A Simple Route to Polysubstituted Indoles Exploiting Azide Induced Furan Ring Opening

Abstract

A straightforward, efficient indole synthesis based on thermolysis of 2-(2-azidobenzyl)furans with attack of the formed nitrene moiety onto the ipso position of furan ring has been developed. The cyclization is accompanied by furan ring opening and affords indoles with a 2-acylvinyl substituent suitable for further modifications.

Diversity Oriented Synthesis of Indoloazepinobenzimidazole and Benzimidazotriazolobenzodiazepine from N1‐Alkyne‐1,2‐diamines

“…General procedure for the synthesis of 2‐azido benzaldehydes derivatives (8) : Synthesis of 8 a – e were carried out according to a reported procedure by treating substituted 2‐nitrobenzaldehyde (1.0 equiv) with NaN 3 (1.5 equiv) in HMPA to give the desired products in satisfactory yields. Their spectroscopic data match those of the previously reported compounds 11b…”

Oxidative Rearrangement of 2‐(2‐Aminobenzyl)furans: Synthesis of Functionalized Indoles and Carbazoles

“…After that, the reaction mixture was concentrated in vacuo and the residue was purified by flash column chromatography (silica gel, eluent – ethyl acetate/petroleum ether=1 : 10) to afford the compound 3 . Yield: 302 mg, 95 %; pale beige solid; mp 216–217 °C (CH 2 Cl 2 /hexane=1 : 9), lit 218–219 °C; [19] 1 H NMR (400 MHz, DMSO‐ d 6 ): δ=11.80 (s, 1H), 7.60–7.40 (m, 8H), 7.31–7.28 (m, 1H), 7.11–7.07 (m, 1H), 6.89 (d, 3 J =16.1 Hz, 1H), 2.28 (s, 3H) ppm; 13 C NMR (100 MHz, DMSO‐ d 6 ): δ=197.1, 137.6, 133.5, 131.1, 130.1, 129.8 (2 C), 128.9 (2 C), 127.0, 126.7, 125.3, 124.9, 122.8, 120.3, 119.7, 111.7, 27.7 ppm.…”

“…After that, the reaction mixture was concentrated in vacuo and the residue was purified by flash column chromatography (silica gel, eluent -ethyl acetate/petroleum ether = 1 : 10) to afford the compound 3. Yield: 302 mg, 95 %; pale beige solid; mp 216-217°C (CH 2 Cl 2 /hexane = 1 : 9), lit 218-219°C; [19] 7, 125.3, 124.9, 122.8, 120.3, 119.7, 111.7, 27.7 ppm.…”

Asymmetric Synthesis of Fused Tetrahydroquinolines via Intra­molecular Aza-Diels–Alder Reaction of ortho-Quinone Methide Imines

“…The primary ortho-amino alcohols were prepared from the respective 2-aminobenzonitriles by Grignard addition 44 and successive NaBH 4 reduction of the resulting ketone. 45 The employed aldehydes were synthesized according to the literature: 2-allylbenzaldehyde 47 and hex-5-enal. 48 ortho-Hydroxybenzylation; General Procedure B 49 Following a modified procedure, a solution of BCl 3 (1.10 equiv) in CH 2 Cl 2 (1.0 M) was added carefully to a solution of the corresponding N-alkyl aniline (1.10 equiv) in DCE (0.5 M) under ice-cooling and an Ar atmosphere.…”