Conjugate addition of triallylaluminum to α,β-unsaturated nitroalkenes to produce 4,5-unsaturated nitroalkenes

The reaction of aryl substituted α,β-unsaturated nitroalkenes 1a-g with triallylaluminum 2 in ether solution at 0°C generated low to high yields of 4,5-unsaturated nitroalkenes 3a-g after adding the nitronate to an ice-cold solution of dilute hydrobromic acid. The yields of products 3h-j were increased substantially when the alkyl substituted α,β-unsaturated nitroalkene 1h and the highly hindered α,β-unsaturated nitroalkenes 1i and 1j reacted with 2 in the presence of aluminum chloride. The most important thing is triallylaluminum was prepared from allyl bromide and pure elemental Al, not from Grignard reagent.