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Visible Light-Enabled sp3 -C-H Functionalization with Chloro- and Bromoalkynes: Chemoselective Route to Vinylchlorides or Alkynes.


ABSTRACT: An unprecedented direct atom-economic chemo- and regioselective hydroalkylation of chloroalkynes and an sp3 -C-H alkynylation of bromoalkynes was achieved. The reaction partners are unfunctionalized ethers, alcohols, amides, and even non-activated hydrocarbons. We found that a household fluorescent bulb was able to excite a diaryl ketone, which then selectively abstracts a H-atom from an sp3 -C-H bond. The product of a formal alkyne insertion into the sp3 -C-H bond was obtained with chloroalkynes, providing valuable vinyl chlorides. The photo-organocatalytic hydrogen atom transfer strategy gives rise to a broad range of diversely functionalized olefins. When bromoalkynes are applied in the presence of a base, a chemoselectivity switch to an alkynylation is observed. This reaction can even be performed for the alkynylation of unactivated sp3 -C-H bonds, in this case with a preference of the more substituted carbon. Accompanying quantum chemical calculations indicate a vinyl radical intermediate with pronounced linear coordination of the carbon radical center, thus enabling the formation of both diastereoisomers after H-atom abstraction, suggesting that the (Z)-diastereoisomer is preferred, which supports the experimentally observed (E/Z)-distribution.

SUBMITTER: Adak T 

PROVIDER: S-EPMC7756539 | biostudies-literature | 2020 Dec

REPOSITORIES: biostudies-literature

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Visible Light-Enabled sp<sup>3</sup> -C-H Functionalization with Chloro- and Bromoalkynes: Chemoselective Route to Vinylchlorides or Alkynes.

Adak Tapas T   Hoffmann Marvin M   Witzel Sina S   Rudolph Matthias M   Dreuw Andreas A   Hashmi A Stephen K ASK  

Chemistry (Weinheim an der Bergstrasse, Germany) 20201015 67


An unprecedented direct atom-economic chemo- and regioselective hydroalkylation of chloroalkynes and an sp<sup>3</sup> -C-H alkynylation of bromoalkynes was achieved. The reaction partners are unfunctionalized ethers, alcohols, amides, and even non-activated hydrocarbons. We found that a household fluorescent bulb was able to excite a diaryl ketone, which then selectively abstracts a H-atom from an sp<sup>3</sup> -C-H bond. The product of a formal alkyne insertion into the sp<sup>3</sup> -C-H bo  ...[more]

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