In contrast to the low dienophilicity generally observed for α, β-unsaturated lactones, the title compound 2 is shown to be a reactive dienophile. Under stannic chloride catalysis, it undergoes Diels-Alder reaction region-and stereoselectively with a variety of dienes at room temperature. The synthesis of (±)-o-mentha-1, 3-dien-1→ 8-olide (20) has been achieved by a two-step sequence using lactone ester 2. Addition of 2 to 1-acetoxy-1, 3-butadiene ...
