Straight access to highly fluorescent angular indolocarbazoles via merging Au- and Mo-catalysis

Abstract

A straightforward and efficient synthesis of the two less explored types of indolocarbazoles has been developed giving rise to highly fluorescent compounds with fluorescence quantum yields around 0.7.

Mo–Catalyzed One‐Pot Synthesis of N‐Polyheterocycles from Nitroarenes and Glycols with Recycling of the Waste Reduction Byproduct. Substituent‐Tuned Photophysical Properties

“…As extended conjugated systems lead to long absorption and emission wavelengths, [45] the aryl group of 5 ab , 5 bb and 5 ac is expected to be conjugated with the molecular π‐framework. [46] Whereas the aryl‐substituted [1,2‐a]IQ ( 5 ab , 5 bb and 5 ac ) present similar Stokes shifts to reported [2,3‐b]IQ, to the best of our knowledge, ( c ‐)alkyl derivatives ( 5 al and 5 ao ) show an unprecedented well‐resolved vibrational structure and low Stokes compared to previously reported indoloquinoxalines. The highly structured short wavelength emission, with low Stokes shifts, is distinctive of relatively rigid polynuclear aromatic hydrocarbons such as anthracene (at low concentrations to prevent excimer formation).…”

“…By contrast, the aryl‐substituted 5 ab , 5 bb and 5 ac compounds exhibit red‐shifted spectra, poorly resolved vibrational structure and higher Stokes shifts (3800–4600 cm −1 , Table 6), diminishing the self‐quenching processes. As extended conjugated systems lead to long absorption and emission wavelengths, [45] the aryl group of 5 ab , 5 bb and 5 ac is expected to be conjugated with the molecular π‐framework [46] . Whereas the aryl‐substituted [1,2‐a]IQ ( 5 ab , 5 bb and 5 ac ) present similar Stokes shifts to reported [2,3‐b]IQ, to the best of our knowledge, ( c ‐)alkyl derivatives ( 5 al and 5 ao ) show an unprecedented well‐resolved vibrational structure and low Stokes compared to previously reported indoloquinoxalines.…”

Gold‐Catalyzed Reactions of 2‐Alkynyl‐1‐indolyl‐1,2‐diols with Thiols: Stereoselective Synthesis of (Z)‐α‐Indol‐3‐yl α‐(2‐Thioalkenyl) Ketones

“…1). [12] Surprisingly, the reaction of 2 a with catalytic amounts of NaAuCl 4 • 2H 2 O did not deliver any carbazole as a result of an initial attack of the indole onto the activated alkyne as expected from our previous studies. [9] Instead, the (Z)-α-indol-3-yl α-(2thioalkenyl) ketone 4 aa was afforded as a single diastereoisomer and in a high yield (Scheme 2, eq.…”

“…Modifications of the substituents at the propargylic position (R 3 ) are well tolerated (entries 1-9), and even when a methyl group was placed at this position, high yields of the desired α-indol-3-yl α-(2-thioalkenyl) ketones (4 da, db, dh) were achieved (entries 7-9). The reaction is not limited to N-protected indoles, as NHindoles have also been demonstrated to be productive, although the reaction proved to be more challenging (entries [10][11][12][13][14][15][16][17][18][19][20][24][25][26]. Despite lower yields were obtained with NH-indoles no side products were identified.…”

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

“…[28] Fernando and the team developed a new, simple and efficient methodology for the synthesis of the different angular indolocarbazole skeletons through gold-catalysed regioselective cyclization reaction and dioxomolybdenum-catalysed reductive Cadogan cyclization resulting in the two sequential carbazole formation reactions as shown in Scheme 7. [29] The salient features of this methodology are regioselectivity and high yield products. Additionally, the team investigated the photoluminescent properties of these compounds.…”