On the formation and solvolysis of 4-aryl-2,2-difluoro-6-methyl-1,3,2-(2H)-dioxaborines

The condensation of aryl methyl ketones 6 with acetic anhydride 4a in the presence of the boron trifluoride-acetic acid adduct 7 gives rise to the formation of 4-aryl-2,2-difluoro-6-methyl-1,3,2-(2H)-dioxaborines 8 in satisfactory yields. The stable 4-aryl-2,2-difluoro-6-methyl-1,3,2-(2H)-dioxaborines 8 can be transformed by hydrolysis into the corresponding aroylacetones 9. The reaction was optimized so as to avoid the formation of by-products, such as 2,4-diaryl-6-methylpyrylium tetrafluoroborates 11 or self-condensation products.