Reaction between furan and the dialkynyl ester (CF3C=C)2CPhO2CPh 1a in dichloromethane at 50-degrees-C gave four rearranged 1:1 adducts, (Z)-5-(alpha-benzoyloxybenzylidene)-1,4-bis(trifluoromethyl)-8-oxa-tricyclo[4.3.0.0(2,9)]nona-3,6-diene 11a (major product), 4-benzoyloxy-3,8-bis(trifluoromethyl)-1,1a,-2,8c-tetrahydro-4H-1,2,8b-epoxymehtenocyclopropa[c]fluorene 15, the corresponding 3H-compound 16 and 8,9-dibenzoyl-4,7-bis(trifluoromethyl)-2-oxatetracyclo[4.3.0.0.(3.5)0(4.9)] non-7-ene 13a 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 8a formed from the Diels Alder adduct by intramolecular (pi2s + pi2s + pi2s) cyclo-addition. The corresponding reaction with the ester (CF3C=C)2CMeO2CMe 1b gave analogously the diketone 13b (major product) and a mixture of the (E)- and (Z)-isomers of the triene 11b; a 2:1 adduct, 4-acetoxy-3-methyl-5,11-bis(trifluoromethyl)-8,15-dioxahexacyclo[10.2.1.0(2,11)0.(4,9)0.(5,7)0(6,10)]-pentadeca-2,13-diene 10 was also isolated. A mixture of cyclopentadiene and the ester 1a (2:1 molar ratio), heated at 50-degrees-C, yielded mainly the bis-Diels-Alder adduct alpha,alpha-bis(3-trifluoromethyl-bicyclo[2.2.1]hepta-2,5-dien-2-yl)benzylbenzoate 7a, together with the rearranged 1:1 adduct, diketone 13c. Similarly, the major product from the reaction of an excess of cyclopentadiene with ester 1b at 50-degrees-C was the bis-Diels-Alder adduct 7b, but a 1:1 molar ratio of reactants at 20-degrees-C gave the mono Diels-Alder adduct 1-(3-trifluoromethylbicyclo[2.2.1]hepta-2,5-dien-2-yl)-1-(3,3,3-trifluoropropynyl) ethyl ethanoate 6d in high yield. The bis adduct 7a was stable at 50-degrees-C, but the mono adduct 6d underwent slow intramolecular (pi2s + pi2s + pi2s) cycloaddition, cf., the furan reactions, and the intermediate 8d so formed rearranged to a mixture of 8,9-diacetyl-4,7-bis(trifluoromethyl)-tetracyclo[4.3.0.0(3,5)0(4,9)]non-7-ene 13d and 1-acetoxy-1-[4,7-bis(trifluoromethyl)tetracyclo-[4.3.0.0.(3,5)0(4,9)]non-7-en-9-yl]ethene 18. In the presence of traces of water, the ketone 13d was only a minor product with the major products being the substituted ethene 18 and two diastereoisomers of 1-acetoxy-1-[4,7-bis(trifluoromethyl)tetracyclo[4.3.0.0.(3,5)0(4,9)] non-7-en-9-yl]ethanol 19.
