Palladium-Catalyzed Cycloisomerization and Aerobic Oxidative Cycloisomerization of Homoallenyl Amides: A Facile and Divergent Approach to 2‑Aminofurans

A Pd-catalyzed
divergent cyclization, including cycloisomerization
and aerobic oxidative cycloisomerization of homoallenyl amides, is
described. Varieties of functionalized 2-amino-5-alkylfurans and 2-amino-5-formylfurans
can be selectively synthesized in good to excellent yields. Preliminary
mechanistic studies show that peroxide may be a key intermediate for
this Pd-catalyzed radical aerobic oxidative cycloisomerization of
homoallenyl amides. The mild reaction conditions, high atom economy,
and utilization of air as the oxygen source make this protocol very
environmentally benign and practical to the synthetic community.