3-Alkenyl-2-silyloxyindoles in vinylogous Mannich reactions: synthesis of aminated indole-based scaffolds and products.

Research paper by Beatrice B Ranieri, Andrea A Sartori, Claudio C Curti, Lucia L Battistini, Gloria G Rassu, Giorgio G Pelosi, Giovanni G Casiraghi, Franca F Zanardi

Indexed on: 18 Jan '14Published on: 18 Jan '14Published in: Organic Letters


The first Lewis acid catalyzed vinylogous Mukaiyama-type Mannich addition of 3-alkenyl-2-silyloxyindoles to in situ generated N-Boc imines has been established, which affords chiral α-alkylidene-δ-amino-2-oxindole products with good efficiency and complete γ-site- and Z-selectivity. The reaction is wide in scope, as it can be applied with equal convenience to different silyloxyindole donors and aromatic or aliphatic aminal-derived aldimine acceptors. The utility of these scaffolds is demonstrated by their easy transformation into either spirocyclopropane oxindole or homotryptamine-like products, featuring nontraditional indole-based skeleton connections.