3- Aryl-imidazole 1-oxides

Several of the methods used for synthesis of 3-alkyl or aryl-imidazole 1-oxides 228 can be modified to produce 3-hydroxyimidazole 1-oxides 267 by replacing an amine or imine functionality in the starting materials with an oxime group. 

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-... 

S-group removal from, 5, 446 oxidation, 5, 446 Imidazole, 5-aryl-4-nitroso-furazans from, 6, 417... 

Several approaches to the 1,2,3-triazole core have been published in 2000. Iodobenzene diacetate-mediated oxidation of hydrazones 152 led to fused 1,2,3-triazoloheterocycles 153 <00SC417>. Treatment of oxazolone 154 with iso-pentyl nitrite in the presence of acetic acid gave 1,2,3-triazole 155, a precursor to 3-(W-l,2,3-triazolyl)-substituted a,P-unsaturated a amino acid derivatives <00SC2863>. Aroyl-substituted ketene aminals 156 reacted with aryl azides to provide polysubstituted 1,23-triazoles 157 <00HC387>. 2-Aryl-2T/,4/f-imidazo[43-d][l,2,3]triazoles 159 were prepared from the reaction of triethyl AM-ethyl-2-methyl-4-nitro-l//-imidazol-5-yl phosphoramidate (158) with aryl isocyanates <00TL9889>. 

Imidazole was converted by hydrogenation over platinum oxide in acetic anhydride to 1,3-diacetylimidazolidine in 80% yield, and benzimidazole similarly to 1,3-diacetylbenzimidazoline in 86% yield [480. While benzimidazole is very resistant to hydrogenation over platinum at 100° and over nickel at 200° and under high pressure, 2-alkyl- or 2-aryl-substituted imidazoles are reduced in the benzene ring rather easily. 2-Methylbenzimidazole was hydrogenated over platinum oxide in acetic acid at 80-90° to 2-methyl-... 

Iodination reagents combined with aryl phosphines and imidazole can also effect reductive conversion of diols to alkenes. One such combination is 2,4,5-triiodoimidazole, imidazole, and triphenylphosphine.215 These reagent combinations are believed to give oxyphosphonium intermediates which then serve as leaving groups, forming triphenylphosphine oxide as in the Mitsunobu reaction (see Section 3.2.4). The iodide serves as both a... 

Since its discovery by Chandross and to this day, peroxy-oxalate chemiluminescence has been controversial because of its enormous complexity in view of the many alternative steps involved in this process. The principal mechanistic feature of the peroxy-oxalate chemiluminescence pertains to the base-catalyzed (commonly imidazole) reaction of an activated aryl oxalate with hydrogen peroxide in the presence of a chemiluminescent activator, usually a highly fluorescent aromatic hydrocarbon with a low oxidation potential . A variety of putative high-energy peroxide intermediates have been proposed for the generation of the excited states . In the context of the present chapter, it is of import to mention that recent work provides experimental evidence for the intervention of the 1,2-dioxetanedione 18 (Scheme 11) as the high-energy species responsible for the chemiexcitation. Furthermore, clear-cut experimental data favor the CIEEL mechanism as a rationalization of the peroxy-oxalate chemiluminescence . 

The oxidation of 42 and its aryl-substituted analogs to give dimers containing 1H-, 2H-, and 4//-imidazole residues was discussed in the previous review. Opinions differ as to the structures of certain of the products, although that from hexacyanoferrate(III) oxidation in benzene is the 1,2 -isomer. ... 

Since formamide is a weak nucleophile, the use of imidazole or 4-dimethylaminopyridine (DMAP) is necessary for acyl transfer to formamide via an activated amide (imidazolide) or acylpyridinium ion. As Scheme 22 illustrates, the reaction starts with the oxidative addition of aryl bromide 152 to Pd(0) species, followed by CO insertion to form acyl-Pd complex 154. Imidazole receives the aroyl group to form imidazolide 155 and liberates HPdBr species. Then, imidazolide 155 reacts with formamide to form imide 156. Finally, decarbonylation of imide 156 gives amide 157. In fact, the formations of imidazolide intermediate 155 and imide 156 as well as the subsequent slow transformation of imide 156 to amide 157 by releasing CO were observed. This mechanism can accommodate the CO pressure variations observed during the first few hours of aminocarbonylation. When the reaction temperature (120 °C) was reached, a fast drop of pressure occurred. This corresponds to the formation of the intermediary imide 156. Then, the increase of pressure after 3 h of reaction was observed. This phenomenon corresponds to the release of CO from imide 156 to form amide 157. ... 

Like many of the nitrogen heterocycles possessing tetrahydroxybutyl side-chains (which tend to form anhydrides), the unsubstituted imidazoline-2-thione 92 readily loses water on heating its aqueous solution under pressufe,97 to give 93, and as with other 1-substituted 2-thiones, it is converted into the 1-aryl-4-(D-arabino-tetrahydroxyl-butyl)imidazole (94) by desulfurization followed by oxidation of the product with oxygen in the presence of a platinum catalyst.98... 

The selective arylation of azoles, including imidazole, was achieved by Sames. Under the developed conditions, including the use of magnesium oxide as base, imidazole was arylated in the 4-position selectively, while the addition of a stoichiometric amount of copper(I) iodide led to the reversal of the regiochemistry, resulting in the selective formation of 2-phenylimidazole (6.89.),120... 

In relation to enzymic cytochrome P-450 oxidations, catalysis by iron porphyrins has inspired many recent studies.659 663 The use of C6F5IO as oxidant and Fe(TDCPP)Cl as catalyst has resulted in a major improvement in both the yields and the turnover numbers of the epoxidation of alkenes. 59 The Michaelis-Menten kinetic rate, the higher reactivity of alkyl-substituted alkenes compared to that of aryl-substituted alkenes, and the strong inhibition by norbornene in competitive epoxidations suggested that the mechanism shown in Scheme 13 is heterolytic and presumably involves the reversible formation of a four-mernbered Fev-oxametallacyclobutane intermediate.660 Picket-fence porphyrin (TPiVPP)FeCl-imidazole, 02 and [H2+colloidal Pt supported on polyvinylpyrrolidone)] act as an artificial P-450 system in the epoxidation of alkenes.663... 

The aromatic imidazole 1-oxides 228 discussed in Section 3.1 are derived from imidazoles 248 by appending an oxygen atom to the pyridine type ring nitrogen atom of the imidazole nucleus. The second nitrogen atom of the imidazole ring can be attached to an alkyl or aryl group or to a... 

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