'Inverse-electron-demand' Diels-Alder reactions of (E)-3-diazenylbut-2-enes in water

The cycloadditions of (E)-3-diazenylbul-2-enes 1 with a variety of alkenes 2-6 were carried out in water as well as in organic solvents. The reactions were always faster in heterogeneous aqueous medium than in the organic sol vents. These conjugated diazenyl-alkenes behave mainly as heterodienes. and the Diels-Alder adducts are the sole or at least main reaction products. P yrroles derived from zwitterionic [3 + 2] cycloaddition reactions were obse rved in some cases. The cycloaddition of 1a with (+)-2-(ethenyloxy)-3,7,7-t rimethylbicycloclo[4.1.0]heptane (5) is the first example of an asymmetric 'inverse electron-demand' Diels-Alder reaction carried out in pure water.