Metal-Free and Regioselective Synthesis of Functionalized α‑Carbolines via [3 + 3] Annulation of Morita–Baylis–Hillman Acetates of Nitroalkenes with Iminoindolines

A facile, metal-free method for the
synthesis of substituted α-carbolines
from secondary Morita–Baylis–Hillman (MBH) acetates
of nitroalkenes is presented. The cascade reaction of MBH acetates
with tosyliminoindolines occurs regioselectively to form various α-carbolines
with a wide substrate scope. The reaction involves mild conditions,
and the products are formed in high yields within a short reaction
time. The amenability of the reaction to scale up and synthetic applications
of the products have been demonstrated.