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Imidazole Derivatives, VII. Reaction of 1‐Acylimidazoles with Dialkyl Acetylenedicarboxylates: Synthesis of Imidazo[1,2‐ a ]pyridines, (2‐Imidazolyl)maleates, 1,5‐Dihydroimidazo[1,2‐ a ]pyridines, Furo[2′,3′: 2,3]pyrrolo[1,2‐ a ]imidazoles, Furo[2′,3′: 2,3]pyrrolo[1,2‐ a ]benzimidazoles and 7 H ‐Pyrrolo[1,2‐ a ]imidazoles
Author(s) -
Knölker HansJoachim,
Boese Roland,
Döring Detlev,
ElAhl AbdelAziz,
Hitzemann Rainer,
Jones Peter G.
Publication year - 1992
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19921250822
Subject(s) - chemistry , imidazole , ylide , electrophile , azine , medicinal chemistry , acetonitrile , ring (chemistry) , stereochemistry , organic chemistry , catalysis
The reaction of 1‐acylimidazoles with dialkyl acetylenedicar‐boxylates provides novel functionalized imidazole derivatives by a sequence of electrophilic attack on the imidazole azine nitrogen atom and subsequent transprotonations and trans‐acylations of the ylide generated in the first step. Based on this methodology we described a condensation of 1‐arylacetylimid‐azoles with DMAD in acetonitrile providing imidazo[1,2‐ a ]pyridines. We have now achieved a control of the cyclization mode leading to a different ring system simply by varying the acyl side chain. Solvent and reaction temperature influence these cyclizations strongly, thus allowing the preparation of further novel imidazole derivatives including the hitherto unknown furo[2′,3′:2,3]pyrrolo[1,2‐ a ]imidazole framework. Changing the parameters of the reaction of 1‐alkanoylimidazoles with electron‐deficient acetylenes allows the synthesis of (2‐imidazolyl)maleates 1,5‐dihydroimidazo[1,2‐ a ]pyridines, furo[2′,3′:2,3]pyrrolo[1,2‐ a ]imidazoles, furo[2′,3′: 2,3]pyrrolo[1,2‐ a ]benzimidazoles, and 7H ‐pyrrolo[1,2‐ a ]imidazoles. The crystal structures of compounds 14a, 26 , and 31d have been determined by X‐ray analysis.