Cu2O/N,N′-bis(thiophen-2-ylmethyl)oxalamide is established to be an effective catalyst system for Goldberg amidation with inferior reactive (hetero)aryl chlorides, which have not been efficiently documented by Cu-catalysis to date. The reaction is well liberalized toward a variety of functionalized (hetero)aryl chlorides and a wide range of aromatic and aliphatic primary amides in good to excellent yields. Furthermore, the arylation of lactams and oxazolidinones is achieved. The present catalytic system also accomplished an intramolecular cross-coupling product.

Diaryl formation is achieved by coupling phenols and (hetero)aryl halides under the catalysis of CuI/N,N′-bis(2-phenylphenyl) oxalamide (BPPO) or CuI/N-(2-phenylphenyl)-N′-benzyl oxalamide (PPBO) at 90 °C using DMF or MeCN as the solvent. Only 0.2–2 mol % CuI and ligand are required for complete conversion, which represents the lowest catalytic loadings for a general Cu/ligand-catalyzed diaryl ether formation.

The Hoppe’s homoaldol reaction of a cyclo-hexenyl carbamate with an aldehyde followed by an unprecedented BF3·OEt2 mediated intramolecular Mukaiyama–Michael-type reaction affords the tetracyclic core structure of ent-kaurane diterpenoids. The usage of this convergent approach for assembling these natural products is demonstrated by the first asymmetric total syntheses of two highly oxidized ent-kaurane diterpenoids: Lungshengenin D and 1α,6α-diacetoxy-ent-kaura-9(11),16-dien-12,15-dione.

A class of N-(naphthalen-1-yl)-N′-alkyl oxalamides have been proven to be powerful ligands, making a coupling reaction of (hetero)aryl iodides with primary amines proceed at 50 °C with only 0.01 mol % of Cu2O and ligand as well as a coupling reaction of (hetero)aryl bromides with primary amines and ammonia at 80 °C with only 0.1 mol % of Cu2O and ligand. A wide range of coupling partners work well under these conditions, thereby providing an easy to operate method for preparing (hetero)aryl amines.

N,N′-Bis(furan-2-ylmethyl)oxalamide (BFMO), an inexpensive and conveniently available bidentate ligand, is very effective for promoting Cu-catalyzed N-arylation of anilines and cyclic secondary amines. The method enables coupling of a broad range of (hetero)aryl bromides with various (hetero)aryl amines and cyclic secondary amines at 0.5–5 mol % catalyst loadings at relatively low temperatures. For coupling with more sterically hindered acyclic secondary amines, using N,N′-bis(2,4,6-trimethoxyphenyl)oxalamide (BTMPO) as a ligand gives the better results. Additionally, high selectivity is achieved in CuI/BFMO-catalyzed direct monoarylation of piperazine with (hetero)aryl bromides to afford pharmaceutically important building blocks.

((2S,4R)-4-Hydroxy-N-(2-methylnaphthalen-1-yl)pyrrolidine-2-carboxamide (HMNPC), an amide derived from 4-hydroxy-L-proline and 2-methyl naphthalen-1-amine, is a powerful ligand for Cu-catalyzed coupling of (hetero)aryl halides with sulfinic acid salts, allowing for first time the metal-catalyzed coupling of (hetero)aryl chlorides and NaSO2Me. A considerable number of (hetero)aryl chlorides worked well, providing the pharmaceutically important (hetero)aryl methylsulfones in good to excellent yields.

AbstractAn easily prepared oxalic diamide is a powerful ligand for the copper-catalyzed coupling of aryl halides with nitrogen heterocycles. Only 1–2 mol% each of copper(I) oxide and N,N′-bis[(2-furyl)methyl]oxalamide (BFMO) are needed to form N-arylation products under mild conditions. More than 10 different types of nitrogen heterocycles are compatible with these conditions, thereby giving the corresponding N-arylation products.

The combination of Cu(acac)2 and N,N′-bis(4-hydroxyl-2,6-dimethylphenyl)oxalamide (BHMPO) provides a powerful catalytic system for hydroxylation of (hetero)aryl halides. A wide range of (hetero)aryl chlorides bearing either electron-donating or -withdrawing groups proceeded well at 130 °C, delivering the corresponding phenols and hydroxylated heteroarenes in good to excellent yields. When more reactive (hetero)aryl bromides and iodides were employed, the hydroxylation reactions completed at relatively low temperatures (80 and 60 °C, respectively) at low catalytic loadings (0.5 mol % Cu).

Indole alkaloids, one of the largest classes of alkaloids, serve as an important and rich source of pharmaceuticals and have inspired synthetic chemists to develop novel chemical transformations and synthetic strategies. Many biologically active natural products contain challenging indoline scaffolds, which feature a C3 all-carbon quaternary stereocenter that is often surrounded by a complicated polycyclic ring system. The creation of this quaternary stereocenter creates an inherent synthetic challenge because the substituents on the carbon center cause high steric repulsion. In addition, the presence of nitrogen atoms within the surrounding polycyclic rings can lead to synthetic difficulties.Oxidative coupling between two sp3-hybridized carbon anions provides a unique and powerful method for building C–C single bonds, especially for generating a C–C bond that joins one or two vicinal quaternary stereocenters. Although chemists have known of this transformation for a long time, they have only applied this reaction in total synthesis of complex natural products during the past decade. The progress of this class of reaction depends on the use of indole moieties as coupling partners.In this Account, we summarize our recent efforts to develop iodine-mediated intramolecular dearomative oxidative coupling (IDOC) reactions of indoles as part of a unified strategy for the total synthesis of three classes of indoline alkaloids. We categorized these IDOC reactions into three types based on their mode of connection to the indole moiety. In type I, the carboanion nucleophile was tethered to the indole at the C3 position. This reaction enabled the assembly of skeleton A, which features a spiro ring at the C3 position of the indole. We demonstrated the efficiency of this method by quickly assembling two classes of tetracyclic compounds and completing the total synthesis of (−)-communesins F, A, and B. For the type II IDOC reactions, the carboanion nucleophile residing at the C2 position of the indole formed a quaternary center at the C3 position of indole to produce skeleton B. We applied this IDOC reaction to synthesize two akuammiline alkaloids, vincorine and aspidophylline A. Type III IDOC reactions employed substrates with a preinstalled ring at the C2 and C3 positions of the indole. These transformations proceeded smoothly to afford polycyclic ring system C, which we used in the first enantioselective total synthesis of Kopsia alkaloid methyl N-decarbomethoxychanofruticosinate. These results further demonstrate how new chemical strategies and reactions facilitate both the first total syntheses of natural products and the discovery of more efficient synthetic routes.

A class of oxalic diamides are found to be effective ligands for promoting CuI-catalyzed aryl amination with less reactive (hetero)aryl chlorides. The reaction proceeds at 120 °C with K3PO4 as the base in DMSO to afford a wide range of (hetero)aryl amines in good to excellent yields. The bis(N-aryl) substituted oxalamides are superior ligands to N-aryl-N′-alkyl substituted or bis(N-alkyl) substituted oxalamides. Both the electronic nature and the steric property of the aromatic rings in ligands are important for their efficiency.

Copper/6-methylpicolinic acid catalyzed coupling reaction of substituted 5-bromopyrimidin-4-amines with alkynes and subsequent cyclization took place in DMSO at 100–110 °C to afford 2-chloro-pyrrolo[2,3-d]pyrimidines in moderate to excellent yields. Variable functional groups, including aromatic and aliphatic groups, could be introduced at the 6 and 7 positions using this method.

Highly asymmetric bromocyclization of tryptophol by using chiral anionic phase-transfer catalyst and DABCO-derived brominating reagent is described. Optimization of the reaction conditions revealed that the reaction rate was accelerated together with improvement of enantioselectivity by addition of catalytic DABCO-derived brominating reagent. From tryptophol, 3-bromofuroindoline could be directly obtained in excellent enantioselectivities by employing this novel methodology.

Construction of continuous all-carbon quaternary centers via intramolecular oxidative coupling was described. Intramolecular oxidative coupling of bisoxindole linked by diol derived from d-tartaric acid diastereoselectively produced C1 or C2 isomers of the annulation product. The selectivity was realized by judiciously choosing base and solvent employed in the reaction. As key intermediates for the synthesis of cyclotryptamine alkaloids, the resulting bisoxindole should be applicable to the total syntheses of complex indole alkaloids with continuous all-carbon quaternary centers.