Atmosphere-Controlled Palladium-Catalyzed Divergent Decarboxylative Cyclization of 2-Iodobiphenyls and α-Oxocarboxylic Acids

Abstract

A novel palladium-catalyzed divergent decarboxylative cyclization of 2-iodobiphenyls and α-oxocarboxylic acids utilizing the atmosphere as a controlled switch is reported. Under the protection of a nitrogen atmosphere, tribenzotropones are synthesized by a [4 + 3] decarboxylative cyclization. Employing a palladium/O2 system enables a [4 + 2] decarboxylative cyclization to assemble triphenylenes. Notably, preliminary mechanistic studies indicate that the formation of triphenylenes involves a double decarboxylation.

Regioselective synthesis of spirocyclic pyrrolines via a palladium-catalyzed Narasaka–Heck/C–H activation/[4 + 2] annulation cascade reaction

“…For the insertion of an aromatic ring, cheap and readily available 2-chlorobenzoic acid, in sharp contrast to the unselective insertion of aryne or aryl halide, inserts into palladacycle with high regioselectivity because the palladacycle reacts with 2chlorobenzoic acids through two sequential C-C crosscouplings, and two C-C bonds are formed with excellent chemoselectivity. [83][84][85][86][87][88][89][90] Consequently, we commenced our initial investigation by employing g,d-unsaturated oxime ester 1a and 2-chlorobenzoic acid 2a as the model substrates (Table 1). Fortunately, the anticipated domino reaction of 1a and 2a was conducted in the presence of Pd(OAc) 2 , P(p-Tol) 3 and K 2 CO 3 in DMF at 140 C for 12 h under an argon atmosphere, generating the desired product 3aa in 15% yield (Table 1, entry 1).…”

Research advances in palladium-catalysed intermolecular C–H annulation of aryl halides with various aromatic ring precursors

“…In 2021, our group 53 found that the transformations of α-oxocarboxylic acids as C3 or C2 insertion units could be achieved using different gas-phase atmospheres as a controlled switch (Scheme 37a). By this protocol, tribenzotropones were assembled by [4 + 3] decarboxylative cyclization under the protection of a N 2 atmosphere; [4 + 2] decarboxylative cyclization occurred to synthesize triphenylenes in the palladium/O 2 system.…”

“…Subsequently, our group and others designed various halogenated carboxylic acids as C1, C2 or C3 insertion units to construct different size-ring fused cyclic compounds via this strategy. [53][54][55][56][57][58][59][60][61][62] In these reactions, it was observed that the inser- tion of carboxylic acids usually showed good regioselectivity. Thus, the methods used o-halobenzoic acids, arynes and aryl halides as aromatic ring precursors, which could be complementary.…”

Decarbonylative/decarboxylative [4 + 2] annulation of phthalic anhydrides and cyclic iodoniums towards triphenylenes

“…13 In 2021, Yang and Liang et al reported the palladium-catalyzed divergent decarboxylative cyclization of o-iodobiphenyls and α-oxocarboxylic acids, giving triphenylenes under an oxygen atmosphere. 14 In addition to o-iodobiphenyls, cyclic diaryliodonium salts became another sought-after candidate for the construction of triphenylenes. Park and Hong et al reported the first example of directed double C-H arylation of acetanilides/benzamides with cyclic diaryliodoniums (Scheme 1a).…”

“…13 In 2021, Yang and Liang et al reported the palladium-catalyzed divergent decarboxylative cyclization of o -iodobiphenyls and α-oxocarboxylic acids, giving triphenylenes under an oxygen atmosphere. 14…”