High-Pressure Cycloaddition Reaction of Tropone with Furans

Abstract
Thermal reactions of tropone with furan and 2-methoxyfuran mainly gave the endo-[4+2] cycloadducts, the kinetically controlled products, at 3000 bar. In the latter case, the product further reacted with tropone to yield 2:1-adducts. On the other hand, the reaction with 3,4-dimethoxyfuran under similar conditions yielded mainly the exo-[4+2] adducts, the thermodynamically controlled products. The predominant formation of the endo-Diels–Alder adducts with furans under the high-pressure conditions may be valuable from a synthetic point of view.