Synthesis of α-Ketoamides via Gold(I) Carbene Intermediates.

α-Ketoamides have been found to be an important functional group in a broad spectrum of inhibitors such as the Corona virus and other viruses. Here we report an unprecedented gold-catalyzed 2-fold reaction of a bromoalkyne with anthranils. Hydrolysis of the initial product then directly leads to α-ketoamides. Water addition to the intermediate α-iminoimidoyl halides delivered α-ketoamides from a broad range of bromoalkynes.

Metal-Free, Visible-Light-Enabled Direct C3-H Arylation of Anthranils.

An eosin Y disodium salt-catalyzed photoredox C-H arylation of anthranils is reported. A variety of aryl diazonium tetrafluoroborates were used as aryl sources, providing the C3 cross-coupled products. The in situ generated reactive radicals were trapped by anthranils, providing an alternative method to transition-metal-catalyzed C-H arylations of anthranils. Gold-catalyzed downstream transformations demonstrate the synthetic potential of these valuable building blocks.

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

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.