Efficient approach to 1,1'-bisindoles via copper(I)-catalyzed double domino reaction

A highly efficient copper(I)-catalyzed approach for the synthesis of 1,1'-bisindoles that is based on the formation of four bonds in one step has been developed. The unprecedented three component reaction between one molecule of a 1,2-bis(2-bromoaryl)hydrazine and two molecules of a 1,3-diketone employing 10 mol% CuI as a catalyst and Cs2CO3 as a base in DMSO at 100 °C for 24 h delivers substituted 1,1'-bisindoles with yields up to 92%. The new method proceeds as a double domino condensation/Ullmann type C-C coupling. It allows an efficient and practical access to substituted 1,1'-bisindoles in one step from easily available starting materials.

Chiral Acid-Catalyzed Atroposelective Indolization Enables Access to 1,1'-Indole-Pyrroles and Bisindoles Bearing a Chiral N-N Axis

We present herein a highly atroposelective indolization for the efficient synthesis of 1,1'-biheteroaryls bearing a chiral N-N axis. Under the cooperative catalysis of chiral phosphoric acid and InBr₃, the reactions between 2,3-diketoesters and 1,3-dione-derived enamines resulted in a highly enantioselective construction of 1,1'-pyrrole-indoles with up to 92% yield, 94% enantiomeric excess (ee), or bisindoles in up to 92% ee. Derivatizations of these compounds to diverse functionalized N-N linked axially chiral biheteroaryls have also been demonstrated.

Asymmetric synthesis of N-N axially chiral compounds via organocatalytic atroposelective N-acylation

Compared with the well-developed C-C and C-N axial chirality, the asymmetric synthesis of N-N axial chirality remains elusive and challenging. Herein we report the first atroposelective N-acylation reaction of quinazolinone type benzamides with cinnamic anhydrides for the direct catalytic synthesis of optically active atropisomeric quinazolinone derivatives. This reaction features mild conditions and a broad substrate scope and produces N-N axially chiral compounds with high yields and very good enantioselectivities. Besides, the synthetic utility of the protocol was proved by a large scale reaction, transformation of the product and the utilization of the product as an acylation kinetic resolution reagent. Moreover, DFT calculations provide convincing evidence for the interpretation of stereoselection.

Formation of Complex Hydrazine Derivatives via Aza-Lossen Rearrangement

The development of a broadly applicable procedure for the aza-Lossen rearrangement is reported. This process converts amines into complex hydrazine derivatives in two steps under safe, mild conditions. This method allows the chemoselective formation of N-N bonds, resulting in the synthesis of cyclic and acyclic products while avoiding side reactions of the amphoteric (ambident) nitrogen-substituted isocyanate intermediate.

Total syntheses of (±)-spiroindimicins B and C enabled by a late-stage Schöllkopf-Magnus-Barton-Zard (SMBZ) reaction

The spiroindimicins are a family of structurally unprecedented alkaloids isolated from the deep-sea-derived marine actinomycete Streptomyces sp. SCSIO 03032. The total syntheses of (±)-spiroindimicins B and C are disclosed, the first of any member of this family. Central to the successful strategy was installing the spirocentre using a mild intramolecular Heck reaction, the assembly of a pentacyclic spirobisindole by Fischer indolization and a late-stage Schöllkopf-Magnus-Barton-Zard (SMBZ) reaction to construct the trisubstituted pyrrole.

Synthesis of Alocasin A

Herein is reported a synthesis of alocasin A (1), an alkaloid component of Alocasia macrorrhiza, a herbaceous plant used in folk medicine throughout southern Asia. A double Suzuki-Miyaura cross-coupling reaction between a 3-borylindole and 2,5-dibromopyrazine was used to assemble the heteroaromatic framework of the natural product. Removal of the protecting groups gave a synthetic sample of 1, the spectroscopic data of which matched those in the isolation report of this compound.

Total synthesis of dixiamycin B by electrochemical oxidation

N–N-linked dimeric indole alkaloids represent an unexplored class of natural products for which chemical synthesis has no practical solution. To meet this challenge, an electrochemical oxidative dimerization method was developed, which was applied as the pivotal step of the first total synthesis of dixiamycin B. This method is also general for N–N dimerization of substituted carbazoles and β-carbolines, providing entry into seldom explored chemical space.

Total synthesis of putative montamine and a proposed structural reassignment

The spectroscopic data for synthetic montamine does not match the proposed N,N′-linked structure and closely resembles a known 4,4′-bismoschamine natural product.