DISSYMMETRY OF CERTAIN SUBSTITUTED DIPYRIDOTETRAAZAPENTALENES

Article abstract of DOI:10.1016/S0040-4020(01)87674-2

In a two-step synthesis from staring amines, a series of compounds has been prepared in which steric crowding (1b,c,d,f) was introduced into the "bay region" of pyrido<1",2":1',2'>imidazo<4',5':4,5>imidazo<1,2-a>pyridine (1a).This forces the tetracyclic ring system into non-planarity.Two hexa-heterohelicenes 2a and b were prepared that incorporate the 1,3,4,6-tetraazapentalene ring system and provide molecular crowding in the "bay region" due to the terminal rings, which similarly distort the hexacyclic ring system from planarity.Single crystal X-ray structure determinations revealed that the compounds (1b,c,d,f,2a and b) exist as enantiomeric pairs in the crystalline state.