2,3,4,5-Tetraphenyl-imidazole 3-oxide

Tetraphenyl-imidazole 3-oxide 256 (R, R1, R2, R3 = Ph) upon irradiation in methanol solution isomerized to give (Z,Z)-benzil diimine (1979AJC2059). 

Bei 1-substituierten Imidazolen scheint die Ringoffnung im allgemeinen bevorzugt zu sein. So fiihrt die Oxidation von 1,2,4,5-Tetraphenyl-imidazol mit Singulett-Sauerstoff in Methanol in 97% Ausbeute zu N,N-Dibenzoyl-N-phenyl-benzamidin1233. 

Under ideal conditions, epoxidations with homogeneous or anchored Mn and Fe porphyrin catalysts are characterized by high numbers of turnovers and high stereospecificities (104-106,116,117,130,131). For example, 93% cz s-epoxide was obtained from dx-stilbene, with H2O2 and Fe-tetraphenyl-porphyrin on imidazole-modified SiCU (106). Various oxidants, including NaOCl, can be used (117) ... 

Necessary conditions for synthetic models to mimic oxyhemoglobins are formation of a five-coordinate heme precursor with a proximal base (e.g., imidazole, pyridine), prevention of p-peroxo/p-oxo (M-02-M/M-0-M) dimer formation upon oxygenation (i.e., reversible oxygenation), and exclusion of protons and nucleophiles. Model systems should be easily modified and allow probing of distal and proximal influences. Tetraphenyl-porphyrins (TPP) serve as the basis of numerous model complexes, because they are less susceptible to oxidation... 

Upon oxidation with potassium ferricyanide the imidazole was converted in 91% yield to 2,2 -bis(2,4-dime-thoxyphenyl)-4,4, 5,5 -tetraphenyl-I,2 -biimidazole, a pale green phototropic solid. Analysis of a portion of the product which was isolated in an unsolvated state was ... 

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