| Abstract: | The cycloadditions of (E)‐3‐diazenylbut‐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 solvents. These conjugated diazenyl‐alkenes behave mainly as heterodienes, and the Diels‐Alder adducts are the sole or at least main reaction products. Pyrroles derived from zwitterionic 3+2] cycloaddition reactions were observed in some cases. The cycloaddition of 1a with (+)‐2‐(ethenyloxy)‐3,7,7‐trimethylbicyclo4.1.0]heptane ( 5 ) is the first example of an asymmetric `inverse electron‐demand' Diels‐Alder reaction carried out in pure water. |
