Carbocyclization reactions of terminally difluorinated alkenyl active methine compounds mediated by SnCl4 and amine

Carbocyclization of terminally difluorinated 3-butenyl active methine compounds 1a–1e proceeded through the 5-endo mode, upon treating with SnCl4 and triethylamine to give fluorocyclopentene derivatives 3a–3e. Iodocarbocyclization of dimethyl 2-(4,4-difluorobut-3-enyl)malonate (1a) mediated by I2, SnCl4 and amine provided 2,2-difluoro-3-iodocyclopentane-1,1-dicarboxylate 4a through the 5-endo mode, while in the case of 2-(5,5-difluoropent-4-enyl)malonate (1f) 5-exo mode cyclization reaction took place to give difluoroiodomethylcyclopentane derivative 5f.