Direct Arylation in the Presence of Palladium Pincer Complexes

Direct arylation is an atom-economical alternative to more established procedures such as Stille, Suzuki or Negishi arylation reactions. In comparison with other palladium sources and ligands, the use of palladium pincer complexes as catalysts or pre-catalysts for direct arylation has resulted in improved efficiency, higher reaction yields, and advantageous reaction conditions. In addition to a revision of the literature concerning intra- and intermolecular direct arylation reactions performed in the presence of palladium pincer complexes, the role of these remarkably active catalysts will also be discussed.

Regioselective Ru(II)/Pd(0) Dual Catalysis: One-Pot C-H Diarylation of Five-Membered Heterocyclic Derivatives

Herein, we report a one-pot site-selective dual metal catalyzed C-H diarylation reaction for the synthesis of multiarylated thiophene and furan derivatives in yields up to 92%. The regioselectivity of the developed methodology was achieved with the sequential use of two metal catalysts within a single vessel, starting with a Ru(II)-catalyzed C3 arylation assisted by an azine directing group, followed by a Pd(0)-catalyzed C-H functionalization on the C5-position of the five-membered heterocycle. Furthermore, the kinetic studies support that the position of the nitrogen atom within the azine moiety exhibits an evident effect on the efficiency of the ruthenium-catalyzed arylation step.

Metal-Free C-C Coupling of an Allenyl Sulfone with Picolyl Amides to Access Vinyl Sulfones via Pyridine-Initiated In Situ Generation of Sulfinate Anion

Vinyl sulfones are privileged motifs known for their biological activity and synthetic utility. Synthetic transformations to efficiently access high-value compounds with these motifs are desired and sought after. Herein, a new procedure is described to form vinyl sulfone-containing compounds by selective functionalization of the C(sp³)-H bond adjacent to the pyridine ring of pharmacologically prevalent picolyl amides with an allenyl sulfone, 1-methyl-4-(propa-1,2-dien-1-ylsulfonyl)benzene. The reaction conditions are mild with no metal catalyst or additives required and display good functional group tolerance. Mechanistic studies for this unusual transformation suggest that the reaction operates via a rare pyridine-initiated and p-toluenesulfinate anion-mediated activation of the allenyl sulfone analogous to phosphine-triggered reactions.

The synthesis of imidazo[1,5-a]quinolinesviaa decarboxylative cyclization under metal-free conditions

An iodine-mediated decarboxylative cyclization was developed from α-amino acids and 2-methyl quinolines under metal-free conditions, affording a variety of imidazo[1,5-a]quinolines with moderate to good yields.

An iodine-mediated decarboxylative cyclization was developed from α-amino acids and 2-methyl quinolines under metal-free conditions, affording a variety of imidazo[1,5-a]quinolines with moderate to good yields.

Ruthenium-catalyzed direct arylations with aryl chlorides

Aryl chlorides are readily available at lower cost than the corresponding bromides and iodides, but are much more challenging as substrates in metal-catalyzed cross-couplings.

Copper-mediated C(sp3)–H amination in a multiple C–N bond-forming strategy for the synthesis of N-heterocycles

A three-component reaction for the construction of imidazo[1,5-a]pyridines through copper-promoted C(sp³)–H amination has been developed.

One-pot synthesis of 3,4,5-trisubstituted 1,2,4-triazoles via the addition of hydrazides to activated secondary amides

A general approach has been developed for the one-pot synthesis of 3,4,5-trisubstituted 1,2,4-triazoles from secondary amides and hydrazides via triflic anhydride activation followed by microwave-induced cyclodehydration. In addition, the 1,2,4-triazole moiety is shown to be a useful directing group for Ru-catalyzed C-H arylation. Access to 1,2,4-triazolophenanthridine can be achieved from the reaction products using a Pd-catalyzed intramolecular C-H functionalization reaction.