Benzylimidazoles

Oxidative-addition of iodine also was investigated for the complex C -bzimAu]3. This complex behaves like most of the CTCs since it adds iodine at only one gold center to yield [p,-N, C -bzimAu]3l2 [59]. The X-ray structure shows that it consists of discrete trinuclear units with the three gold atoms bridged by 1 -benzylimidazolates. 

Au-C bonds, mixed metal gold-silver dimers of planar, trinuclear complexes are readily formed by mixing gold(I) carbeniates and gold(I) benzylimidazolates with silver(I) pyrazolates in stoichiometric ratios. The complexes retain the ligands associated with the metal atoms of the starting materials. 

With the sodium derivative of benzyl alcohol, dibenzyl ether was obtained in 63% yield, accompanied by 24% of A-benzylimidazole. Formation of the latter compound results from the reaction of the benzyl sulfonate with imidazol sodium in competition with the second step of the ether synthesis (b). 

These reactions correspond to the transformation of sodium benzylalcoholate with benzenesulfonic acid imidazolide, leading to A/-benzylimidazole[10] (see also references [11] and [12]) ... 

The hydrochloride salt of 4-amino-1-benzylimidazole (83 R = H) was acetylated readily by acetic anhydride to give the acetamide derivative (83 R = COCHj) (55%) (74JMC1168). Treatment with acetic-formic anhydride gave the corresponding formamide (83 R = CHO). 

Losartan potassium (1), the prototype highly selective ATi receptor antagonist (Goa and Wagstaff, 1996), was derived from the Takeda series of l-benzylimidazole-5-acetic acid derivatives, which were themselves weak angiotensin II antagonists. Losartan potassium... 

The well-known application of 2,4,6-tris(ethoxycarbonyl)-l,3,5-triazine as a diene in inverse electron demand Diels-Alder cyclizations was adapted for the synthesis of purines <1999JA5833>. The unstable, electron-rich dienophile 5-amino-l-benzylimidazole was generated in situ by decarboxylation of 5-amino-l-benzyl-4-imidazolecarboxylic acid under mildly acidic conditions (Scheme 54). Collapse of the Diels-Alder adduct by retro-Diels-Alder reaction and elimination of ethyl cyanoformate, followed by aromatization by loss of ammonia, led to the purine products. The reactions proceeded at room temperature if left for sufficient periods (e.g., 25 °C, 7 days, 50% yield) but were generally more efficient at higher temperatures (80-100 °C, 2-24 h). The inverse electron demand Diels-Alder cyclization of unsubstituted 1,3,5-triazine was also successful. This synthesis had the advantage of constructing the simple purine heterocycle directly in the presence of both protected and unprotected furanose substituents (also see Volume 8). 

The trinuclear derivatives [Au3(p-MeC6H4N = OEt)3] and [Au3(Bzim)3] (Bzim = 1-benzylimidazolate) are colorless complexes but can produce brightly colored materials by sandwiching Ag+ or Tl+ ions and forming linear-chain complexes (Figure 1.35) with interesting luminescence properties such as thermochromism [224]. They also... 

In the case of the trinuclear [ t-N1,C2-bzimAu]3 (bzim = benzylimidazolate), in addition to the extended structures that form with other metals (see Section 6.3), it also forms supramolecular networks, acting as an electron donor with small organic acids [48]. For example, it reacts with TCNQ (tetracyanoquinodimethane) giving rise to a columnar structure in which each TCNQ molecule is sandwiched between two units of the trinuclear complex in a face-to-face manner. Thus, the repetition of this pattern leads to a stacking of the type (Au3)(Au3)( t-TCNQ)(Au3)... 

The l-benzylimidazole-3-oxides 178 with DMAD gave imidazole oxalacetates (179) in high yields.148... 

The same strategy was also used in the Fackler s laboratory employing the trinuclear complex [Au(p-C2,N3-bzim)]3 (bzim = benzylimidazolate) (Fig. 12). This gold complex is able to react, for example, with acid silver... 

Methyl and methylene groups attached to an imidazole nitrogen can be metallated. In 1-benzylimidazole the extent of benzylic metallation increases with temperature and with the amount of butyllithium used. Although 1-phenylthio-methylbenzimidazole is initially lithiated at C(2) at low temperatures, when the temperature is raised, rearrangement to the rather unstable methylene-lithiated species occurs, but this anion can be trapped by electrophiles. 

The imidazo[4,5- ]triazepines 529 were synthesized in a single-pot reaction of 4-amino-l-benzylimidazole-5-carbal-dehyde 528 with 1,2-dimethylhydrazine dihydrochloride and trimethyl or triethyl orthoformate using the corresponding alcohol as the solvent (Scheme 271) <2004JME1044, 2004NN263, CHEC-III(13.14.7T1)419>. 

Polarographic data has been obtained for imidazole-4-aldehyde254 and for 1-methyl- and l-benzylimidazole-2-aldehyde.214 The polarographic behavior was found to resemble pyridine compounds more than pyrroles. 

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