Bis(1-cyanovinyl acetate) Is a Linear Precursor to 3‑Oxidopyrylium Ions

Herein
we describe the first approach to 3-oxidopyrylium ions from
a linear precursor. Heating bis­(1-cyanovinyl acetate) in the presence
of a trace amount of pyridinium p-toluenesulfonate
results in a series of acyl group transfers and an intramolecular
cyclization event to form a 3-oxidopyrylium ion that can be trapped
by reaction with several dipolarophiles. When treated with dienes,
the result is a sequential [5 + 2]/[4 + 2] cycloaddition reaction
that provides sp3-rich products of high molecular complexity.