Bromination of 4,6-dimethoxyindoles

Some electrophilic reactivity studies of di-(2-indolyl)dibenzofurans and di-(2-indolyl)carbazoles

“…2 This aspect of our investigations was not pursued, but reactions with hydrazine were carried out, to see if rather different macrocyclic rings could be constructed. Reaction of dialdehydes 7,9,10 and 12 all gave the corresponding bis-hydrazones 19e22 in high yield, but no dimeric macrocycle formation occurred. However, reaction of the bis-hydrazone 22 with the dialdehyde 12 afforded the 28-membered macrocyclic dimer 23 in 48% yield (Scheme 1).…”

“…Dimethyl sulfate (0.79 g, 6.28 mmol) was then added, and the mixture was stirred for a further 1 h. Water (50 mL) was added to the dark brown solution and the mixture was extracted with diethyl ether. After washing each ether extract with water (3Â30 mL), the ethereal phases were combined, dried over sodium sulfate and evaporated, giving the methylated di-indolyl dibenzofuran 2 as yellow crystals (0.82 g 64%), mp 238e240 C; IR (KBr): n max 3415,3051,2934,2104,1605,1462,1427,1338,1195,1122,1024,780,749 7,110.5,112.3,119.9,120.3,121.7,122.5,129.4 (aryl CH),124.2,127.7,127.9,138.4,141.1,155.9 (aryl C) …”

“…The dialdehyde 12 was obtained as a yellow solid (0.45 g, 80%), mp >300 C; IR (KBr): n max 3384, 1626,1451,1377,1286,1233,1152,1129,1091,810,748,664 13 C NMR (DMSO-d 6 ): d 14.6 (Me), 36.5 (CH 2 ), 110. 7,113.0,121.6,122.8,123.7,123.9,128.7 (aryl CH),113.8,122.3,123.2,127.1,137.6,141.4,163.1 (aryl C) …”

Recent Advances in Bromination of Aromatic and Heteroaromatic Compounds

“…An approach to the preparation of mono-and dibromo derivatives 83-85 of the highly active substrate 3-phenyl-4,6-dimethoxyindole was reported. 107 It required preliminary introduction of an electron-withdrawing accepting group into the indole 1-position (Scheme 67). 107 Attempts to perform the reaction with 3-phenyl-4,6-dimethoxyindole itself were unsuccessful and resulted in complicated product mixtures; that is, the reaction was uncontrolled.…”

Bromination of 2,7′-bi-indolyls and quinazolin-7-ones

“…Six novel polybrominated bi-indolyls with unique linkage and substitution patterns were isolated from the bluegreen alga Rivularia firma and four of them 1, 2, 3 and 4 are shown in Figure 1 Although brominated bi-indolyls have been found in nature, apart from a couple of methods for the synthesis of bi-indolyls with bromine atoms originally incorporated in a phenyl substituent at position 3 of the indole ring, [3][4][5][6][7] no evidence of any successful direct bromination of bi-indolyls has been reported in literature. Therefore, following previously reported work on the synthesis of 2,7′-bi-indolyls 3 and bromination of 4,6-dimethoxyindoles, 8 synthetic attempts aimed at the regioselective bromination of the 2,7′-bi-indolyl and quinazolin-7-one scaffolds using molecular bromine and N-bromosuccinimide have been undertaken delivering a library of novel mono-and polybrominated derivatives. Developing our previous research resulting in the discovery of the synthesis of macrocyclic tetraindolyls via oxidative coupling of 2,7′-bi-indolyls involving pbenzoquinone in the presence of concentrated hydrochloric acid, 3 as a part of our ongoing work, herein we report a new method for the synthesis of tetra-indolyls via acid-catalyzed coupling of brominated 2,7′-bi-indolyls and propose a mechanism for this reaction.…”