Oxidative Conversion of Sulfonyl Indoles into 3-Alkylidene-2-oxindoles under Flow Chemical Conditions
Received: 30 July 2017
Accepted after revision: 12 September 2017
04 October 2017 (eFirst)
Sulfonyl indoles were converted into 3-alkylidene-2-oxindoles using NCS as the sole reagent under flow chemical conditions. The conjugated oxindole derivatives were generally obtained as E stereoisomers in moderate to satisfactory yields. The transformation entails the oxidation of the indole ring by NCS followed by elimination of arylsulfinic acid in order to install the exocyclic unsaturation.