Chemo, regio, and stereoselectivity in olefination of hydrazone 1,4-adducts between conjugated azoalkenes and sulphur co-activated methylene compounds

In the presence of sodium methoxide in catalytic amount, conjugated azoalkenes smoothly add at room temperature (phenylsulphonyl)acetamide, methyl (phenylsulphonyl)acetate, methyl (phenylsulphinyl)acetate, (arylsulphonyl)acetonitriles, bis(phenylsulphonyl)methane, and (arylsulphonyl)nitromethane to yield the corresponding α-functionalized hydrazone derivatives by 1,4-addition. In some cases these hydrazones were isolated, while in others their formation is accompanied by olefination products. Under the same reaction conditions and/or in methanol by means of gentle heating, several of these adducts give rise to the related α,β-olefinated hydrazone derivatives as pure isomeric forms or as EE EZ mixtures by loss of the nitro, sulphonyl or sulphinyl group. It is noteworthy that for β-cyano-β-arylsulphonyl adducts it was mainly detected the elimination of the arylsulphonyl group affording β-cyano-α,β-olefinated hydrazones, while for analogous β-nitro-β-arylsulphonyl adducts it was principally observed the loss of the nitro moiety producing β-arylsulphonyl-α,β-olefinated hydrazones.