Preparation, X-ray structure and properties of a hexabrominated, symmetric indole trimer and its TCNQ adduct: a new route to functional molecular systems

Abstract

Reaction of indole with Br 2 led to isolation of an indole trimer 2, formed by linking the 2-and 3-positions of each indole to form a central aromatic ring, and brominated at the 5-and 6-positions of each indole. The Xray structure of [2]?acetone?2DMF showed p-stacking of the planar aromatic molecules with two different overlap modes with interplanar distances of 3.287 A Ê and 3.378 A Ê . Cyclic voltammetry showed one reversible oxidation for 2 and phosphorescence from frozen ethanol solution was observed. The X-ray structure of the adduct [2][TCNQ] 2 ?4DMSO was determined and showed a mixed stack arrangement where 2 alternates with two adjacent TCNQ molecules.

Study of a Convenient Method for the Preparation of Hydrosoluble Fluorescent Triazatruxene Derivatives

“…As for the reaction of indole with bromine, although in principle one equivalent of bromine would be sufficient to complete the cyclotrimerization, as a matter of fact, under these conditions, only the 2,3-dimer was isolated, whereas three equivalents were necessary to obtain the brominated symmetric indole trimers. [12] In particular, the synthesis of unsubstituted triazatruxene core 3 has been reported by isolation of hexabrominated trimer 2 and subsequent dehalogenation. [12,13] As a first synthetic approach, a mixture of 1 and Br 2 in acetonitrile was stirred overnight at room temperature.…”

“…[12] In particular, the synthesis of unsubstituted triazatruxene core 3 has been reported by isolation of hexabrominated trimer 2 and subsequent dehalogenation. [12,13] As a first synthetic approach, a mixture of 1 and Br 2 in acetonitrile was stirred overnight at room temperature. Obtained product 2 was washed and recrystallized, taking advantage of the low solubility of this intermediate compound.…”

In vitro antiproliferative/cytotoxic activity of 2,3ʹ-biindole againstvarious cancer cell lines

“…A variety of methods have been reported for the synthesis of 2 and its derivatives (Bergman, 1973;Bergman and Eklund, 1980;Bocchi and Palla, 1982, 1983, 1984Saito et al, 1982;Robertson et al, 2000;Wahlström et al, 2007;Dupeyre et al, 2011). The reaction of indole with molecular bromine yielded a pale brown solid (82%).…”

“…Facile one-step synthesis of 2 was achieved by bromination of indole (1), which underwent simultaneous dimerization (Figure 2). The preparation of the asymmetric dimer structure (2) shows a mechanism that is likely to yield 3-bromoindole (3), as 3 can react with another molecule of indole to provide coupling in a 2,3-manner (Bocchi and Palla, 1982;Robertson et al, 2000). The structure of 2 was identified by 1D and 2D NMR techniques (HETCOR, HMBC, and NOESY) and multiple-pulse NMR experiments (DEPT-90 and DEPT-135).…”

“…In 1, electrophilic substitution is preferred in position 3 with almost all reagents including halogens (Tang et al, 2007), nitrate (Gribble, 2003), sulfur (Gilow et al, 1991), Friedel-Crafts acyls (Ottoni et al, 2001), and alkyls (Zhang et al, 2012). Bromination of indole poses a dimeric product (2; Figure 1); as a result, 3-haloindoles and 2-haloindoles are unstable structures (Robertson et al, 2000;Joule and Mills, 2010;Kianmehr et al, 2012). Since the dimeric structures can react with transition metals as ligands in order to give metal complexes, they have high potential for use in catalytic processes (Omura et al, 1977;Black, 1993;Saundane et al, 2013).…”