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.

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.

b-(2-Alkynylphenyl)-a,b-ynones undergo a gold-catalyzed oxidative two-fold cyclization in the presence of N-oxides to give 1,3-disubstituted-8H-indeno[1,2-c]furan-8-ones in good yields. This cascade process is triggered by a selective oxygen transfer from an N-oxide onto the gold-activated alkynone to generate a a-dioxocarbene intermediate which, via carbene transfer across the remaining alkyne moiety and subsequent cyclization through nucleophilic attack by a carbonyl oxygen, achieves the construction of 1,3disubstituted fused polycyclic furans.

A highly chemo‐ and stereoselective addition of unprotected phenols to haloalkynes was developed. A ligand and counterion controlled process enabled the highly site‐selective and chemoselective C‐H bond functionalization of phenol derivatives with haloalkynes in moderate to excellent yield at room temperature. The simple availability of the starting materials in combination with the preferred para‐C‐H functionalization over a competing O‐H insertion makes this an attractive protocol. The stereoselectivity of the products depends on the choice of the catalyst. From a synthetic prospective, this method offers an efficient route towards vinyl chlorides, which are valuable precursors for the synthesis of pharmaceutical drugs.

A highly efficient gold-catalyzed cycloisomerization of 1,5-diynes was developed. Various functional groups are tolerated under the mild reaction conditions, which provides an alternative approach for the synthesis of indeno­[1,2-c]­furans. On the basis of mechanistic studies, including crossover experiments, deuterium labeling, and computational chemistry, the product formation proceeds via a formal [5,5]-sigmatropic rearrangement, a yet unknown reactivity pattern in gold catalysis. Instead of a synchronous concerted [5,5]-sigmatropic rearrangement and beyond an asynchronous concerted mode, each involving a single transition state, two energetically low transition states (1.8 and 5.6 kJ/mol) and an intermediate associate of the migrating benzyl cation and the vinyl gold species could be located in the computations.