Manipulation of Spiroindolenine Intermediates for Enantioselective Synthesis of 3‐(Indol‐3‐yl)‐Pyrrolidines

Abstract

By manipulating the reactivity of spiroindolenine species,asequential Michael/retro-Mannich/Mannichreaction of w-indol-3-yl a,b-unsaturated ketones was developed. In the presence of 10 mol %o fac hiral phosphoric acid as the catalyst, aseries of 3-(indol-3-yl)-pyrrolidines were synthesized in high yields (up to 91 %) with excellent stereoselectivities (up to 92 %e e, > 19:1 d.r.). The products obtained here undergo diverse functional-group transformations.T he mechanistic proposal of this reaction is supported by DFT calculations. Scheme 1. Diverse reactivity of spiroindolenines. PG = protecting group.Scheme 2. Diverse reactivity of spiroindolenines. Boc = tert-butoxycarbonyl, EDG = electron-donating group.

Rhodium-Catalyzed Stereoselective Cyclization of 3-Allenylindoles and N-Allenyltryptamines to Functionalized Vinylic Spiroindolenines

“…Especially noteworthy concerning the field of intramolecular, stereoselective formation of spiroindolenines are the contributions by the You group. Using chiral phosphoramidite ligands, they developed an Ir-catalyzed asymmetric allylic substitution of indole-3-yl allylic carbonates with a broad scope. − There are also several accounts of Au-, Ag-, or Cu-catalyzed procedures using tethered terminal or internal alkynes, which lead to the aforementioned products in a stereoselective manner …”