Synthesis of 2-Aryl- and 6-Heteroaryl-1,3-di(4-pyridyl)azulenes by Katritzky’s Pyridylation of 2-Aryl- and 6-Heteroarylazulenes
摘要:
Preparation of 2-aryl- and 6-heteroarylazulenes 2-6 and 8-10 was established by the palladium-catalyzed cross-coupling reaction of the corresponding haloazulenes with lithium aryl- and heteroarylmagnesium ate complexes, which were readily prepared from the corresponding aryl and heteroaryl halides. The reaction of 2-6 and 8-10, except for 3 and 8, with pyridine in the presence of Tf2O, followed by treatment with KOH in MeOH afforded the corresponding 2-aryl- and 6-heteroary1-1,3-di(4-pyridyl)azulenes 11-16 in good yields.
method for the synthesis of 1- and 2-pyridylazulenes, and of 1,3-dipyridylazulenes, is described. Color and spectral changes of these pyridylazulenes upon the addition of either acid or metal ions were investigated in detail. The color changed from blue to red upon the addition of trifluoroacetic acid or soft metal ions, depending on the substitution patterns of the pyridyl group on the azulene skeleton