Imidazoles metallation

Der Austausch von Alkalimetall-, Silber- oder Quecksilber-Atomen gegen Kohlenstoff-Reste wurde bereits im Rahmen der N-Alkylierung von Imidazolen abgehandelt, da die Imidazol-Metall-Verbindungen meistens nicht isoliert, sondern in situ mit dem Alkylierungsmittel weiter umgesetzt werden. Deshalb wird hier nur der Austausch des Trimethylsilyl-Restes von 1-Tri-methylsilyl-imidazolen besprochen. 

Proton acids at neutral azoles basicity of imidazoles and benzimidazoles Proton acids at imidazole anions acidity of imidazoles Metal ions... 

A review on the metaiation and metal-h ogen exchange reactions of imidazole appeared in 1985. Generally, A -protected imidazoles metalate at the 2-position 1,2-disubstituted imidazoles usually met-alate at the 5-position, unless sterically hindered. Even 2,5-dilithiation of imidazoles has been achieved. 1-Substituted 1,3,4-triazoles can be metalated at the S-position and added to carbonyls in good yield. Oxazoles are easily lithiated at the 2-position, but the resultant anion readily fragments. l-(Phenylthiomethyl)benzimidazole can be lithiated at the 2-position at low temperature (Scheme 21), but higher temperatures afford rearrangement products. ... 

This method of imidazolylzinc chloride synthesis has also found application in the synthesis of a sulfonyl chloride to be used in the preparation of some potential factor Xa inhibitors [17]. Thus, following imidazole metalation and quenching with ZnCl2, a chemoselective coupling reaction occurred to provide 16. Treatment with sulfur dioxide provided the sulfinic acid, which upon treatment with thionyl chloride, provided the requisite sulfonyl chloride 17. 

Imidazoles, metallation of and metal-halogen exchange in 85H(23)417. Imidazoles, synthesis from cyanides 84T1093. 

Fig. 3.3 The single crystal X-ray structures of zeohtic imidazolate metal-oxide frameworks (MOFs). In each row, the net is shown as a stick diagram (left) and as a tiling center). The largest cage in each MOF is shown with ZnN tetrahedra in blue (right). H atoms are omitted for clarity ...

We now have succeeded in synthesizing the first cyclam (17) bearing an appended imidazole that acts as an ideal axial donor for effective imidazole metal tt-interaction. Our synthetic procedure is simple and versatile, serving also for pyridyl [10] and phenol-appended cyclams [4]. 

Fig. 16 Analogy between an imidazolium salt (A) and a cationic imidazole metal complex (B).

Buist, G., Hamerton, L, and Barton, J. M., Comparative kinetic analyses for epoxy resins cured with imidazole-metal complexes,/ Mater. Chem., 4, 1793, 1994. 

The frequent presence of an imidazole-co-ordinated residue in an axial position, coupled with the suggestions that metal-imidazole bond rupture might play an important role in biological processes of coenzyme B12 and the cytochrome c system, indicates that a detailed characterization of the structure and dynamics of the imidazole-metal bond in such porphyrin complexes could have significant biological implications. La Mar and Walker present some preliminary data on the exchange of iV-methylimidazole (WMIm) on the bis-adduct of A MIm with [Fe(tpp)Cl] in CDCI3, and Kolski and Plane describe temperature-jump studies on the reaction between imidazole and the iron(m) derivative of ethylenediamine-substituted protoporphyrin IX in water. 

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). 

Despite the weak basicity of isoxazoles, complexes of the parent methyl and phenyl derivatives with numerous metal ions such as copper, zinc, cobalt, etc. have been described (79AHC(25) 147). Many transition metal cations form complexes with Imidazoles the coordination number is four to six (70AHC(12)103). The chemistry of pyrazole complexes has been especially well studied and coordination compounds are known with thlazoles and 1,2,4-triazoles. Tetrazole anions also form good ligands for heavy metals (77AHC(21)323). 

Azoles can form stable compounds in which metallic and metalloid atoms are linked to nitrogen. For example, pyrazoles and imidazoles Af-substituted by B, Si, P and Hg groups are made in this way. Imidazoles with a free NH group can be Af-trimethylsilylated and Af-cyanated (with cyanogen bromide). Imidazoles of low basicity can be Af-nitrated. 

Imidazole, 4-alkyl-synthesis, 5, 482 Imidazole, 5-alkyl-synthesis, 5, 481 Imidazole, N-alkyl-metallation, 5, 415-416 reactions, 5, 449-450 synthesis, 5, 387 Imidazole, 1 -alkyl-5-amino-synthesis, 5, 462... 

The structure of the diamagnetic, cherry-red vitamin B12 is shown in Fig. 26.6 and it can be seen that the coordination sphere of the cobalt has many similarities with that of iron in haem (see Fig. 25.7). In both cases the metal is coordinated to 4 nitrogen atoms of an unsaturated macrocycle (in this case part of a corrin ring which is less symmetrical and not so unsaturated as the porphyrin in haem) with an imidazole nitrogen in the fifth position. A major... 

B. Non-Metal and Non-Transition Metal Organometallic Complexes of Imidazoles. 120... 

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