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

Abstract

A new chemoselective (enzymatic desymmetrization/Ru‐catalyzed C−H activation) sequence to obtain differently substituted furans from the largely available 2,5‐furandicarboxylic acid (FDCA) was developed. Series of di‐ and trisubstituted furans were prepared in very good yields and excellent chemoselectivity. This study discloses a new approach towards valorization of the furanics platform through the use of FDCA as a stable intermediate, thus circumventing the chemical instability of the parent 5‐hydroxymethylfurfural.

Catalytic C−H Functionalization of Unreactive Furan Cores in Bio‐Derived Platform Chemicals

“…An interesting example of tandem bio/metal catalysis in biomass conversion was also reported [38] . Enzymatic desymmetrization of FDCA esters by selective amidation was performed with Candida Antarctica Lipase B (CAL B) as a catalyst.…”

“… Biocatalyzed mono‐ and diamidation of FDCA esters with CAL B as a catalyst; DIPE=diisopropyl ether [38] …”

“… Ru‐catalyzed functionalization of estero‐amide derivative of FDCA with aryl boronates and vinyl‐silanes [38] …”

“…After formation of imine complex A and oxidative insertion of ruthenium into CÀ H bond in furan core, subsequent addition of RuÀ H complex B to benzylideneacetone leads to the formation of vinyloxy-ruthenium intermediate C. An interesting example of tandem bio/metal catalysis in biomass conversion was also reported. [38] Enzymatic desymmetrization of FDCA esters by selective amidation was performed with Candida Antarctica Lipase B (CAL B) as a catalyst. CAL B is a wellknown and commercially available enzyme belonging to the α/β hydrolase family.…”

“…Biocatalyzed mono-and diamidation of FDCA esters with CAL B as a catalyst; DIPE = diisopropyl ether. [38] non-decarboxylative and decarboxylative alkenylation 30-33 and 34-40, respectively, depending on the reaction conditions (Scheme 7). It should be noted that even compounds with unprotected hydroxy group can be used as a furanic substrate in the reaction, leading to compound 37 in moderate yield.…”