Condensation of 3-methyl-2-butanone and methylcyclohexyl ketone with trioxane in trifluoro-(trichloro)acetic acid yields 2,2-dialkyl-3-oxo-1-butyl trifluoro(trichloro)acetates. Treating of these compounds with N-ethylanilinomagnesium bromide gives 5,5-dialkyl-2-hydroxy-2-trifluoro(trichloro)methyl-4-tetrahydropyrones, which were dehydrated to form 5,5-dialkyl-2-trifluoro(trichloro)methyl-4-dihydropyrones.