Selective, Efficient and Functional Group-Tolerant CuOAc-MediatedN-Arylation of 1H-Indoles and 9H-Carbazole with Aryl Iodides Under Base-Free and Ligandless Conditions

Cu(i)-catalyzed cross-coupling of primary amines with 2,2'-dibromo-1,1'-biphenyl for the synthesis of polysubstituted carbazole

A Cu(i)-catalyzed cross-coupling of primary amines with 2,2'-dibromo-1,1'-biphenyl for the synthesis of polysubstituted carbazole has been achieved. This protocol provides an efficient strategy for the synthesis of carbazole using cheap copper catalysts with diamine ligand, and it provides convenient access to a series of carbazole derivatives in moderate yields.

Cu(i) based catalysts derived from bidentate ligands and studies on the effect of substituents for N-arylation of benzimidazoles and indoles

Four Cu(i) complexes [Cu(L^1–4)(Cl)(PPh₃)] (C1–C4) were synthesized, characterized and crystal structure of C1 was determined. Complexes were utilized as catalysts for N-arylation reaction. Probable mechanism for N-arylation reaction was proposed.

Metal-free regioselective C-3 acetoxylation of N-substituted indoles: crucial impact of nitrogen-substituent

Regioselective C-3 acetoxylation of the N-substituted indoles with PhI(OAc)₂ is described under metal-free conditions. The π-electron-deficient aryl-substituents on the N-atom of indoles remarkably favor the C-3 acetoxylation.

Enantioselective total syntheses of plectosphaeroic acids B and C

Evolution of the synthetic strategy that culminated in the first total syntheses of the structurally unique plectosphaeroic acids B (2) and C (3) is described. The successful enantioselective route to (+)-2 and (+)-3 proceeds in 6 and 11 steps from the known hexahydro-2H-pyrazinopyrrolo[2,3-b]indole-1,4-dione 39, which in turn is available in enantiomerically pure form by chemical synthesis. The central challenge in this synthesis endeavor was uniting the hexahydro-2H-pyrazinopyrrolo[2,3-b]indole-1,4-dione and cinnabarinic acid fragments of these marine alkaloids. Critical for achieving this successful C-N bond formation was the use of an iodocinnabarinic acid diester in which the amino group was masked with two Boc substituents, a Cu(I) carboxylate complex and the weak base KOAc. The highly congested C-N bond generated in this coupling, in conjunction with the delicate nature of the densely functionalized coupling partners, provided a striking testament to the power of modern copper-mediated amination methods. Two approaches, one stereoselective, for introducing the methylthio substituents of (+)-plectosphaeroic acid B were developed. The epitrisulfide ring of (+)-plectosphaeroic acid C was formed by ring expansion of an epidisulfide precursor.

Enantioselective total synthesis of plectosphaeroic acid B

The first total synthesis of a member of the plectosphaeroic acid family of fungal natural products is reported. Key steps include the late-stage formation of the hindered N6-C9" bond and stereoselective introduction of the two methylthio substituents.

Palladium-catalyzed direct and regioselective C-H bond functionalization/oxidative acetoxylation of indoles

The first general examples of palladium-catalyzed direct and selective oxidative C3-acetoxylation of indoles are presented. The mild reaction conditions (70 °C and with weak base, KOAc) in this indole C-H-acetoxylation are notable.

One-pot N-arylation of indoles directly from N-arylsulfonylindoles via consecutive deprotection and S(N)Ar Reactions with activated Aryl halides

An efficient one-pot step by step t-BuOK-mediated procedure for the synthesis of N-arylindoles has been developed in moderate to good yields. The protocol involves the consecutive deprotection of N-arylsulfonylindoles as latent indoles and subsequent S(N)Ar reactions with activated aryl halides. This tandem reaction affords an efficient and convenient preparation of N-arylindoles that benefit from prior indoles protection by arylsulfonyl group, and can shorten a reaction sequence and improve synthetic efficiency.

Efficient and Practical Synthesis of 4(5)-Aryl-1H-imidazoles and 2,4(5)-Diaryl-1H-imidazoles via Highly Selective Palladium-Catalyzed Arylation Reactions

4(5)-aryl-1H-imidazoles can be efficiently and selectively prepared by PdCl2(dppf)-catalyzed Suzuki-Miyaura reaction of commercially available 4(5)-bromo-1H-imidazole with arylboronic acids under phase-transfer conditions. On the other hand, N-unprotected 4(5)-aryl-1H-imidazoles can undergo highly selective Pd(OAc)2-catalyzed and CuI-mediated direct C-2-arylation with a variety of aryl bromides and iodides under base-free and ligandless conditions to produce 2,4(5)-diaryl-1H-imidazoles in modest to good yields. No N-arylation byproducts are observed under the experimental conditions used to prepare 2,4(5)-diaryl-1H-imidazoles.