Diphenylimidazole

Theoretical studies of the relative stabilities of tautomers 14a and 14b were carried out mostly at the semiempirical level. AMI and PM3 calculations [98JST(T)249] of the relative stabilities carried out for a series of 4(5)-substituted imidazoles 14 (R = H, R = H, CH3, OH, F, NO2, Ph) are mostly in accord with the conclusion based on the Charton s equation. From the comparison of the electronic spectra of 4(5)-phenylimidazole 14 (R2 = Ph, R = R3 = H) and 2,4(5)-diphenylimidazole 14 (R = R = Ph, R = H) in ethanol with those calculated by using ir-electron PPP method for each of the tautomeric forms, it follows that calculations for type 14a tautomers match the experimentally observed spectra better (86ZC378). The AMI calculations [92JCS(P1)2779] of enthalpies of formation of 4(5)-aminoimidazole 14 (R = NH2, R = R = H) and 4(5)-nitroimidazole 14 (R = NO2, R = R = H) point to tautomers 14a and 14b respectively as being energetically preferred in the gas phase. Both predictions are in disagreement with expectations based on Charton s equation and the data related to basicity measurements (Table III). These inconsistencies may be... 

Whereas the cycloaddition of arylazirines with simple alkenes produces A -pyrrolines, a rearranged isomer can be formed when the alkene and the azirine moieties are suitably arranged in the same molecule. This type of intramolecular photocycloaddition was first detected using 2-vinyl-substituted azirines (75JA4682). Irradiation of azirine (54) in benzene afforded a 2,3-disubstituted pyrrole (55), while thermolysis gave a 2,5-disubstituted pyrrole (56). Photolysis of azirine (57) proceeded similarly and gave 1,2-diphenylimidazole (58) as the exclusive photoproduct. This stands in marked contrast to the thermal reaction of (57) which afforded 1,3-diphenylpyrazole (59) as the only product. 

The irradiation of 3,5-diphenylisoxazole in the presence of propylamine gave a mixture of 2,5-diphenyloxazole (20%) and A-propyl-2,5-diphenylimidazole (1%). The same distribution of the products was obtained starting from the azirine 46 (75T785). 

Potassium 4,5-diphenylimidazolate with [Cp RuCl] gives the trimer 52 containing the X-T T mode (OOOM5263), which under reflux gives the r -coordi-nated species 53 (R = R = Ph, R = H). The structure of the latter was confirmed by X-ray analysis. In similar conditions 2,4-dimethylimidazole gives species 53 (R = R = Me, R = H) straightforwardly. 

Diphenylimidazole with palladium acetate forms the cyclometallated complex 80 (X = OAc) (97AOC491). The acetate group is replaced by chloride or bromide when 80 (X = OAc) reacts with sodium chloride or lithium bromide, respectively, to give 80 (X = C1, Br). Bromide with diethyl sulfide forms the mononuclear complex 81. Similar reactions are known for 1 -acetyl-2-phenylimidazole (96JOM(522)97). 1,5-Bis(A -methylimidazol-2-yl)pen-tane with palladium(II) acetate gives the cyclometallated complex 82 (OOJOM (607)194). 

Diethylzinc l,3-bis(l-adamantyl)imidazol-2-ylidene adduct is known (93JOM(462)13). Bis(l,3-diphenylimidazol-2-ylidene) mercury(II) carbene complexes follow from the corresponding imidazolium perchlorate and mer-cury(II) chloride (68AGE682). 

Collman JP, Hutchison JE, Lopez MA, Tabard A, Guilard R, Seok WK, Ibers JA, L Her M. 1992. Synthesis and characterization of a superoxo complex of the dicobalt cofacial diporphyrin [(/u,-02)Co2(DPB)(l,5-diphenylimidazole)2][PF6], the structure of the parent dicobalt diporphyrin Co2(DPB), and a new synthesis of the free-base cofacial diporphyrin H4(DPB). J AmChemSoc 114 9869. 

With the phosphoric imidazolides D, E, and F, dehydration of the aldoximes can also be achieved (dioxane, room temperature, several hours). With diphenylimidazole-1-phosphonate (D) and phenyldiimidazole-l,l -phosphinate (E) the yields of nitriles are always higher than with (C6H50)2P(0)C1 and C6H50P(0)C12 however, with phosphoryl triimidazole (F) the yields are a little lower than with POCl3.[9] Spin-labeled phosphoric imidazolides of this type are also used for the dehydration of aldoximes.1103... 

The imidazo[ 1,2-b][l,2,4]triazino[5,6-6]indoles 597 were prepared by reacting 3-amino[l, 2,4]triazino[5,6-6]indole 592 with a-bromoketones 596. The structure was confirmed by the identity with the product of a reaction between isatin 599 or 2-phenylimino-3-oxoindole 600 and 1,2-diamino-4,5-diphenylimidazole 598 (82ZOR1272). Similarly, a cyclocondensation of 1,2-diamino-4-arylimidazoles with isatin and N-methylisatin was carried out (82KGS242). 

An unexpected one-pot two-step transformation of 3,4-diphenyl-l,2,5-thiadiazole 8 via the intermediate trimethylsi-lylmethylated 3,4-diphenyl-1,2,5-thiadiazolium triflate 20 gave the l-trimethylsilylmethyl-4,5-diphenylimidazole 139. The proposed reaction mechanism invokes desilylation of thiadiazolium 20 with CsF to afford the methide 138 (Scheme 21) <1999J(P1)1709>. 

As compounds exhibiting enhancing effects on CL reactions, a variety of phenols, e.g., firefly luciferin and 6-hydroxybenzothiazole derivatives [12,13], 4-iodophe-nol [14], 4-(4-hydroxyphenyl)thiazole [15], 2-(4,-hydroxy-3 -methoxy-benzyli-dene)-4-cyclopentene-l,3-dione (KIH-201) [16], and 2-(4-hydroxyphenyl)-4,5-diphenylimidazole (HDI) and 2-(4-hydroxyphenyl)-4,5-di(2-pyridyl)imidazole (HPI)[17] (Fig. 6A), and phenylboronic acid derivatives, e.g., 4-phenylylboronic acid [18], 4-iodophenylboronic acid [19], and4-[4,5-di(2-pyridyl)-l //-imidazol-2-yl]phenylboronic acid (DPPA) [20] (Fig. 6B), in the luminol/hydrogen peroxide/peroxidase system are well known. Rhodamine B and quinine are used as sensitizers in the CL-emitting reaction between cerium (IV) and thiol compounds. This CL reaction was successfully applied to the sensitive determination of various thiol drugs [21-32],... 

Hydrazinium salts, 73 567-568 2-(4-Hydrazinocarbonylphenyl)-4,5-diphenylimidazole (HCPI), chemiluminescence reagent, 5 851 Hydrazone formation, microwaves in, 76 565... 

Amino-4,5-diphenylimidazole was reacted with EMME to give imi-dazo[l,2-a]pyrimidine-6-carboxylate (1113, R = R = Ph) (51BSB69). 

Nitroso-2,5-diphenylimidazole is instantaneously and quantitatively hydrolyzed to 3-benzoyl-5-phenyloxadiazole when heated to 50—60° with dilute hydrochloric acid. Other disubstituted nitrosoimidazoles are already hydrolyzed by water [21, 22). The hydrolysis is reported to occur as follows ... 

Involvement of AModo species in electrophilic C-iodinations needs to be considered since a number of imidazoles are known to form such compounds in basic medium. Charge-transfer complexes, too, are quite well known. They seem to be of the n -type through the unshared electron pair at N-3. Equilibrium constants for their formation are known to increase regularly in line with electron-donating powers of substituents (or vice versa). Some KCT values at 20°C (L M are imidazole (200), 1-methylimidazole (333), 1,2-dimethylimidazole (1165), 4-phenylimidazole (152), and 4,5-diphenylimidazole (141) (83BSB923). The charge-transfer complexes formed between iodine and imidazole-2-thiones appear to involve the sulfur atoms (88JA2586). 

Correlations between pK,d values and the equilibrium constants for the formation of iodine complexes with imidazoles suggest that the charge transfer complexes are of the /j-type involving donation of the unshared electron pair at N-3. For examples of K and pK3 values are imidazole, 202, 6.95 1-methylimidazole, 333, 7.33 4-phenylimidazole, 152, 6.10 4,5-diphenylimidazole, 141, 5.90 (83BSB923). 

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