Recent Advancements in Transition‐Metal‐Catalyzed One‐Pot Twofold Unsymmetrical Difunctionalization of Arenes

Abstract

Transition‐metal‐catalyzed direct C−H bond activation reactions have been embraced as a powerful synthetic tool to access diverse functionalized arenes. However, site‐selective incorporation of multiple distinct functionalities in an arene has always been a formidable challenge. Recent efforts from the synthetic community have disclosed a few dynamic synthetic approaches to fabricate multifunctionalized arenes in one‐pot using a single catalytic system. These reports manifested the immense potential of such approaches to expedite contemporary organic synthesis towards building molecular complexity. In this minireview, we have illustrated the recent progress in this area, highlighting the contribution from several synthetic chemists including our group.

Ruthenium-catalyzed C–H bond functionalization in cascade and one-pot transformations

“…The mechanistic aspects [28] and catalytic cycles, which have been previously presented in articles and reviews on ruthenium-catalyzed C-H bond functionalizations [29][30][31][32][33][34][35][36][37][38][39][40][41], are not described in detail, but quoted when necessary for the understanding of the sequence. Bis-functionalization reactions represented by ortho, ortho'-C-C bond formation such as double arylation or double alkenylation for instance, are not considered since the same catalytic cycle operates twice [42]. Examples including the formation/cleavage of multiple bonds via annulation [43][44], carbonylation [45][46][47][48], decarboxylation [49][50][51] or other multicomponent reactions [52] operating with a single ruthenium catalytic cycle are also not discussed herein.…”

Sequential Catalytic Functionalization of Aryltriazenyl Aldehydes for the Synthesis of Complex Benzenes

“…In addition, it would be beneficial if the coordinating group was able to promote, not only one, but multiple C–H functionalization reactions in a selective way. 4 , 5 …”

“…The synthetic utility of this approach would be significantly improved if the distinct C–H bonds could be selectively functionalized using different coupling partners. 4 To achieve these aims, we selected aryl aldehydes substituted with 2-triazenyl groups ( Scheme 1 c). 23 The triazene group offers many potential advantages: (1) although not previously reported, the triazene group should be capable of acting as a chelating group for metal-catalyzed intermolecular hydroacylation, with the first nitrogen atom positioned to form a stable five-membered acyl-metal-hydride complex; 7d (2) catalyst coordination to the second nitrogen atom would direct the metal center to the ortho –C–H bond; 24 (3) the electron-donating properties of the triazene would promote electrophilic aromatic substitution reactions; (4) triazene groups can be easily removed; 25 and (5) triazenes can be transformed to a wide range of alternative functional groups.…”

Copper/Palladium Bimetallic System for the Synthesis of Isobenzofuranones through [4 + 1] Annulation between Propiophenones and Benzoic Acids

“…To finish the annulation, we did believe that the activation of a C–H bond on the ortho carbon atom of a carboxylic acid or amide was a key step to start the transformation. In general, the carboxyl group can be seen as a directing group to direct metal catalysts to functionalize a C–H bond on its ortho position . Now that we have already finished the desaturation of ketones, we may bring another transition-metal salt, such as Pd, Rh, or Ir, into this reaction to realize the combination of benzoic acids and in situ generated enones.…”