Construction of Substituted [4]Acene Frameworks Based on Double Cationic Cyclizations of Fluoroalkenes

Abstract In this study, 5-substituted and 5,6-disubstituted [4]acenes were synthesized by the double cationic cyclization of fluoroalkenes. (a) After being treated with Me2AlCl (1.2 equiv), 2-trifluoromethyl-1-alkenes bearing two aryl groups underwent domino Friedel–Crafts-type (two-ring construction) followed dehydrogenation to generate 5-fluorinated [4]acenes. The same (trifluoromethyl)alkenes both equiv) Me3Al (1.0 resulting in selective one-ring construction creation bicyclic 1,1-difluoro-1-alkenes. (b) When triflic acid, difluoroalkenes regioselective protonation CF2 cations; these cations provided tetracyclic ketones. obtained ketones act as an appropriate platform for introduction substituents at 5-position (c) DDQ/H+, oxidative generation allylic produced enones. enones subjected addition carbanions facilitate 5- 6-positions dihydro[4]acenes.