Novel cycloadducts from the reactions of [α,α-bis(3,3,3-trifluoropropynyl)]benzyl benzoate and [1,1-bis(3,3,3-trifluoropropynyl)]ethyl ethanoate with furan

Abstract

Reaction of furan with the dialknyl ester (CF₃CC)₂CPhOCOPh (1a) in dichloromethane at 50°C affords a mixture of four 1:1 adducts, the (Z)-isomer of triene (4a)(major product), diketone (5a), and the benzopenta-cyclononenes (3) and (6), via the common intermediate 2-benzoyloxy-2-phenyl-4, 10-bis(trifluoromethyl)-7-oxapentacyclo [4.4.0.0^1,3.0^5,9.0^8,10]dec-3-ene (9) formed from the bis Diels–Alder adduct by intramolecular (_π2_s+_π2_s+_π2_s) cycloaddition followed by retro-cleavage of furan; the corresponding reaction with the ester (CF₃CC)₂CMeOCOMe (1b) gives analogously diketone (5b)(major product) and a mixture of the (E)- and (Z)-isomers of triene (4b), a rearranged furan–dialkyne 2:1 adduct (7) or (8) also being formed.