A Concise Synthesis to Benzo[c ]cinnolines via 2,2’-Dinitro-1,1’-Biphenyls Attained from a Novel Tailored Suzuki Cross-Coupling

Reductive coupling of 2,2'-dinitrobiphenyls into benzo[c]cinnolines with NaHS

An efficient and selective method for the reduction of 2,2'-dinitrobiphenyls with NaHS to prepare benzo[c]cinnoline and benzo[c]indole N-oxide was developed. This reductive coupling protocol proceeded as quick as 20 min, and gave moderate to good yields under ambient conditions. It was straightforward and easily scalable to produce various of benzo[c]cinnoline derivatives with diverse substitution patterns.

Copper-Catalyzed Aerobic Oxidative Dehydrogenative Coupling to Access Benzo[c]cinnolines

In this paper, a highly efficient copper-catalyzed oxidative dehydrogenative coupling to obtain benzo[c]cinnolines (up to 100% yield) was developed. It was found that DMAP was a highly efficient ligand for copper-catalyzed oxidation, and molecular oxygen was a green oxidizing agent. In this simple process, various functional groups were tolerated under mild reaction conditions, and the practicality of the process was demonstrated by the preparation of benzo[c]cinnolines on a gram scale and later derivatization.

Synthesis of Benzo[c]cinnolinium Salts from 2-Azobiaryls by Copper(II) or Electrochemical Oxidation

Synthesis of benzo[c]cinnolinium salts by copper(II)-promoted or electrochemical oxidation of 2-azobiaryls is described. A variety of diversely functionalized benzo[c]cinnolinium salts were easily constructed by this strategy with excellent functional group tolerance and high efficiency. An interesting fluorescence centered at 571 nm is revealed by a benzo[c]cinnolinium salt with electron push-pull substitutions. The mechanism is proposed to go through single-electron transfer driven by oxidant and intramolecular cyclization via nucleophilic addition, followed by an anion exchange.

Efficient method for the synthesis of novel methyl 4-cinnolinecarboxylate

A new method is designed for the synthesis of some novel methyl 3-aryl/alkyl-4-cinnolinecarboxylate with developed a general Richter cyclization through diazotization strategy of commercially available 2-aryl/alkyl ethynyl aniline and methyl acetate. Most substrates were achieved in moderate to excellent yields in one-pot procedures under mild reaction conditions.

Synthesis of 5,7-diarylindoles via Suzuki-Miyaura coupling in water

The synthesis of novel 5,7-diaryl and diheteroaryl indoles has been explored via efficient double Suzuki-Miyaura coupling. The method notably employs a low catalyst loading of Pd(PPh₃)₄ (1.5 mol%/coupling) and water as the reaction solvent to obtain 5,7-diarylated indoles without using N-protecting groups in up to 91% yield. The approach is also suitable for N-protected and 3-substituted indoles and constitutes an important green and convenient arylation strategy for the benzenoid ring of indoles. The synthesized diarylindoles are fluorescent.

Synthesis of Tetracyclic 2,3-Dihydro-1,3-diazepines from a Dinitrodibenzothiophene Derivative

Triply fused 1,3-diazepine derivatives have been obtained by acidic reduction of rotationally locked and sterically hindered nitro groups in the presence of an aldehyde or ketone. The nitro groups are sited on adjacent rings of a dicyanodibenzothiophene-5,5-dioxide, which also displays fully reversible two-electron-accepting behavior. The synthesis, crystallographically determined molecular structures, and aspects of the electronic properties of these new molecules are presented.