Synthesis of α‐oxo‐sulfines in the indole series

Abstract

Abstract magnified image Oxindole was found to react readily with thionyl chloride to give (in an excellent yield) the isolable sulfine ( 13a ), which on heating (refluxing acetonitrile) gave isoindigo ( 15a ). The dark violet 3‐sulfinato‐oxindole ( 13a ) readily reacted with 2,3‐dimethylbutadiene to give a colorless cyclo‐adduct ( 14a ). The sulfine also reacted readily with various nucleophilic reagents, thus, thioloacetic acid gave 3‐carboxymethylthiolo‐oxindole ( 23a ). J. Heterocyclic Chem., (2010).