Collect. Czech. Chem. Commun. 1985, 50, 1948-1958

Cleavage of 3,3,4-trifluoro-2,2-dimethyloxetane by mineral acids

Václav Dědeka and Ivan Veselýb

a Department of Organic Chemistry, Prague Institute of Chemical Technology, 166 28 Prague 6
b Spolana, 277 11 Neratovice


Cleavage of 3,3,4-trifluoro-2,2-dimethyloxetane (I) in an aqueous solution of sulphuric acid, phosphoric acid, hydrogen chloride, or hydrogen bromide gave a mixture of 2,2-difluoro-3-methyl-3-butenal (II) and 5,5-difluoro-2-(1,1-difluoro-2-hydroxy-2-methylpropyl)-4-hydroxy-6,6-dimethyl-1,3-dioxane (VIa); in the cleavage effected by hydrochloric or hydrobromic acid the mixture also contained 3-chloro- or 3-bromo-2,2-difluoro-3-methyl-1,1-butanediol (Vb or Vc). In alcoholic solutions of the mineral acids the cleavage afforded the corresponding acetals of butenal II and 2,2-difluoro-3-hydroxy-3-methylbutanal (IIIa). The action of sulphuric acid in the presence of acetyl chloride or acetanhydride led to 1-chloro-2,2-difluoro-3-methyl-3-butenyl acetate (IVd) or 2,2-difluoro-3-methyl-3-butenylidene diacetate (IVe), as the main product. Butenal II was a sole product of the cleavage of oxetane I by polyphosphoric acid at 150-160 °C in the gaseous phase. At temperatures above 180 °C there were also formed (in addition to butenal II) 1,1,5,5-tetrafluoro-2,6-dimethyl-1,6-heptadiene-4-ol (IX) and its formate (X).