5-Methyl-2-(pyridin-3-yl)-4,5-dihydrooxazole and 5-methyl-2-(pyridin-4-yl)-4,5-dihydrooxazole
activated by triflic anhydride underwent lactonization with bis(trimethylsilyl)ketene
acetals to provide tetrahydrooxino[3,4-c]pyridines and tetrahydrofuro[3,2-b]pyridin-2-ones. Formation of the product was controlled by the position of the pyridyl
substituent at C-3 and C-4 of the pyridyldihydrooxazole. On the other hand, 1-(trifluoromethylsulfonamido)propan-2-yl
picolinate was obtained under the same conditions from 5-methyl-2-(pyridin-2-yl)-4,5-dihydrooxazole.
Key Words
lactonization - pyridyldihydrooxazoles - ketene acetals - spirotetrahydrofuro[3,2-
b]pyridin-2-ones - spirotetrahydrooxino[3,4,-
c]pyridines