonds.

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