Environmental Science and Pollution Research.
Springer Science + Business Media.
Vol. 26.
2019.
P. 559-569
A metal-free, phosphine-catalyzed intramolecular “umpolung Michael addition” on alkynes to form spiroindol(en)ines is reported. This nucleophilic catalysis enables the formation of a wide scope of five- and six-membered spiroindol(en)ines in moderate to excellent yields in batch as well as under continuous-flow conditions. Triphenylphosphine-catalyzed nucleophilic activation of alkynes allows the exclusive formation of exo-product under mild reaction conditions. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim