Group 13 sulfides imidazole

Below is part of the structure of ribonuclease surrounding one of the catalytic amino acids Hisl2. There are seven amino acids in this sequence. Every one is different and every one has a functionalized side chain. This is part of a run of ten amino acids between Phe8 and Alai 9. This strip of peptide has six different functional groups (two acids, one each of amide, guanidine, imidazole, sulfide, and alcohol) available for chemical reactions. Only the histidine is actually used. 

In the presence of base, 2-isocyanoalkanenilriles [70] react with alcohols, thiols or hydrogen sulfide to form imidazoles which have oxygen or sulfur groups in the 4(5) position. The reactions appear to proceed via the 4ff-imidazoles, which rearrange to the Iff-isomers [71]. There are similarities to the synthesis of 4-methoxyimidazole made, in 60% yield, by refluxing the Af-cyanomethylimino ester of formic acid with sodium methoxide in methanol [72]. 

Imidazole- and benzimidazole-2-thiols usually exist largely as the thione tautomers. The thiol (thione) group is susceptible to alkylation (especially in alkaline media), and can be oxidized to sulfide, disulfide and sulfonic acid. This oxidation can often be carried out quite selectively by careful choice of oxidizing agent. The sulfur function can be removed with nitric acid, iron(III) chloride, hydrogen peroxide or, most commonly, Raney nickel. Alkyl- and arylthio groups can be oxidized to sulfoxide or sulfone. 

Under the same basic conditions /ra . -l-acetoxymethyl-1-methyl-2-tosylcyclopropane generated an a-sulfonyl anion, which attacked the ester group intramolecularly and afforded 2,5-dimethyl-l-tosyl-3-oxabicyclo[3.1.0]hexan-2-ol (22) in 50% yield.Stereoselective synthesis with a chiral cyclopropyl sulfoxide was experienced when ( )-4-tolylsulfinylcyclopropane was reacted first with butyllithium and then with methyl benzoate and gave 1-benzoyl-1-[(5)-4-tolylsulfinyl]cyclopropane (23a) in 62% yield. A useful reaction took place when 2-(hy-droxymethyl)cyclopropyl phenyl sulfide was treated first with an excess of butyllithium and then with dimethylformamide and gave 2-hydroxy-l-phenylsulfanyl-3-oxabicyclo[3.1.0]hexane (24), a lactol which has been used to carry out various useful synthetic transformations. Another useful reaction occurred when cyclopropyl phenyl sulfones were treated with butyllithium followed by an acyl imidazole to give acyl cyclopropanes in decent yield. 

An iron porphyrin bearing (5)-naphthylpropionic amide groups has been synthesized by Zhou et al. [113]. With 10% of catalyst, methyl phenyl sulfide was oxidized in 94% yield, but with only 8% ee. The addition of imidazole increased the optical purity to 15%, but the yield of the reaction decreased to 79%. 

N,N -carbonyl bis(4-methoxy metanilic acid) disodium salt sal disodica de N,N -carbonil bis(acido 4-metoximetanriico) carbonyl bromide bromuro de carbonilo carbonyl chloride cloruro de carbonilo carbonyl cyanide cianuro de carbonilo carbonyl fluoride fluoruro de carbonilo carbonyl group gmpo carbonilo carbonyl sulfide sulfuro de carbonilo l,l -carbonyldi-imidazole l,l -carbonildi-imidazol... 

Davis introduced some complimentary strategies for the synthesis of functional ionic liquids, by the inclusion of functional group (FG) to the cationic skeleton, in his review (Davis, 2004). The called "task-specific ionic liquids" have been synthesized, for example, by N-alkylation of alkyl halides covalently linked to FG with appropriate Lewis bases (e.g., imidazole, amine, phosphine, and sulfide Scheme 2a), accompanied by the anion metathesis to realize ionic liquids. One of other strategies is to use Michael reaction of alkyl vinyl ketones linked to FG with tertiary cations, as in Scheme 2b (Wasserscheid et al., 2003). It is noteworthy that this facile one-pot reaction dispenses with the need for a further anion metathesis step and are free from haUde-containing by-product. 

Scheme 2. Schematic synthetic routes of functional ionic liquids by (a) N-alkylation reaction (Davis, 2004) and (b) Michael addition reaction (Wasserscheid et al, 2003) to form ionic liquids of functional cations, and (c) the addition of acidic group to form ionic liquids of functional anion. A blank sphere represents a Lewis base such as imidazole, amine, phosphine, and sulfide, while a sphere with a plus sign represents the corresponding cation.

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