TfOH-Promoted Reactions of TMS-Ethers of CF3-Pentenynoles with Arenes. Synthesis of CF3-Substituted Pentenynes, Indenes, and Other Carbocyclic Structures

Trimethylsilyl ethers of 1,5-diaryl-3-( trifluoromethyl)pent-1-en-4-yn-3-oles [Ar-C.C-C(CF3)(OSiMe3)-CH.CH-Ar'] in the superacid TfOH give rise to reactive conjugated CF3-allylic-propargylic cations [Ar-C.C-C+(CF3)-CH.CH-Ar']. These species react with arenes in the presence of 1.5 equiv of TfOH forming regio- and stereoselectively E-1,1,5-triaryl-3-(trifluoromethyl)-pent-2-en4-ynes [Ar-C.C-C(CF3).CH-CHAr'(Ar '')] in good yields. In the excess of TfOH, these CF3-pentenynes are further intramolecularly cyclized into CF3-bicyclic dihydroanthracene derivatives ("helicopter"-like molecules). The CF3-pentenynes may also react with arenes, as external nucleophiles, leading to CF3-indenes. These two main reaction pathways depend on internal nucleophilicity of aryl substituents in CF3-pentenynes and external nucleophilicity of aromatic molecules. Plausible cationic reaction mechanisms have been discussed. CF3-bicyclic dihydroanthracene derivatives have been studied regarding their cytotoxicity and virus-inhibiting activity against influenza virus A/Puerto Rico/8/34 (H1N1) in MDCK cell line.