Studies toward the Synthesis of Oximidines I and II

The synthesis of compound 1, a precursor for the synthesis of the oximidine II core structure 2, is described. An undesired C8−C9 isomerization occurred during the intramolecular Castro−Stephens reaction leading to macrocyle 3. The thermodynamic driving force for this unexpected isomerization was established by DFT and MP2 calculations.