4-phenylimidazole derivative

Kumar S, Jailer D, Patel B, LaLonde JM, DuHadaway JB, Malachowski WP, Prendergast GC, Muller AJ (2008) Structure based development of phenylimidazole-derived inhibitors of indoleamine 2, 3-dioxygenase. J Med Chem 51 4968-4977... 

Because of the structural requirements of the bielectrophile, fully aromatized heterocycles are usually not readily available by this procedure. The dithiocarbamate (159) reacted with oxalyl chloride to give the substituted thiazolidine-4,5-dione (160) (see Chapter 4.19), and the same reagent reacted with iV-alkylbenzamidine (161) at 100-140 °C to give the 1 -alkyl-2-phenylimidazole-4,5-dione (162) (see Chapter 4.08). Iminochlorides of oxalic acid also react with iV,iV-disubstituted thioureas in this case the 2-dialkylaminothiazolidine-2,4-dione bis-imides are obtained. Thiobenzamide generally forms linear adducts, but 2-thiazolines will form under suitable conditions (70TL3781). Phenyliminooxalic acid dichloride, prepared from oxalic acid, phosphorus pentachloride and aniline in benzene, likewise yielded thiazolidine derivatives on reaction with thioureas (71KGS471). 

This approach (Scheme 3) has been applied (53JCS1636) to the synthesis of 4(5)-aminoimidazole derivatives with potential antihistamine or anthelmintic properties. For example, 4(5)-amino-2-thymyloxymethylimidazole (47) was obtained from benzyl-thymyloxy acetothioimidate hydrochloride (42) (75%). Similarly, 4(5)-amino-2-phenylimidazole (48) and 4(5)-amino-2-(thiophen-3-yl)imidazole (49) were prepared (72CA19645) from benzyl-phenyl acetothioimidate hydrochloride (43) and benzyl-(thiophen-3-yl) acetothioimidate hydrochloride (44), respectively. 

A number of 2-substituted imidazoles were found to be 4(5)-alkylated by soft electrophiles. Thus, 2-phenylimidazole (112) reacts with 3-thienylmethyl bromide to give mainly 4- and 4,5-di-substituted products A-alkylation occurs only to a minor extent (Equation 2). Similarly, 2-methoxybenzyl chloride gives rise mainly to C-substituted products. Benzyl bromide, a harder electrophile, gives largely A-benzyl derivatives of (112). 

It should be noted that a similar reaction indirectly verifying the said mechanism is also found for 1,2-diamino-4-phenylimidazole 148 [125]. The only difference between the two reactions is the fact that in the latter case it is not the nitrogen atom but is the 7i-excessive carbon reaction center that participates in cyclocondensation (Scheme 4.46). Also, subsequent heteroaromatization of the dihydro derivative 150 into imidazopyridine 151 does not require amino-group elimination. 

The reaction of l-phenylimidazole with nitronium tetrafluoroborate (25°C, 30 min) produces 5-nitro-l-phenylimidazole (67NEP6609553), whereas a patent claim that mononitration of 2-phenylimidazole gives 4-nitro-2-phenylimidazole, and not the 4-nitrophenyl derivative, was an error (70GEPI953999). 

Phenylimidazole was synthesized by treatment with Raney Ni of the corresponding thiohydantoin derivative. This desulfurization was considered to take place via the tautomeric dimercaptoimidazole, as shown in eq. 13.67.143... 

Reaction of oxalyl chloride with compound 301 gives the thiazolidine-4,5-dione 302 (Scheme 146), and the same reagent with A-alkylbenzamidine 303 at 100-140G affords the l-alkyl-2-phenylimidazole-4,5-dione 304 (Scheme 147). Imi-nochlorides of oxalic acid react with N,N-disubstituted thioureas to give the 2-dialkylaminothiazolidine-4,5-dione bis-imides 305. Phenyliminooxalic acid dichloride likewise yielded thiazolidine derivatives on reaction with thioureas <1971KGS471>. 

Diphenyl-4-nitrosoimidazole is oxidized by amyl nitrate to the corresponding 4-nitro derivative [592], An unusual reaction is observed when 4,5-diphenylim-idazole and 2-bromo-4,5-diphenylimidazole are boiled with amyl nitrite. Instead of nitrosation the substrate undergoes nitration with the formation of 2-nitro-4,5-di-phenylimidazole [593] (Scheme 115). 

Methyl /3-hydroxypropionimidates (12) (prepared from ethylene cyanohydrin, methanol, and HO) condense with aminoacetaldehyde dimethylacetal (13) to yield an amidine hydrochloride (14) which undergoes ring closure to an imidazole.87 Applications of this reaction have been used in the synthesis of 2-phenylimidazole and its 4-alkyl derivatives,88 some new 2-mercaptoimidazoles,89 and isohistamine .90 Isohistamine [2-(2 -aminoethyl)imidazole], originally reported in error by Jones,01 was prepared in 50% yield by an adaptation of the method of Ellinger and Goldberg92 and proved by NMR spectroscopy to be the authentic compound. The compound prepared... 

Imidazole reacts very slowly with singlet oxygen to form the imida-zolidone (86)42S through an elimination reaction involving proton loss and cleavage of the oxygen-oxygen bond of the transannular peroxide (87). On the other hand, 4-phenylimidazole forms a hydantoin derivative (88) and V-benzoyl-V -methoxycarbonylurea (89). This... 

Oxidation of Schiff bases of the monoamide 8 derived from diamino-maleonitrile gives 4-cyanoimidazole-5-carboxamides (Eq. 4). A new synthesis of 2-formyl-4-methyl-l-phenylimidazole 3-oxide (10) involves the fluoride-ion-promoted cyclization of the trimethylsilyl ether of JV-dichloro-acetyl-A-phenylaminopropanone oxime (9). ... 

Values of molar Kerr constants and dipole moments of nitrogen azoles and their complexes with phenols have been obtained. " These complexes are formed by an intermolecular hydrogen bond between the pyridine-type nitrogen of the azole and the phenolic proton. " The use of dipole moments in conformational studies has shown that A-aryl- and C-aryl- and A-furyl- and C-furyl imidazoles (and benzimidazoles) are nonplanar, but l-(a-furyl)-4,5-diphenylimidazoles do have a planar bicyclic fragment. The dipole moments and conformations of azolides (A-acylazoles) have been studied. In the 1-arylimidazoles the dipole is toward the aryl group. In 4,5-di-t-butylimidazole the molecule is essentially planar, but the C-4—C-5 bond is slightly stretched. Among other imidazole derivatives which have been studied by X-ray are histidine hydrochloride, 4-acetyl-amino - 2 - bromo - 5 - isopropyl -1 - methylimidazole, 4- acetyl - 5 - methyl - 2 -phenylimidazole, and imidazole-4-acetic acid hydrochloride. 

The oxidation reactions of 2,4,5-triphenylimidazole (lophine) have received considerable attention. With chromic acid it gives benzamide and benzanilide, but even more interest has centred on its involvement in the phenomenon of chemiluminescence. Some of this material has been discussed earlier (Sections 4.06.3.6, 4.07.1.2.1 and 4.07.1.2.3). The oxidative decomposition of lophine in the presence of air is accompanied by the emission of light, and it is the excited singlet state of the diaroylarylamidine (12 Scheme 2) which is the light emitter. The radical (46) derived from oxidation of lophine with aqueous ferricyanide and ethanolic KOH forms a hydroperoxide with hydrogen peroxide with consequent luminescence. When 2,4,5-tri- and 1,2,4,5-tetra-phenylimidazoles are oxidized in dilute methanol solution in the presence of methylene blue, the dibenzoylbenzamidine is also formed under circumstances in which hydroperoxides cannot be intermediates (B-76MI40701). 

The electrophilic carbene, 4H-imidazolylidene (63), has been prepared by photodecomposition of 4-diazo-4H-imidazole (64). Reaction with cyclohexane affords the C-H insertion product, 4(5)-cyclohexylimidazole (65), whereas reaction with benzene yields 4(5)-phenylimidazole (66). Analogous addition of 4H-imidazolylid-ene to derivatives of benzene is influenced by the presence and nature of the substituents. 

To obtain monoalkyl derivatives, sodium salts of A-aryl- [71 JCS(B) 1648] and A-acylaminoazoles are alkylated, then the acyl group is removed. 1-Alkylamino derivatives of 6-chlorobenzimidazole (73CC41) and 2-amino-4-phenylimidazole (67CB3418) were thus obtained [Eq. (77)]. 

In 4,5-di-t-butylimidazole the molecule is essentially planar, but the C-4—C-5 bond is slightly stretched. Among other imidazole derivatives which have been studied by X-ray are histidine hydrochloride, 4-acetyl-amino-2-bromo-5-isopropyl-l-methylimidazole, 4-acetyl-5-methyl-2-phenylimidazole, and imidazole-4-acetic acid hydrochloride. ... 

The aromatic ring system has been prepared both from quinoxaline intermediates and from 1-phenylimidazoles. Reaction of the 2-chloroquinoxalines 1 with aminoacetaldehyde dimethylacetal followed by acid treatment of the resultant aminoacetals gave imidazo[l,2-ajquinoxaline (2) and its 4-phenyl derivative (3). Compound 3 was the... 

The kinetically best characterized system for which a bimolecular reductive elimination has been proposed is a neutral hydrido porphyrin derivative of Ru(III) [4]. Cyclic voltammetry and double potential step chronoamperometry afford data that are more consistent with a second order than with a first order decay for the 17-electron RuH(OEP)(L) (OEP = octaethylporphyrin L = THE, 1 -tert-bytyl-S-phenylimidazole) complexes in THF as solvent. The second order dependence of the rate constant and the independence on the parent 18-electron anion concentration exclude the proton transfer mechanism. The possibility of a disproportionation mechanism (which would afford the same second order dependence, see section 6.5.2), however, has not been considered, nor were studies in solvents other than THF carried out. In the light of the gathered information, the mechanism shown in Scheme 17 was proposed. 

A novel synthesis of imidazoles was reported by Junjappa and co-workers [84JCS(CC)430], in which the reaction of enaminones 316 (R = H) with nitrosyl chloride gives the nitrosoenaminones 317, which are cyclodehy-drated to the -H imdazoles 318 in high yields. Scheme 89 (path a). The transformation can be done in one step with some of the enaminones under more forcing conditions (path b). Also, 1-phenylimidazoles 319 can be prepared by heating the enaminones 316 (R = H) with nitrosobenzene in sealed tubes (path c). The method was successfully extended to the synthesis of 2,2-disubstituted 2-H imidazoles 320 for enaminones 316 (R H) (87S547). Tetrahydrobenzimidazoles are prepared similarly from the cyclodehydration of a-nitroso enaminones derived from 1,3-cyclohexanediones (80JHC1723). 

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