Detosylation of 3-amino-1-tosylindole-2-carbonitriles using DBU and thiophenol

Attempted detosylation of the 3-amino-1-(p-tosylamino)indole-2-carbonitriles 4a–c using either K2CO3 in EtOH or DBU in PhH at reflux gives unexpectedly the 3-(N-p-tosylamino)indole-2-carbonitriles 5a–c, respectively in high yields. Nevertheless, treatment of 1-(p-tosylamino)indoles 4a–c with thiophenol and DBU in PhH at reflux gives the detosylated 3-aminoindole-2-carbonitriles 5a–c. Reaction mechanisms supporting the tosyl migration (4→5) and the reductive detosylation (4→2) are proposed. All new compounds are fully characterised.