Aza-Diels-Alder Reaction Between 1,2-Diaza-1,3-dienes and β-Aryl-α,β-unsaturated Carbonyl Compounds. Easy One-pot Entry to 2’-Oxo-imidazo[1’,5’- f]tetrahydropyridazine

1,2-Diaza-1,3-dienes bearing electron withdrawing groups react with α,β-unsaturated carbonyl compounds by means of an uncommon aza-Diels-Alder reaction furnishing functionalized tetrahydropyridazines. The regioselectivity of the process is governed by the nature of the β substituent of the α,β-unsaturated carbonyl compounds. In the case of β aryl-α,β-unsaturated carbonyl compounds the formed tetrahydropyridazines present the carbonyl group in a suitable position to undergo a further cyclization process that furnish new 2’-oxo-imidazo[1’,5’-f]tetrahydropyridazine derivatives.