Palladium-Catalyzed Ortho C-H Arylation of Unprotected Anilines: Chemo- and Regioselectivity Enabled by the Cooperating Ligand [2,2'-Bipyridin]-6(1H)-one

Merging directed sp3 and nondirected sp2 C-H functionalization for Pd-catalyzed polydeuteration of (hetero)arenes

Polydeuteration has emerged as a key strategy in the development of pharmaceuticals and functional organic materials, advancing beyond monodeuteration and trideuteromethylation. We have developed methods for the polydeuteration of a wide range of organic compounds through Pd-catalyzed directed sp3 C-H activation and nondirected sp2 C-H activation, using readily available deuterium source, AcOH-d 4. This approach addresses the challenge of facilitating both directed and nondirected C-H functionalization of electronically and sterically diverse (hetero)aromatic compounds through the use of a versatile [2,2'-bipyridin]-6(1H)-one (BpyOH) ligand. This method demonstrates high functional group compatibility, readily applicable in the presence of directing functional groups such as carboxylic acids, amides, and azoles, as well as nondirecting electron-withdrawing groups such as nitro, sulfonamide, and ester groups. DFT calculations reveal that ligands influence intermediates and transition states by providing bidentate chelation, internal base, and hydrogen bonding. The Pd(BpyOH) complex exhibits well-balanced reactivity for C-H cleavage while readily forming complexes with substrates, which is relevant to other Pd-catalyzed C-H functionalization reactions. Our approach significantly broadens the scope of deuterated building blocks and late-stage deuteration, thereby facilitating evaluation of the deuterium effect in various applications across medicinal chemistry, materials science, and beyond.

Rapid access to functionalized nanographenes through a palladium-catalyzed multi-annulation sequence

Nanographenes and polycyclic aromatic hydrocarbons exhibit many intriguing physical properties and have potential applications across a range of scientific fields, including electronics, catalysis, and biomedicine. To accelerate the development of such applications, efficient and reliable methods for accessing functionalized analogs are required. Herein, we report the efficient synthesis of functionalized small nanographenes from readily available iodobiaryl and diarylacetylene derivatives via a one-pot, multi-annulation sequence catalyzed by a single palladium catalyst. This method enables the preparation of small nanographenes bearing various polar functional groups, such as hydroxy, amino, and pyridinic nitrogen atoms, which are otherwise difficult to incorporate. These functional groups provide valuable sites for further derivatization, allowing the modulation of small nanographenes' solubility, optoelectronic properties, and photochromic and vapochromic behaviors. Our new method thus provides a platform for facile access to novel carbon-based materials.

Suzuki-Miyaura cross-coupling of unprotected ortho-bromoanilines with benzyl, alkyl, aryl, alkenyl and heteroaromatic boronic esters

A Suzuki-Miyaura cross-coupling reaction was developed on unprotected ortho-bromoanilines. This operationally simple reaction was developed for the diversification of glucocorticoid receptor modulators (GRMs), showed compatibility to various boronic esters featuring unique functionalities, and was demonstrated on a gram scale.

Rhodium-Catalyzed Direct ortho-Arylation of Anilines

An efficient and broadly applicable rhodium-catalyzed direct ortho-arylation of anilines with aryl iodides relying on readily available aminophosphines as traceless directing groups is reported. Its scope and functional group compatibility were both found to be quite broad as a large variety of both aminophosphines and (hetero)aryl iodides, including complex ones, could be utilized. The ortho-arylated anilines could be obtained in high average yields, without any competing diarylation and with full regioselectivity, which constitutes a major step forward compared to other processes. The reaction is moreover not limited to aryl iodides, as an aryl bromide and a triflate could be successfully used, and could be extended to diarylation. Mechanistic studies revealed the key and unique role of the aminophosphine, acting not only as a substrate but also as a ligand for the rhodium catalyst.

C-H arylation of thiopyran derivatives with aryl halides

A C-H arylation of thiopyran derivatives with aryl halides has been developed. Under the catalysis of Pd(OAc)2/Ag2CO3, the C-H arylation takes place at the α-position of the thiopyran ring. When dibromo-substituted compounds are used as reactants, double C-H arylations may occur on the same thiopyran ring at its α- and β-positions.

Pd-catalyzed ortho-C-H arylation of free anilines with arylboric acids forming o-amino biaryls

We report a Pd-catalyzed ortho-C-H arylation of free anilines with arylboric acids. Under the reaction conditions, a wide range of arylboric acids can couple with free anilines to produce the corresponding o-amino biaryls in moderate to good yields with good functional group tolerance. This reaction can be conducted on the gram scale. The products can be easily further functionalized via transformation of the free amino group. These results indicate the potential synthetic value of this new reaction in organic synthesis.

Palladium mono-N-protected amino acid complexes: experimental validation of the ligand cooperation model in C-H activation

Mechanistic proposals for the C-H activation reaction enabled by mono-N-protected amino acid ligands (MPAAs) have been supported by DFT calculations. The direct experimental observation of the ligand-assisted C-H activation has not yet been reported due to the lack of well-defined isolated palladium complexes with MPAAs that can serve as models. In this work, palladium complexes bearing chelating MPAAs (NBu₄)[Pd(κ²-N,O-AcN-CHR-COO)(C₆F₅)py] (Ac = MeC(O); R = H, Me) and [Pd(κ²-N,O-MeNH-CH₂-COO)(C₆F₅)py] have been isolated and characterized. Their evolution in a solution containing toluene leads to the C-H activation of the arene and the formation of the C₆F₅-C₆H₄Me coupling products. This process takes place only for the ligands with an acyl protecting group, showing the cooperating role of this group in a complex with a chelating MPAA, therefore experimentally validating this working model. The carboxylate group is inefficient in this C-H activation.