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.

The synthesis of aryl amines via the formation of a C−N bond is an essential tool for the preparation of functional materials, active pharmaceutical ingredients and bioactive products. Usually, this chemical connection is only possible by transition metal‐catalyzed reactions, photochemistry or electrochemistry. Here, we report a metal‐free arene C−H amination using hydroxylamine derivatives under benign conditions. A charge transfer interaction between the aminating reagents TsONHR and the arene substrates enables the chemoselective amination of the arene, even in the presence of various functional groups. Oxygen was crucial for an effective conversion and its accelerating role for the electron transfer step was proven experimentally. In addition, this was rationalized by a theoretical study which indicated the involvement of a dioxygen‐bridged complex with a “Sandwich‐like” arrangement of the aromatic starting materials and the aminating agents at the dioxygen molecule.

Despite the widespread use of anilines, synthetic challenges to these targets still exist. Selectivity is often an issue, when using the traditional nitration-reduction sequence or more modern approaches, including arene C–H aminations catalyzed by transition metals, photosensitizers, or electrodes. Accordingly, there is still a need for general methods to rapidly, directly access specific isomers of substituted anilines. Here, we report a simple route towards the synthesis of such motifs starting from benzyl alcohols, which are converted to anilines by the use of arylsulfonyl hydroxylamines, via an aza-Hock rearrangement. Good to excellent yields are observed. The method is applicable to various benzyl alcohol surrogates (such as ethers, esters, and halides) as well as simple alkylarenes. Functionalizations of pharmaceutically relevant structures are feasible under the reaction conditions. Over ten amination reagents can be used, which facilitates the rapid assembly of a vast set of compounds.

The gold-catalyzed regioselective formation of 3-hydroxyquinoline is accessed by combining anthranils and alkynyl sulfones. The selective scission of the epoxide intermediate stems from the thermodynamic stability difference of the resultant cation according to quantum chemical calculations. The subsequent semi-pinacol rearrangement leads to the 1,2-shift of an aryl or alkyl group originating from the sulfone. A gram-scale synthesis of 3hydroxyquinoline further manifests the viability of the protocol for the preparation of this important scaffold.

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.