The diarylation and skeletal diversification of unstrained cyclic amines was exploited to expand and modify the favorable properties of this important substrate class with pivotal roles in drug discovery. Cyclic amines were employed in the synthesis of a novel class of amino-substituted diaryliodonium salts, which were converted to highly functionalized diarylamines through an atom-efficient one-pot N-arylation/ring opening reaction with external nucleophiles. The reaction proceeds through in situ formation of a diarylammonium intermediate that undergoes a nucleophilic ring opening by cleavage of the strong C-N bond. A wide variety of diarylamines was obtained through introduction of two different aryl groups of varied electronics, and the retained iodo-substituent enables downfield diversifications of the products. More than 20 nucleophiles, including amines, phenols, carboxylic acids, thiols and halides, were alkylated with high functional group tolerance, and the strategy proved efficient also in in late-stage functionalization of natural products and pharmaceuticals.

In this work, the feasibility of triplet fusion upconversion (TFU, also named triplet-triplet annihilation upconversion) technology for the functionalization (arylation) of furans and thiophenes has been successfully proven. Activation of aryl halides by TFU leads to generation of aryl radical intermediates; trapping of the latter by the corresponding heteroarenes, which act as nucleophiles, affords the final coupling products. Advantages of this photoredox catalytic method include the use of very mild conditions (visible light, standard conditions), employment of commercially available reactants and low-loading metal-free photocatalysts, absence of any sacrificial agent (additive) in the medium and short irradiation times. The involvement of the high energetic delayed fluorescence in the reaction mechanism has been evidenced by quenching studies, whereas the two-photon nature of this photoredox arylation of furans and thiophenes has been manifested by the dependence on the energy source power. Finally, the scaling-up conditions have been gratifyingly afforded by a continuous-flow device.

A rare, structurally characterized μ1 ,η1 -hydrazonato complex is a probable intermediate in the Pd-catalyzed N-arylation of hydrazones. Starting from aryl halides the reaction proceeds efficiently and under mild conditions with chelating phosphane ligands (L2 ); even Cs2 CO3 can be used as the base [Eq. (a)]. R=alkyl, aryl, MeCO, MeO; X=Br, I.

Oxidative addition and reductive elimination are the central steps in new palladium-catalyzed chemistry that forms C-N and C-O bonds in arylamines and ethers. In the potential mechanism shown on the right the amine is formed by reductive elimination from a four-coordinate, 16-electron amido aryl complex. The use of a chelating ligand such as 1,1\'-bis(diphenylphosphanyl)ferrocene (DPPF) reduces the occurrence of the competing β-hydrogen elimination. X=Br, I; R, R\'=alkyl, aryl.

A new enantioselective palladium(II)-catalyzed benzylic C-H arylation reaction of amines is enabled by the bidentate picolinamide (PA) directing group. This reaction provides the first example of enantioselective benzylic γ-C-H arylations of alkyl amines, and proceeds with up to 97 % ee. The 2,2\'-dihydroxy-1,1\'-binaphthyl (BINOL) phosphoric acid ligand, Cs2 CO3 , and solvent-free conditions are essential for high enantioselectivity. Mechanistic studies suggest that multiple BINOL ligands are involved in the stereodetermining C-H palladation step.

Under visible-light irradiation, the gold-catalyzed intermolecular difunctionalization of alkynes with aryl diazonium salts in methanol affords a variety of α-aryl ketones in moderate to good yields. In contrast to previous reports on gold-catalyzed reactions that involve redox cycles, no external oxidants or photosensitizers are required. The reaction proceeds smoothly under mild reaction conditions and shows broad functional-group tolerance. Further applications of this method demonstrate the general applicability of the arylation of a vinyl gold intermediate instead of the commonly used protodemetalation step. This step provides facile access to functionalized products in one-pot processes. With a P,N-bidentate ligand, a stable aryl gold(III) species was obtained, which constitutes the first direct experimental evidence for the commonly postulated direct oxidative addition of an aryl diazonium salt to a pyridine phosphine gold(I) complex.

Four\'s a crowd: An efficient protocol for the formation of benzylic quaternary centers via arylation of enones using a catalyst made from Pd(O2 CCF3 )2 and 2,2\'-bipyridine is developed. For cyclic substrates, catalyst loadings as low as 1 mol % Pd are enough to afford excellent yields (>90%) using a variety of arylboronic acids. In case of acyclic substrates, the addition of KSbF6 was found to improve conversions and yields.