133228-20-3Relevant academic research and scientific papers
Carbodesilylation of (Trimethylsilyl)imidazoles and -pyrazoles
Effenberger, Franz,Roos, Michael,Ahmad, Roshan,Krebs, Andreas
, p. 1639 - 1650 (2007/10/02)
The preparation of the 1-methyl(trimethylsilyl) (TMS)-substituted imidazoles 3a, 4a, 8, 9, and 11a by silylation of the corresponding metallated imidazoles is described.Carbodesilylation of 3 with aldehydes or carboxylic halogenides occurs selectively in 2-position.In the presence of a strong base (CsF) the reactivity against carbon electrophiles correlates well with the stability of the imidazolyl anions; regioselective carbodesilylation in 2-, 5-, or 4-position of the twofold TMS-substituted imidazoles 3a and 9 therefore is possible, which allows the synthesis of a great variety of hydroxyalkyl-substituted imidazoles and of acylimidazoles.By using the dimethylsulfamoyl substituent as an N-protecting group, the N-unsubstituted 5-benzoylimidazole (26) as well as the comparable 5-benzoyl-pyrazole (30b) and 5-(hydroxyphenylmethyl)pyrazole (30a) are accessible. Key Words : Imidazoles, (trimethylsilyl)-, carbodesilylation of / Pyrazoles, (trimethylsilyl)-, carbodesilylation of / Carbodesilylation
2-Protecting Groups for 5-Lithiation in the Synthesis of Imidazoles
Ngochindo, Raphael I.
, p. 1645 - 1648 (2007/10/02)
Various substituents have been examined as possible 2-protecting groups against organolithium reagents in the syntheses of imidazoles on the basis of the ease of decarboxylation of imidazole-2-carboxylic acids and cleavage of the C(2)-Si bond.The tertiary
