Synthesis and Optical Properties of Alkaloid Quindoline, Its Structural Analogues and Substituted δ‐Carbolines

Abstract

Alkaloid quindoline, its structural analogues and δ-carbolines were obtained through the Cadogan reaction using DPPE under solvent-free conditions as a key stage of the synthesis.Various o-nitroarylpyridines prepared by one-pot synthesis from nitroacetophenones, methyl orthoformate and acetoacetic ester enamine were used as starting materials for the preparation of δ-carbolines. 2-Aryl-3-nitro-5,6,7,8-tetrahydroquinolines obtained by reacting 2-hydroxymethylenecyclohexanone with nitroacetophenones enamines were used for the synthesis of quindoline and its structural analogs. A relationship between the structure and optical properties of the synthesized compounds was found.

A Minireview on the Scope of Cadogan Cyclization Reactions Leading to Diverse Azaheterocycles

“…Compound 91 with methoxy substitution was found to have the best quantum efficiency i. e. 0.54. However, the substitution of the benzene ring with a halogen atom resulted in a sharp decline in the quantum yield to 0.01–0.09 but showed no effect on the absorption‐emission maxima of quindoline derivatives [51] …”

“…The same group prepared δ-carbolines and quindoline along with its structural analogues through Cadogan reaction by using 1,2bis(diphenylphosphino)ethane (DPPE) as reagent as well as solvent as a key step for the synthesis. [51] For the preparation of the nitro-based substrate, various o-nitroarylpyridines 90, 93, and 95 were prepared via a one-pot synthesis from easily available three starting materials i. e. nitroacetophenones, methyl orthoformate and acetoacetic ester enamine. These substrates were further used for Cadogan cyclization as shown in Scheme 22.…”

“…However, the substitution of the benzene ring with a halogen atom resulted in a sharp decline in the quantum yield to 0.01-0.09 but showed no effect on the absorption-emission maxima of quindoline derivatives. [51] In 2021, Wenwu Liu et al designed, synthesized and investigated biological effects of harmine derivatives as potent GSK-3b (glycogen synthase kinase 3 beta)/DYRK1A (dualspecificity tyrosine phosphorylation regulated kinase 1A) dual inhibitors for the treatment of Alzheimer's disease. [52] The synthesis of desired molecules involves Cadogan cyclization reaction as shown in Scheme 23.…”

Efficient Synthesis of Pyrido[3,4-c]cinnolines and Pyrido[3,2-c]cinnolines by Intramolecular Azo Coupling Reaction of 4,6-Diaryl-3-pyridine Diazonium Salts and Study of Their Antiviral Activity

“…Monitoring of reactions and purity of the compounds obtained was by TLC on Silufol UV-254 plates, visualization under UV light. All chemicals were of analytical grade and purchased from Sigma-Aldrich Chemical Co. 2-Nitro-1-phenylethan-1-ones, 21` b c d substituted chalcones 15 , 22a–d and β-nitroenones 23a,b were synthesized according to the described procedures.…”