Intramolecular Nitrone Interrupted Click Reaction

We
document the intramolecular interception of a Cu-catalyzed azidoalkyne
cycloaddition employing a suitably placed nitrone group, providing
a simple route to the unprecedented spiro-polyheterocyclic scaffold.
The reaction is comprised of a Cu-catalyzed [3 + 2]-cycloaddition
of (2-azidoaryl)isatogen with a terminal alkyne and the intramolecular
trapping of the transient Cu-triazolide intermediate with the isatogen,
with a net formation of one C–C and two C–N bonds and
the new heterocyclic ring being spiro-annulated.