Br2 as a novel Lewis acid catalyst for Friedel–Crafts alkylation of indoles with α,β-unsaturated ketones

Mechanisms in Iodine Catalysis

“…Most likely, the triiodide anion I 3 − is formed from I 2 and I − under the reaction conditions which was additionally supported by typical UV bands at 290 and 360 nm. In turn, the reactivity of the Brønsted acid could be significantly reduced by the addition of 3 Å molecular sieve without observing a significant effect on the iodine‐catalyzed reaction . The remaining reactivity was attributed to a partial decomposition of HI to I 2 in the presence of porous materials, as the yield dropped to 0 % upon the addition of KI.…”

“…In turn, the reactivity of the Brønsted acid could be significantly reduced by the addition of 3 molecular sieve without observing as ignificant effect on the iodine-catalyzed reaction. [57] The remaining reactivity was attributedt oapartial decomposition of HI to I 2 in the presence of porousm aterials, [58] as the yield dropped to 0% upon the addition of KI. In line with previous investigations, [53a, 54a] molecular iodine turned out to be comparable if not superior to other Lewis acids like TiCl 4 ,FeCl 3 ,o rI nCl 3 under the same reactionconditions.…”

Conjugate Addition of Indoles to <i>α,β</i>-Unsaturated Ketones Using Bismuth (III) Bromide

“…Similarly, no product was formed when the same reaction was carried out in the presence of solid K 2 CO 3 . Both these results suggest that the primary role of BiBr 3 is to act as a convenient source of HBr [22]. Aqueous HBr is very corrosive and difficult to handle unlike BiBr 3 , which is an air stable and easy to handle solid.…”

An efficient synthesis of 3-diethoxyphosphoryl-4-(1H-indol-3-yl)-3,4-dihydrocoumarins: a convenient approach to 3-methylene-4-(indol-3-yl)-3,4-dihydrocoumarins

“…Among several reactions of indole, the reactions involving C-3 functionalization of indole with electron-deficient olefins have attracted and continue to attract interest from the synthetic community. While the reaction of indoles with highly electrophilic nitroolefins and enones to furnish β-(indol-3-yl) alkylated products has been widely investigated, [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] analogous reactions involving α,β-unsaturated esters to form 3-(indol-3-yl) alkanoates are rare. To date, two general strategies for the non-enantioselective synthesis of 3-(indol-3-yl) alkanoates have been reported.…”