Generation [via Tetradehydro-Diels–Alder Reactions] and Reactivity of 6‑Fluorocyclohexa-1,2,4-triene Intermediates

We report the engagement of the 2,6-difluorophenyl substituent
in tetradehydro-Diels–Alder (TDDA) reactions. The use of fluorine
was guided by DFT computations. Acceleration of TDDA cycloisomerization
by an anhydride linker in the substrates was also key. Trapping of
the strained cyclic allene intermediate by nucleophilic carbons in
external heterocycles, an enol, and alkenes led to unusual reactivities
(e.g., one rationalized by rearrangement to a carbene intermediate).