Stereoselective preparation of (E)-ε-nitro-β,γ-unsaturated methyl esters: Amberlyst A 27, using microwave, as superior catalyst for the 1,6-conjugate addition of nitroalkanes to methyl 1,3-butadiene-1-carboxylate

1,6-Conjugate addition of nitroalkanes to methyl 1,3-butadiene-1-carboxylate, performed with Amberlyst A 27, using microwaves and in the absence of any solvent, allows the prevalent formation of the β,γ-unsaturated adduct, over the α,β-unsaturated one. The products were exclusively obtained as (E)-isomers.