Youxiang Wang, D. Rillema
Sep 15, 1997
Citations
3
Influential Citations
25
Citations
Journal
Tetrahedron
Abstract
Abstract The preparation of a series of heterocycles obtained by the condensation of 4,5-diazafluoren-9-one with various amines is described with particular emphasis on bridged systems formed by the condensation of 4,5-diazafluoren-9-one with diamine compounds such as hydrazine. Due to sp2 hybridization of the nitrogen atom in the bridge, the protons in the two pyridine units of each bipyridine group are non-equivalent. The projection of a hydrogen atom from one of the pyridine rings into the ring current of an adjacent phenyl ring shifts the proton resonance upfield. Proton NMR resonances have been uniquely assigned for all the compounds and electronic absorptions have been attributed to π → π ∗ transitions located in the ultraviolet region of the spectrum. Reduction of the heterocycles occurs at the imine nitrogen bridge and is irreversible, except for the ligand resulting from the condensation of 4,5-diazafluoren-9-one with hydrazine.