Double N-arylation reaction of polyhalogenated 4,4’-bipyridines. Expedious synthesis of functionalized 2,7-diazacarbazoles

Unusual 2,7-diazacarbazoles were prepared in one step from readily available tetra-halogenated 4,4’-bipyridines by using a double N-arylation reaction in the presence of the Pd–XPhos catalyst system. Moderate to good yields were obtained in this site-selective Buchwald–Hartwig double amination. The functionalization of these tricyclic derivatives was performed by using Pd-catalyzed cross-coupling reactions such as the Stille and Suzuki couplings. Two compounds were analyzed by X-ray diffraction and show π–π stacking involving the diazacarbazole moieties and the phenyl rings of functionalized groups.


Synthesis and characterization of compounds 12.
These were obtained according to the general procedure of the double N-arylation reaction.

Crystallographic data of compound 3b
Residual density was found within the channels parallel to [010], but refinement of the disordered nhexane molecules was not successful; this is due to the fact that the n-hexane molecules are ~2.7 times longer than the crystallographic b axis. The final model was then constructed by inserting carbon atoms with partial occupancies into these channels. CCDC 818528 contains the detailed crystallographic data. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre at www.ccdc.cam.ac.ik/data_request/cif.
ORTEP-3 view of 3b in space group C2/c. Atomic displacement ellipsoids are drawn at the 50% probability level. Disordered carbon atoms of the n-hexane solvent molecule are not shown.

Crystallographic data of compound 12c
Residual density was found within the channels parallel to [100], but refinement of the disordered chloroform molecules was not successful. The final model was then constructed by inserting chlorine atoms with partial occupancies into these channels. CCDC 818527 contains the detailed crystallographic data. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre at www.ccdc.cam.ac.ik/data_request/cif.
ORTEP-3 view of 12c in space group P-1. Atomic displacement ellipsoids are drawn at the 50% probability level. Disordered chlorine atoms of the chloroform molecules are not show.