A photochemical C-N coupling of aryl halides with nitroarenes is demonstrated for the first time. Catalyzed by a Ni II complex in the absence of any external photosensitizer, readily available nitroarenes undergo coupling with a variety of aryl halides, providing a step-economic extension to the widely used Buchwald-Hartwig C-N coupling reaction. The method tolerates coupling partners with steric-congestion and functional groups sensitive to bases and nucleophiles. Mechanistic studies suggest that the reaction proceeds via the addition of an aryl radical, generated from a Ni I /Ni III cycle, to a nitrosoarene intermediate. Scheme 1. Methods for the formation of aryl CÀN bonds.

A gold(I)-catalyzed formal [4 + 1] cycloaddition of α-diazoesters and propargyl alcohols is disclosed, offering access to a variety of 2,5-dihydrofurans. The reaction shows a broad substrate scope and functional group tolerance. Preliminary mechanistic investigation indicates that this reaction most likely occurs through a 5-endo-dig cyclization of an α-hydroxy allene intermediate.

An efficient transition-metal-free photoinduced intracyclization of 4H-chromen-4-ones in EtOH-HO (7:1, v/v) at ambient temperature for the construction of complicated fused-ring heteroaromatics is established. The reaction proceeds smoothly without requiring any catalysts/additives.

The trichlorophenyl-, dichlorodiphenyl-, and chlorotriphenylgermanes undergo Pd-catalyzed cross-couplings with aryl bromides and iodides in the presence of tetrabutylammonium fluoride in toluene with addition of the measured amount of water. One chloride ligand on the Ge center allows efficient activation by fluoride to promote transfer of one, two or three phenyl groups from the organogermanes. The corresponding chlorophenylstannanes were found to be more reactive than chlorophenylsilanes, which in turn were more effective than chlorophenylgermanes. One chloride ligand on Ge or Si center allows efficient activation by fluoride to promote transfer of up to three aryl groups from germane or silicon. However, no haloligand was necessary to be present on Sn center, since tetraphenyltin efficiently transferred up to four phenyl groups during fluoride-promoted couplings with aryl halides. 19F NMR studies suggested formation of the fluorophenylgermanes and the hypervalent germanate species as possible intermediates.