Controllable Enantioselective Friedel−Crafts Reaction<sup>1</sup> between Indoles and Alkylidene Malonates Catalyzed by Pseudo-<i>C</i><sub>3</sub>-Symmetric Trisoxazoline Copper(II) Complexes
Pseudo-C-3-symmetric trisoxazoline copper(II) complexes prove to be excellent catalysts in the Friedel-Crafts alkylation of indoles with alkylidene malonates. The absolute stereochemistry of this reaction is shown to be dependent on the solvent. Reactions in isobutyl alcohol afford the Friedel-Crafts alkylation adducts in excellent yields and with up to +98% ee. In 1,1,2,2-tetrachloroethane (TTCE), however, the opposite enantiomers of the products are obtained in good yields with up to -89% ee. Water tolerance of chiral catalyst trisoxazoline 2a/Cu(OTf)(2) is examined, and it is found that the addition of up to 200 equiv of water relative to catalyst in isobutyl alcohol has almost no effect on enantioselectivity but slows down the reaction. The reaction scope is studied as well. The roles of alcohol as the solvent to accelerate the reaction are discussed. The stereochemical models of asymmetric induction for reactions both in isobutyl alcohol and in TTCE are also developed.
Reactions of Optically Active Indole Mannich Bases<sup>1</sup>
作者:J. D. Albright、H. R. Snyder
DOI:10.1021/ja01518a056
日期:1959.5
Alkylidene malonates and α,β-unsaturated α′-hydroxyketones as practical substrates for vinylogous Friedel–Crafts alkylations in water catalysed by scandium(<scp>iii</scp>) triflate/SDS
作者:Jens Oelerich、Gerard Roelfes
DOI:10.1039/c4ob02487g
日期:——
Alkylidene malonates and α,β-unsaturated α′-hydroxyketones are demonstrated to be efficient classes of electrophiles for the scandium(III) triflate/sodium dodecyl sulphate (SDS) catalysed vinylogous Friedel–Crafts alkylation of indoles and pyrroles in water. These substrates contain an easily removable auxiliary group that increases affinity for the catalytic metal ion in such a way that they can compete