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).