Imidazole Derivatives, III. Regiospecific Synthesis,Structure, and Fluorescence Properties of Highly substituted Imidazo[1,2‐a]pyridines and Pyrido[1,2‐a]benzimidazoles

Abstract

1‐(Arylacetyl)imidazoles 1 react with acetylenedicarboxylic esters to provide highly functionalized imidazo[1,2‐a]pyridines 2 in up to 89% yield. The scope and limitations of this novel condensation reaction have been investigated, ad a mechanistic interpretation is presented. A strong effect on the yield of this reaction is observed for electron‐donating and electronwithdrawing substituents in the para position of the aryl ring. Moreover, the transformation is shown to proceed in a regiospecific manner starting with 4,5‐unsymmetrically substituted 1‐(arylacetyl)imidazoles (1d–g) and is extended to the synthesis of the corresponding pyrido[1,2‐a]benzimidazoles 12. The crystal structure of derivative 2a has been determined by X‐ray analysis. Imidazo[1,2‐a]pyridines 2 and pyrido[1,2‐a]‐benzimidazoles 12, obtained by this procedure, are highly fluorescent in the visible region with characteristically large Stokes shifts.

Substituted Imidazonaphthyridine Derivatives. I. C19H14F3N3, C18H10F5N3, C18H11ClF3N3 and C18H11BrF3N3

“…2). Such rr-Tr interactions were also observed in the imidazopyridine derivatives (Knolker, Boese & Hitzemann, 1990). …”

A Novel Reaction of 4-(Arylmethylene)-2-phenyloxazol-5(4H)-ones with Pyridin-2-amine: Formation of 3-(Arylmethyl)-3-(benzoylamino)imidazo-[1,2-a]pyridin-2(3H)-ones

“…IR (KBr): 3268,3026,2988,1701,1669,1579,1528,823,808,755,731,584 12,167.31,166.13,148.03,142.54,138.55,134.14,132.46,132.28,131.33,128.37,128.04,124.25,120.13 116.35 114.59,112.19,76.81,42.12;DEPT (135): 142.54,134.14,132.46,131.33,128.37,128.04,124.25,120.13,116.35 114.59,112.19,42.12. Anal.…”

Iridium, ruthenium, and palladium complexes containing a mesoionic fused imidazolylidene ligand

“…Fused systems that involve one of the imidazole nitrogen atoms (B, C, Fig. 1) have been less 2 investigated [26][27][28][29][30][31][32][33], even though a variety of synthetic approaches towards such fused ligand precursor systems are available and allow for the introduction of a variety of coordination motifs [34][35][36][37][38][39][40].…”