Imidazole, arylation

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-... 

Classic A/-heterocychc ligands, eg, bipyridyl (bipy), terpyridyl, imidazole, pyrazine, phenanthroline, piperazine (including alkyl- and aryl-substituted derivatives), and polypyrazol-l-yl-borates (bis, tris, and tetra), have all been found to coordinate Th(IV) chlorides, perchlorates, and nitrates. The tripodal hydrotris(pyrazolyl)borates, HBPz, have been used to stabilize organometaHic complexes (31). Bis-porphyrin Th(IV) "sandwich" complexes have been... 

Phenols. Phenols are unreactive toward chloroformates at room temperature and at elevated temperatures the yields of carbonates are relatively poor (< 10%) in the absence of catalysis. Many catalysts have been claimed in the patent Hterature that lead to high yields of carbonates from phenol and chloroformates. The use of catalyst is even more essential in the reaction of phenols and aryl chloroformates. Among the catalysts claimed are amphoteric metals or thek haUdes (16), magnesium haUdes (17), magnesium or manganese (18), secondary or tertiary amines such as imidazole (19), pyridine, quinoline, picoline (20—22), heterocycHc basic compounds (23) and carbonamides, thiocarbonamides, phosphoroamides, and sulfonamides (24). 

Data taken from <71pmhi3i297), which contains references to the original literature. Simple alkyl- and aryl-imidazoles. iV-Unsubstituted compounds are IV-acylated prior to injection. 

N-Arylation of azoles is achieved either by using arynes, activated halobenzenes (e.g. dinitro) or under Ullmann conditions. Thus benzyne reacts with imidazoles to give N-arylimidazoles (70AHC(12)103), and these compounds have also been prepared under modified Ullmann conditions. 

Electrophilic substitution occurs readily in Af-phenyl groups, e.g. 1-phenyI-pyrazoIes, -imidazoles and -pyrazolinones are all nitrated and halogenated at the para position. The aryl group is attacked preferentially when the reactions are carried out in strongly acidic media, where the azole ring is protonated. 

Amidines and related systems such as guanidines react with a-halogenoketones to form imidazoles. a-Hydroxyketones also take part in this reaction to form imidazoles, and a variety of substituents can be introduced into the imidazole nucleus by these procedures. Reaction of the a-halogenoketone (73) with an alkyl- or aryl-substituted carboxamidine (76) readily gave the imidazole (77) (01CB637, 48JCS1960). Variation of the reaction components that successfully take part in this reaction process is described in Chapter 4.08. 

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

Imidazole, 2-aryl-4-phenyl-5-trifluoromethyl-synthesis, 5, 483 Imidazole, azido-reactions, 5, 442 Imidazole, 2-azido-, 5, 415 cyclization, 6, 980 reactions, 5, 96 with sodium, 5, 442 tautomerism, 5, 371 Imidazole, benzoyl-IR spectra, 5, 30 Imidazole, 2-benzoyl-4-phenyl-... 

Reaction of p-nitrophenyl 2-(p-tolylsulfinyl)acetate 161 with aryl aldimines in the presence of imidazole was found to give /j-lactams 162 and amides 163206. In the cyclization, only the two 3,4-trans derivatives were formed out of a possible four diastereomeric pairs and, interestingly, the ratio of two diastereomeric pairs went up to 6.7 1. This means not only that internal asymmetric induction207 affords the trans derivative, but that also a relatively high asymmetric induction took place during the reaction. 

A number of microwave-assisted multicomponent methods for the synthesis of imidazoles have been reported [68-71 ]. The irradiation of a 1,2-diketone and aldehyde with ammonium acetate in acetic acid for 5 min at 180 °C in a single-mode reactor provides alkyl-, aryl-, and heteroaryl-substituted imidazoles 39 in excellent yield (Scheme 14) and this method has been used for the rapid and efficient preparation of two biologically active imidazoles, lepidiline B and trifenagrel [68]. 

Ru—C(carbene) bond distances are shorter than Ru—P bond lengths, but this can simply be explained by the difference in covalent radii between P and The variation of Ru—C(carbene) bond distances among ruthenium carbene complexes illustrates that nucleophilic carbene ligands are better donors when alkyl, instead of aryl, groups are present, with the exception of 6. This anomaly can be explained on the basis of large steric demands of the adamantyl groups on the imidazole framework which hinder the carbene lone pair overlap with metal orbitals. Comparison of the Ru—C(carbene) bond distances among the aryl-substituted carbenes show... 

The reaction of 1-amino-1-deoxyketoses, and their N-alkyl and N-aryl derivatives, with alkyl or aryl isothiocyanates (Huber et al, 1960) was studied in more detail, and new 4-(alditol-l-yl)-l-alkyl(aryl)-3-alkyl(aryl)-l,3-dihydro-2H-imidazole-2-thiones were obtained. These compounds were used as starting materials for the synthesis of OL-histidines, DL-histidine-2-thiol, and other imidazole derivatives of biological interest. 

H). On the other hand, the synthesis of unsymmetricaUy iV,iV -substituted congeners is less straightforward as a functionalised imidazole has to be isolated prior to alkylation or arylation. Two main methods are available for imidazole functionaU-sation deprotonation with metalUc Na or K leading to an imidazoUde (I) followed by reaction with RX or reaction of glyoxal with a primary amine, an ammonium salt and formaldehyde (J). Al-functionalised imidazole can then be alkylated or... 

Nevertheless, the placement of two Cl atoms on the C and C carbon atoms of the NHC skeleton, the presence of the strong SO Ar electron-withdrawing group on the aryl A-substituents, or the modification of the NHC skeleton from an imidazol-to a triazol-type, have allowed to fill the gap between the TEP of phosphines and NHCs, see Pig. 1.14. 

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