Intramolecular Ring Opening of Azetidines under Transition Metal-Free Conditions

Strained four-membered ring systems such as azetidines and oxetanes have been increasingly exploited as valuable synthons to generate synthetic complexity via intramolecular ring opening reactions. Herein, we report an intramolecular ring opening of azetidines under transition metal-free conditions. The described method is highly unusual, as most reports use Lewis or Brönsted acids to activate the azetidine ring. The substrates are prepared via an sp²-sp³ cross-electrophile coupling, and a one-pot approach affords high levels of molecular complexity in a single step from simple, readily available materials. Furthermore, the reaction was expanded to include the analogous oxetane substrates, revealing a hydroxymethyl handle in the cyclized product.