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

Abstract

A Ru0‐catalyzed direct C‐H arylation and alkenylation of furfural imines with aryl‐ or alkenyl‐boronates, in the presence of benzylideneacetone as a sacrificial hydride acceptor, is disclosed. This reaction provides access, after hydrolysis, to C3‐arylated or vinylated furfural derivatives, and thus valorizes these relevant building‐blocks obtained from lignocellulosic biomass. This approach, involving C‐H activation by a Ru0/RuII, cycle offers several advantages, notably simple, mild and neutral reaction conditions.

Creating Diversity from Biomass: A Tandem Bio/Metal‐Catalysis towards Chemoselective Synthesis of Densely Substituted Furans

“…Recently, we reported that the temporary installation of appropriate imines as directing groups allowed the C3‐selective Ru‐catalyzed direct alkylation (Murai reaction) and arylation of furfural imines (Scheme A 2 ), as well as of OTBS‐protected (TBS= tert ‐butyldimethylsilyl) HMF imines (Scheme B) . However, the use of amides as directing groups for the C−H activation/functionalization of the HMF platform is, to our knowledge, an unknown transformation.…”

“…We started our study with the secondary amide 2 c and the tertiary amide 2 d as model compounds and adopted the same phenylation conditions as recently reported, using phenylboronic acid neopentylglycol ester (PhBnep) as the phenylating agent (Table ). No reaction occurred in presence of Ru 3 (CO) 12 at 130 °C (entries 1 and 2).…”

“…Given our previous work on the Murai reactions between imines of furfural (or HMF) and vinylsilanes, we decided to further explore whether it was possible to perform analogous insertions into our core scaffolds by using vinylsilanes as olefinic partners. Treatment of the secondary monoamide 2 a with trimethyl(vinyl)silane or triphenyl(vinyl)silane afforded the silylated products 7 a and 7 b in 53 and 76 % yield, respectively (Scheme ).…”

“…We started our study with the secondary amide 2c and the tertiaryamide 2d as model compounds and adopted the same phenylation conditions as recently reported, using phenylboronic acid neopentylglycol ester (PhBnep) as the phenylating agent [12] (Table 1). No reactiono ccurred in presence of Ru 3 (CO) 12 at 130 8C( entries 1a nd 2). The use of RuH 2 CO(PPh 3 ) 3 did not providea ny product from 2c,w hereas a1 5% yield of 4b derived from the tertiarya mide 2d was obtained (entry 3 vs. 4).…”

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

“…] in the presence of benzylidene acetone as a sacrificial hydride acceptor [70]. This arylation was performed using aryl boronates as an arylating agent in 1,4-dioxane, leading to C-H arylated furfural imines, which on subsequent acid hydrolysis gave C-3 arylated furfural (Scheme 21).…”