Highly fluorinated heterocycles. Part XIX. Dehydrofluorination studies on 2-dipluoromethyl- and 2-trifluoromethyl-hexa- and -pentafluoro-oxolans

Abstract The four 3H, 4H-2-difluoromethylpentafluoro-oxolans reacted with powderedpotassium hydroxide in suspension in benzene to give 3H- (1) and 4H- (2)2-difluoromethyltetrafluoro-3,4-oxolen, different proportions being formedfrom each stereoisomer. 3H/4H- and 4H/JH-2-Trifluoromethylpentafluoro-oxolanslikewise afforded different proportions of 3H- (3) and 4H- (4) 2-trifluoromethyltetrafluoro-3,4-oxolen.From similar dehydrofluorinations of mixedisomers of 3H- and 4H- 2-difluoromethylhexafluoro-oxolan, there were formed2-difluoromethylpentafluoro-3,4- (5) and -2,3- (6) oxolen; mixed 3H- and4H-2-trifluoromethylhexafluoro-oxolan afforded an inseparable mixture of 2-trifluoromethylpentafluoro-3,4- (7a) and -2,3- (7b) oxolen. With cobalticfluoride, oxolen (5) gave 2-difluoromethylheptafluoro-oxolan (8). On treatmentwith aqueous potassium hydroxide, (8) underwent ring-opening, formingtetrafluoropent-2-en-l,5-diolc acid (10). Diels-Alder adducts resulted fromreactions of oxolen (Ta) with cyclopentadiene and with furan.