Scheme 6. (a) Oxidation/olefination of alcohol 17h resulting in unexpected rearrangement of aldehyde 18h. (b) Electronic structure calculations for proposed rearrangement (UB3LYP/6-31G*, Spartan'10, gas phase, kcal mol^–1). Conditions: (i) BAIB (1.1 eq.), TEMPO (10 mol%), DCM (3 mL), (ii) Ph₃P CHCO₂Et (1.3 eq.) (one pot).