Trapping Reactions of Benzynes Initiated by Intramolecular Nucleophilic Addition of a Carbonyl Oxygen to the Electrophilic Aryne

We
describe here reactions in which a carbonyl oxygen atom initiates
cascade reactions by nucleophilic attack on a covalently attached
benzyne. The benzynes are produced by thermal cyclization of triynes
via hexadehydro-Diels–Alder reaction. The initially produced
oxocarbenium/aryl carbanionic zwitterion is protonated in situ by
an external protic nucleophile (NuH) of appropriate acidity. The resulting
ion pair (oxocarbenium+/Nu–) collapses
through several different mechanistic manifolds, adding to the diversity
of structural classes that can be generated.