A imidazole

Pyrazolo[3,4-d][l,2]diazepines synthesis, 7, 597 Pyrazolop, 4- 6][ 1,4]diazepines synthesis, 5, 272 Pyrazolo[l, 4]diazepinones as anticonvulsant, 1, 170 Pyrazolo[2,3-e]diazepinones synthesis, 5, 272 1 H-Pyrazolo[l,5-6]imidazoles synthesis, 6, 992 Pyrazolo[2,3-a]imidazoles biological activity, 6, 1024 Pyrazolo[2,3-c]imidazoles reactions, 6, 1041 synthesis, 6, 1047 Pyrazolo[2,3-imidazoles synthesis, 6, 991 Pyrazolo[3,2- njisoquinolines synthesis, 5, 339 Pyrazolop, 4-c]isoquinolines synthesis, 5, 273 Pyrazolonaphthyri dines synthesis, 5, 339 Pyrazolone, diazophotolysis, 5, 252 Pyrazolone, 4,4-dihalo-rearrangements, 5, 250 Pyrazolone, ethoxy-hydrazinolysis, 5, 253 Pyrazolone, 4-halo-... 

By condensation of 1-acetylimidazole or l-(l-pentin-4-oyl)imidazole with dimethyla-cetyl-enedicarboxylate at higher temperature, 7/f-pyrrolo[l, 2-a]imidazoles are formed along with dimethyl(imidazol-l-yl)fumarate tl58],[157]... 

Iron, Fe2+ (d6) 6, octahedral A-Imidazole, porphyrin Dioxygen transport in hemoglobin and myoglobin... 

A diastereoselective dipolar cycloaddition of chiral nitrone 80 with alkene dipolarophiles afforded imidazo[ 1,2-3]-isoaxazole (Scheme 9). The conversion via N-O reduction of this ring system with Raney-Ni in methanol gave the corresponding pyrrolo[l,2-A imidazole in 66% yield. The structure has been confirmed by X-ray diffraction crystal stmcture analysis <2000SL967>. 

Table 1 Preparation of various dihydro-1 H-pyrrolo[1,2-a]imidazole-2,5-diones...

H-lmidazo[1,2-b]pyrazole 1H-lmidazo[1,2-a]imidazole lmidazo[2,1-b]thiazole... 

Introduction of the azido group into the azine heterocycle can also be accomplished starting with azine derivatives bearing a five-membered heterocycle as a leaving group in this position. Table 8 shows three such conversions where the leaving groups are isoxazolone (entry a), imidazole (entry b), and triazole (entry c) substituents. 

A related series of diaryl pyrrolo[l,2-a]imidazoles, represented by SK F 104351 (149), 104493 (150) and 105809 (151), has been reported to show similar profiles [360,366]. In mice and rats, SK F 105809 was a prodrug for the active methyl sulphide SK F 105561 (152), which was about 10-fold more potent in vitro than SK F 86002 [367]. The in vivo profile of SK F 105809, which is reported to be in clinical trials, was similar to that of SK F 86002. 

Copper, Cu (d °), Cu " (d ) 3, trigonal planar A-Imidazole Electron transfer in Type III heme-copper oxidases (Cub in cytochrome c oxidase, for example)... 

The nitrogen rr-electron analogue of indolizine, pyrrolo[l,2-a]-imidazole [180], shows more complicated protonation behaviour... 

Alekseeva et al. (1972b) have carried out a comparison of calculated values of localization energies and free valency indices of pyrrolo[ 1,2-a] imidazole, pyrrolo[l,2-a] benzimidazole and indolizine. In all these molecules the a-position of the pyrrole ring is calculated to be more reactive than the / -position. The free valence indices increase in the order indolizine < pyrrolobenzimidazole < pyrroloimidazole, which is also the order of increasing basicity. 

The previously published results [142, 143] devoted to the synthesis of thiazolo [3,2-a]imidazol-2-ones attracted attention of Krasovskii et al. [144] to synthesize corresponding ylidene derivates and to investigate biological activities, promising to be interesting for the medicinal chemistry. By heating 2-aminothiazoles with ethyl bromacetate and a variety of aromatic aldehydes at the appropriate temperature (either 80°C or reflux) in the glacial acetic acid with anhydrous sodium acetate, ylidene derivates of structures 102-104 were isolated (Scheme 48). 

The key step of this MCR according to the opinion of the authors is an interaction of bromacetic ester with aminoazole via ring nitrogen atom to the 3-carboxymethyl-2-iminothiazoline 105, also isolated as a product in the steps-sequence reaction (Scheme 49). Further cyclization of 105 leads to the formation of thiazolo[3,2-a] imidazol-6-one 106, which then reacts with aldehyde affording the desired ylidene in moderate-to-good yields. 

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