3- Substituted imidazole 1-oxide bromination

Imidazole, 2-amino-1 -methyl-4,5-diphenyl-tautomerism, 5, 368 Imidazole, 2-aroyl-mass spectra, 5, 360 synthesis, 5, 391, 402 UV spectra, 5, 356 Imidazole, 4-aroyl-synthesis, 5, 474 Imidazole, C-aroyl-UV spectra, 5, 356 Imidazole, aryl-nitration, 5, 396, 433 oxidation, 5, 433 Imidazole, 1-aryl-dipole moments, 5, 351 dearylation, 5, 449 ethylation, 5, 448 H NMR, 5, 353 hydroxymethylation, 5, 404 rearrangement, 5, 108 synthesis, 5, 390 thermal rearrangement, 5, 363 Imidazole, 2-aryl-chlorosulfonation, 5, 397 synthesis, 5, 475 Imidazole, 4-aryl-bromination, 5, 399 Imidazole, C-aryl-electrophilic substitution, 5, 432-433 nitration, 5, 433 Imidazole, N-aryl-reactions, 5, 448-449 structure, 5, 448-449 Imidazole, arylmercapto-... 

The most common reactions involving nucleophiles and porphyrin systems take place on the metalloporphyrin 77-cation radical (i.e. the one-electron oxidized species) rather than on the metalloporphyrin itself. One-electron oxidation can be accomplished electrochemi-cally (Section 3.07.2.4.6) or by using oxidants such as iodine, bromine, ammoniumyl salts, etc. Once formed, the 77-cation radicals (61) react with a variety of nucleophiles such as nitrite, pyridine, imidazole, cyanide, triphenylphosphine, thiocyanate, acetate, trifluoroace-tate and azide, to give the correspondingly substituted porphyrins (62) after simple acid catalyzed demetallation (79JA5953). The species produced by two-electron oxidations of metalloporphyrins (77-dications) are also potent electrophiles and react with nucleophiles to yield similar products. 

A third example comes from Clyne et al. [358] and concerns the axial chiral binaphthyl backbone [359,360], itself known from phosphorus chemistry [361]. The synthesis starts from the trifluoromethylsulfonato substituted binaphthyl with a Kumada coupling reaction [291,292] with methytmagnesiumbromide. Oxidation with NBS yields the methyl brominated derivative that can be attached to the imidazole ring. Subsequent methylation results in the bis-imidazolium salt that is deprotonated to the bis-carbene and coordinated to the transition metal halide (Pd, Ni), a rather straightforward reaction sequence (see Figure 3.113). The overall yield for the four-step reaction to the bis-imidazolium salt is surprisingly good (65%). 

---