The intramolecular reaction of acetophenone <i>N</i>-tosylhydrazone and vinyl: Brønsted acid-promoted cationic cyclization toward polysubstituted indenes
TsNHNH2, a Brønsted acid-promoted intramolecular cyclization of o-(1-arylvinyl) acetophenone derivatives was developed, leading to polysubstituted indenes with complexity and diversity in moderate to excellent yields. In sharp contrast with either the radical or carbene involved cyclization of aldehydic N-tosylhydrazone with vinyl, a cationiccyclization pathway was involved, where N-tosylhydrazone served