Ag(i)/PPh3-catalyzed diastereoselective syntheses of spiro[indole-3,4′-piperidine] derivatives via cycloisomerizations of tryptamine-ynamides

A Ag(i)/PPh3-catalyzed chelation-controlled cycloisomerization of tryptamine-ynamide was developed to access the spiro[indole-3,4 '-piperidine] scaffold in a racemic and diastereoselective manner. The diastereoselective products were achieved by a chiron approach. Density functional theory (DFT) calculations indicated that strong non-covalent effects between the substrate and catalyst/ligand complex stabilized the spiroindoleninium intermediate via cation-pi-pi interactions.

Automated summary

This paper reports a chelation-controlled cycloisomerization reaction of tryptamine-ynamide catalyzed by Ag(i)/PPh3, which allows access to the spiro[indole-3,4'-piperidine] scaffold in a racemic and diastereoselective manner. Diastereoselective products are achieved through a chiron approach. Density functional theory calculations show that strong non-covalent interactions between the substrate and catalyst/ligand complex stabilize the formation of the spiroindoleninium intermediate via cation-pi-pi interactions.