Oxabicyclo[3.2.1]octane derivatives as highly reactive dienophiles: synthesis of bicyclo[5.n.0] systems

reaction: see text] We have developed highly versatile, homochiral oxabicyclo3.2.1]octadiene building blocks for the synthesis of natural products. We have found that these bridged alkenes undergo exceptionally facile Diels-Alder reactions and react faster than several well studied bicyclo2.2.1]heptene dienophiles. The reaction proceeds with high levels of stereochemical control and in very good to excellent yields, providing access to bicyclo5.4.0]undecane and bicyclo5.3.0]decane systems. This reactivity is attributed to strain and homoconjugation effects.