Ruthenium-Catalyzed Ortho C–H Arylation of Aromatic Nitriles with Arylboronates and Observation of Partial Para Arylation

Abstract

Ruthenium-catalyzed C-H arylation of aromatic nitriles with arylboronates is described. The use of RuH(CO){P(4-MeCH)} as a catalyst provided higher yields of the ortho arylation products than the conventional RuH(CO)(PPh) catalyst. The arylation takes place mostly at the ortho positions, but unprecedented para arylation was also partially observed to give ortho,para diarylation products. In addition to C-H bond cleavage, the cyano group was also found to function as a directing group for cleavage of C-O bonds in aryl ethers.

Ruthenium‐Catalyzed C‐H Arylation and Alkenylation of Furfural Imines with Boronates

“…We now describe the Ru 0 ‐catalyzed C3‐H arylation and alkenylation of furfural imines with boronate derivatives (Scheme d). The adopted protocol takes inspiration from the reported Ru 0 ‐catalyzed C‐H arylations (or alkenylations) of aryl‐ketones, amides, nitriles and imines, which make use of a sacrificial hydride scavenger to prevent the reduction of the directing group by the in situ generated Ru‐H species. Pinacolone is the most common hydride acceptor, while benzylideneacetone (BA) has been recently used for the reaction with aryl‐imines .…”

Transition-Metal-Catalyzed C–H Arylation Using Organoboron Reagents

“…Initially, they encountered an unwanted reduction reaction that accounted for equimolarly reduced aromatic ketones and investigation suggested the presence of RuH bond that reduced aromatic ketones. During a similar study [53][54][55][56][57] in 2003, researchers came across the unwanted ketone reduction issue but that remained unresolved. As resolution, they added aliphatic ketones, such as pinacolone or acetone to accept the hydride.…”

“…The Kakiuchi group communicated their seminal work on the expansion of their catalyst's utility 52 and accomplished arylation of substituted electron-deficient arenes with CN as the directing anchor (Scheme 52). 57 Despite having remarkable orthomonoarylation efficiency, minor para-arylation appeared inevitable in a few substrates that advocated the crucial impact of the electronic direction of cyanide. Replacing CN with CF3 left the protocol inefficacious for arylation, implying the paramount significance of CN presence.…”

Recent Advances in C–H Bond Functionalization with Ruthenium-Based Catalysts

“…Moreover, the reaction was best performed when using a halogenated aryl boronic acid (Scheme 32). Recently, Kakiuchi's research group successfully utilized a cyano (-CN) group as the directing group in the ruthenium-catalysed C-H bond arylation reaction [89]. They performed the arylation of aromatic nitrile with aryl boronic esters using [RuH 2 (CO)(PAr 3 ) 3 ] in the presence of KHCO 3 , resulting in aortho-arylated product along with a minor para-diarylated product (Scheme 33).…”