Favoring trienamine activation through unconjugated dienals: organocatalytic enantioselective remote functionalization of alkenes.

Unconjugated 2,5-dienals are more reactive substrates than the corresponding fully conjugated α,β,γ,δ-unsaturated aldehydes towards organocatalytic activation through trienamine intermediates. This difference in reactivity has been demonstrated in the Diels-Alder reaction with nitroalkenes, a reaction that proceeds with clean β,ε-selectivity to afford the final products in high yields and stereoselectivities, the related polyconjugated 2,4-dienals being completely unreactive.