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.