Visible‐Light‐Induced Aerobic Intramolecular Cyclization of (2‐Aminophenyl)(1H‐indol‐1‐yl)methanones: Direct Access to Bioactive Tryptanthrin and its Derivatives

Abstract

Visible-light-induced mild, transition metal, base, and photocatalyst-free green protocol has been developed for the synthesis of tryptanthrin and its derivatives. The present reaction is compatible with a wide range of substrates with good to high yields. Further, a novel synthetic transformation of tryptanthrin derivatives has been achieved by the decarboxylative addition of cyanoacetic acid for the first time. This reaction proceeds by visible-light-induced single electron transfer between the substrate and oxygen, followed by intramolecular cyclization without the use of an external photocatalyst.

Synthesis, structure-activity relationship and evaluation of antifungal activity of tryptanthrin derivatives against drug-resistant Candida albicans

“…(dd, J = 7.9, 0.9 Hz, 1H), 8.03 (t, J = 5.5 Hz, 2H), 7.88 (m, 2H), 7.69 (t, J = 7.6 Hz, 1H). Consistent with the reference[23].8-chloro-indolo [2,1-b ] quinazolin-6,12-dione (3c) 8-nitro-indolo [2,1-b] quinazolin-6,12-dione (3f) As a yellow solid; yield: 45%; m.p. 234.3-237.3 ℃; 1 H NMR (600 MHz, DMSO) δ 8.73 (dd, J = 8.8, 2.1 Hz, 1H), 8.69 (d, J = 8.8 Hz, 1H), 8.56 (d, J = 2.0 Hz, 1H), 8.37 (d, J = 7.8 Hz, 1H), 8.00 (d, J = 3.7 Hz, 2H), 7.79 (dt, J = 8.1, 4.1 Hz, 1H).…”

I2‐Promoted sp3 C−H Oxidation/Annulation Sequences for the Synthesis of Indoloquinolines from 2‐(1H‐indol‐2‐yl)anilines and Aryl Methyl Ketones

“…The oximes 4 a-b were synthesized in excellent yields of 92-94% by the condensation of hydroxylamine with 3 c and 3 k respectively. [13] Reduction of product 3 c by NaBH 4 delivered the corresponding alcohol 5 in 90% yield. [14b] In addition, the thiomethyl group of compound 3 f was oxidized [14] into sulphoxide 6 and sulfone 7 by 2 and 4 equivalents of m-CPBA as shown in Scheme 2.…”

“…were added. was monitored by 13 C{ 1 H} NMR, and results are provided in the supporting information (Figure 2).…”

“…Further, a series of synthetic transformations were also carried out. The oximes 4 a – b were synthesized in excellent yields of 92–94% by the condensation of hydroxylamine with 3 c and 3 k respectively [13] …”

Sustainable Synthesis through Catalyst‐Free Photoinduced Cascaded Bond Formation

“…[10a-c] In 2023, Rajeshkumar and co-workers reported a cascade CÀ N and CÀ O bond formation through intramolecular cyclization of (2-aminophenyl)(1H-indol-1-yl)methanones 28 a under blue LED irradiation to synthesize bioactive tryptanthrin derivatives 28 b (Scheme 28). [60] Previously this transformation was achieved by Albrecht and co-workers using Cu catalyst. [61] Conversely, without even using any catalyst or additive this mild strategy displayed broad functional group tolerance while providing good yield of tryptanthrin product.…”