Photoassisted Diversity-Oriented Synthesis: Accessing 2,6-Epoxyazocane (Oxamorphan) Cores

The
modular synthesis of photoprecursors and their photoinduced cyclization
into substituted 1-benzazocanes of two distinct topologies is described.
The key step producing an extended polyheterocyclic system involves
the photogeneration of azaxylylenes and their subsequent intramolecular
cycloaddition with furan-containing pendants tethered either via the
aniline nitrogen or through the carbonyl group containing arm. The
primary photoproductssecondary or tertiary anilines which
are not acylated at the nitrogen atomundergo facile acid-catalyzed
or spontaneous ring-opening–ring-closing rearrangement to yield
fused polyheterocyclic structures possessing a 2,6-epoxyazocane (or
oxamorphan) core.