Ruthenium-catalyzed coupling reaction of 2,3,5-trisubstituted furans with aryl halides through C–H bond cleavages

Ruthenium(II)-Catalyzed C–H Bond Activation and Functionalization

“…C 4 -arylation of a variety of 2,3,5-trisubstituted furans, especially those containing a formyl or an acyl group at the C 5 position, has been successfully performed with arylbromides or iodides using [RuCl 2 ( p -cymene)] 2 catalyst in the presence of only the base K 2 CO 3 (3 equiv). The reaction requires 18 h at 120 °C as no carboxylate additive has been used, but it occurs without decarboxylation of esters or formyl groups as with palladium catalysts (eq ) …”

Direct Palladium-Catalyzed C-4 Arylation of Tri-substituted Furans with Aryl Chlorides: An Efficient Access to Heteroaromatics

“…39,40 Firstly, the intermediate A was formed trough the reaction 1 with the palladium species, and a fivemember Pd cycle was generated with the help of α-carbonyl group. 41,42 Subsequently, under the abstraction of strong base, t-BuOK, on acidic hydrogen, the C-H bond was cleaved at C-4 position in furan ring and the intermediate B was produced. Lastly, reductive elimination of B gave the desired product 3 and released the Pd catalyst.…”