Direct Arylation Of Arenes Research Articles

Assessing the Cooperating Ability of 6‐Hydroxypicolinic Acid and Pyridyl‐Amide Ligands in Palladium‐Mediated C−H Activation

AbstractThe behavior of 6‐hydroxypicolinic acid (pic‐6‐OH) and pyridyl‐amides as cooperating ligands in the C−H activation of arenes has been studied experimentally. When deprotonated, both compounds are chelating ligands and bear either a pyridone moiety or an N‐acyl substituent that can assist the C−H cleavage in the same way as the successful bipyridone ligands and MPAAs do. In addition, they are easily available, commercially or via straightforward syntheses. Palladium complexes of formula (NBu4)[Pd(κ2‐O, N‐pic‐6‐O)(C6F5)py] (2) and [Pd(κ2‐N, N‐ py‐CH2N(COCF3)(C6F5)py] (6) have been synthesized and their decomposition in the presence of an arene gives the C6F5‐arene coupling product, showing that the ligands enable the C−H activation of the arene (arene=pyridine, toluene, ethyl benzoate). The amount of C6F5‐arene products observed leads to the following trend in cooperating ability: pic‐6‐OH > pyridyl‐amide. DFT calculations on the pyridine activation are consistent with the experimental findings. The C−H activation does not occur for the isomeric complex (NBu4)[Pd(κ2‐O, N‐pic‐4‐O)(C6F5)py] (4) with the pyridone oxygen far from the metal, showing the involvement of this moiety in the C−H cleavage. The performance of these ligands in the direct arylation of arenes has been evaluated.

Synthesis of Polycyclic Aromatic Hydrocarbons (PAHs) via a Transient Directing Group.

In this work, an efficient synthetic route was developed to construct PAHs with diverse shape, width, and edge topology. The precursors of PAHs were obtained by using a direct arylation of arenes via a transient ligand-directed C-H functionalization strategy and the cycloaromatization was readily achieved by using a Brønsted acid catalyst. This novel route provides an opportunity to build up PAHs in a highly efficient manner.

A General Copper Catalyst for Photoredox Transformations of Organic Halides.

A broadly applicable copper catalyst for photoredox transformations of organic halides is reported. Upon visible light irradiation in the presence of catalytic amounts of [(DPEphos)(bcp)Cu]PF6 and an amine, a range of unactivated aryl and alkyl halides were shown to be smoothly activated through a rare Cu(I)/Cu(I)*/Cu(0) catalytic cycle. This complex efficiently catalyzes a series of radical processes, including reductions, cyclizations, and direct arylation of arenes.

Synthesis, structures and catalytic activity of cyclometalated rhenium complexes

Several five-membered cyclometalated rhenium complexes (1–5) were synthesized, and their photocatalytic activity on direct arylation of arenes with aryl halides was examined.

Visible-Light Photoredox in Homolytic Aromatic Substitution: Direct Arylation of Arenes with Aryl Halides

Direct arylation of unactivated arenes or heteroarenes with aryl halides could be carried out in the presence of potassium tert-butoxide and dimethyl sulfoxide under visible-light irradiation. Ir(ppy)3 was found to be an effective photoredox catalyst for this reaction. The reactions of aryl iodides occurred at room temperature. Elevated temperature was required for aryl bromides. Homolytic aromatic substitution was proposed to be the operative reaction pathway.

ChemInform Abstract: Thioethers as Directing Group for the Palladium‐Catalyzed Direct Arylation of Arenes.

Thioethers have proven to be efficient directing groups for the arylation of arenes under palladium catalysis. The thioether group can be readily removed or converted to other functional groups. Kinetic isotopic effect studies reveal that the CH cleavage of arenes might be the turnover-limiting step.

Thioethers as Directing Group for the Palladium‐Catalyzed Direct Arylation of Arenes

AbstractThioethers have proven to be efficient directing groups for the arylation of arenes under palladium catalysis. The thioether group can be readily removed or converted to other functional groups. Kinetic isotopic effect studies reveal that the CH cleavage of arenes might be the turnover‐limiting step.