Intramolecular [4+2] trapping of a hexadehydro-Diels–Alder (HDDA) benzyne by tethered arenes

We report here the efficient, intramolecular trapping in a Diels–Alder (DA) sense of thermally generated benzynes by one of two pendant arene rings. A more electron-rich ring (p-methoxyphenyl) reacted substantially faster than a simple phenyl ring, which was, in turn, slightly more reactive vs a 4-carbomethoxyphenyl ring. Photoinduced di-π-methane rearrangement of the initial DA adducts gave rise to unusual isomeric polycyclic adducts.