Palladium‐Catalyzed Oxidative Double CH Functionalization/Carbonylation for the Synthesis of Xanthones

Abstract

Zwei auf einmal: Xanthone mit verschiedenen funktionellen Gruppen wurden mit CO (Ballon) in Gegenwart eines einfachen Katalysatorsystems bestehend aus Pd(OAc)2, K2S2O8 und Trifluoressigsäure erhalten (siehe Schema). Erste mechanistische Studien legen nahe, dass die zweite C‐H‐Funktionalisierung geschwindigkeitsbestimmend ist.

Uses of K2S2O8 in Metal-Catalyzed and Metal-Free Oxidative Transformations

“…74b Similar to pyridocarbonylation, a palladium-catalyzed double C−H activation/carbonylation of diarylethers with CO gas was developed by Lei and co-workers, using K 2 S 2 O 8 as a terminal oxidant. 75 Although this reaction could be performed with other oxidants such as MnO 2 or BQ, the author used K 2 S 2 O 8 in the subsequent screening to prepare various xanthones. All these carbonylation reactions with Pd(II)/K 2 S 2 O 8 proceeded with the Pd(II)/Pd(0) catalytic cycle.…”

Palladium-Catalyzed Carbonylative Homocoupling of 2-Iodophenols for the Synthesis of Symmetrical Xanthones

“…11 With regard to carbonylation protocols, Lei and co-workers reported the Pd-catalyzed double C–H activation and carbonylation strategy for xanthones synthesis starting from diaryl ethers (Scheme 1e ). 12 The catalytic system Pd(OAc) 2 /K 2 S 2 O 8 and TFA were used in the presence of a CO atmosphere for this transformation.…”

Palladium(II)‐Catalyzed Tandem Synthesis of Acenes Using Carboxylic Acids as Traceless Directing Groups

“…[11,12] We were intrigued by the possibility of atandem transformation employing removable carboxylic acid directing groups,which simultaneously afforded catalytic control and efficiency.I np articular,w es peculated that the olefinated intermediate generated in situ as ar esult of the Pd(II)-catalyzed, carboxyl-directed alkenylation of ad iaryl carboxylic acid, could be further utilized for another C-H activation in the context of the same directing group.T he sequential C-H functionalization approach is ah ighly efficient method for intramolecular cyclization of diaryl compounds. [13] Subsequently,wehypothesized that rollover of the palladated intermediate might enable coordination to an alkene moiety, [14] which would set the stage for intramolecular C À Cbond formation. Finally,the carboxylate group could be removed in atraceless fashion by decarboxylative aromatization, affording the desired anthracene products.Ifsuccessful, this strategy represents an ovel approach to step-economical synthesis of diversely functionalized anthracene and heteroacene derivatives (Scheme 1).…”