interesting fused heterocyclic systems consisting of four five-membered rings with two nitrogen atoms in the skeleton 3. These compounds 3 were found to be sensitive to attack by alkyl halides. Their presence, depending on the reaction conditions, resulted in a new type of rearrangement leading to compounds 4 and 5, respectively. With an excess of alkyl halide and in the presence of NaBH3CN a new structure
In an acidic medium the criss-cross cycloadduct 2 with four fused five-membered rings rearranges to a heterocyclic compound 3 with a completely different structure consisting of two six-membered and two five-membered rings. This newly discovered rearrangement was observed in the presence of a reducing agent (NaBH3CN). The rearrangement proceeds easily and with an extremely high yield.