An efficient and stereocontrolled access to 1(Z),3(E)-1,4-dialkoxybutadienes is described that relies on a base-induced conjugated elimination reaction on γ-alkoxy or aryloxy R,β-unsaturated acetals. The dienes have then been applied in [4 + 2] cycloaddition reactions where they demonstrate a good thermal reactivity toward activated dienophiles. Despite the 1,4-competition between oxygenated groups, both regio-and endoselectivities are total. A set of experiments has led to the conclusion that the (1Z,3E) pattern is responsible for these high stereocontrols. Several chiral alkoxy dienes have also been prepared following the same route. Their thermal cycloaddition with N-methylmaleimide leads to corresponding adducts in good yields and with total endoselectivities, but modest diastereoisomeric excess.

A direct and stereocontrolled access to a new class of conjugated bis-dienes is presented that relies on a double conjugated−elimination reaction induced by the action of strong bases such as n-BuLi or KHMDS on bis-α,β-unsaturated acetals. These bis-dienes undergo double [4  + 2] cycloadditions with activated dienophiles under thermal conditions. With methyl acrylate, the reaction is totally endo and regiocontrolled with respect to both dienes and exhibits up to 60% inter-ring diastereocontrol when performed under high pressure. Mixed adducts can also be obtained by adding successively two different dienophiles. Again, the endo and regiocontrols are total while the ring-to-ring diastereocontrol depends on reaction conditions but remain, most of the time, relatively low. Double hetero-Diels−Alder reactions have also been performed, yielding bicyclic skeletons of novel 4↔4‘ disaccharidic structures. Finally, the corresponding nonconjugated bis-dienes have also been evaluated in cycloadditions. They react at room temperature with NMM or diethyl ketomalonate to provide highly functionalized polycyclic structures in high yields.