Iodine-Catalyzed Functionalization of Primary Aliphatic Amines to Oxazoles, 1,4-Oxazines, and Oxazinones

Unprecedented I2-catalyzed α,α-C­(sp3)-H, decarboxylative α-C­(sp3)-H, lactonized
α-C­(sp3)-H, and α,β-C­(sp3)-H
functionalized 5- and 6-annulation as well as α-C­(sp3)-H activated 6-lactonization of primary aliphatic amines are devised
under aerobic conditions. The metal-free sustainable strategy was
employed for the diverse construction of valuable five-and six-membered
polycyclic N,O-heteroaromatics such
as oxazoles, 1,4-oxazines, and oxazin-2-one with a rapid reaction
rate and high yield. The viability of this mild nonmetallic catalysis
is successfully verified through syntheses of labile chiral heterocyclic
analogues. In contrast to the common practice, this method is not
limited to use of prefunctionalized amines, directing groups (DGs)
and/or transient DGs, metal catalysts, and traditional oxidants. The
possible mechanistic pathway of the annulation reaction is investigated
by control experiments and ESI-MS data collected for a reaction mixture
of the ongoing reaction. The synthesized new compounds are potent
organic nanobuilding blocks to achieve valuable organic nanomaterials
of different sizes, shapes, and dimensions, which are under investigation
for the discovery of high-tech devices of innovative organic nanoelectronics
and photophysical properties.