Rearrangement of fused tetracyclic heterocycles induced by alkyl halides and formation of a new type of ‘proton sponge’

Intramolecular criss-cross cycloaddition of 3-substituted symmetrical homoallenyl azines 2 by heating in xylene lead to 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 6 with signs of the molecule corresponding a ‘proton sponge’ moiety was created. The scope of the rearrangement and reaction products structure was investigated.