Stereoselective Synthesis of Pyrroloisoindolone and Pyridoisoindolone via aza-Prins Cyclization of Endocyclic N‑Acyliminium Ions

A simple methodology has been developed for the synthesis of substituted pyrroloisoindolone and pyridoisoindolone via aza-Prins cyclization of endocyclic N-acyliminium ions, which are derived from the triflic acid treatment of regioselectively reduced N-homopropargyl imides in excellent yields. The reaction is highly diastereoselective, and only one diastereoisomer is formed during the reaction. The methodology can be utilized for the synthesis of pyrimidoisoindole.