Intramolecular Rearrangements of Tertiary Amine Oxides

Intramolecular acyl transfer to an N-oxide was examined as a route to a synthetically viable thermal ester cleavage. The pyrolysis of N-piperidylethyl N-oxides indicated that where structurally feasible, other thermal reactions (Cope elimination, Meisenheimer rearrangement, and deoxygenation) will dominate over the desired acyl transfer. However, where the ester cleavage was dictated by the use of 2-picolyl ester N-oxides, acceptable yields (50-84%) of isolated acids resulted from the thermolysis (ca. 140 °C) of 2-picolyl benzoate N-oxides in the presence of anhydrous ferric chloride.