ELECTROPHILIC AROMATIC SUBSTITUTION .37. CARBODESILYLATION OF (TRIMETHYLSILYL)IMIDAZOLES AND (TRIMETHYLSILYL)PYRAZOLES

被引:24
作者
EFFENBERGER, F
ROOS, M
AHMAD, R
KREBS, A
机构
关键词
IMIDAZOLES; (TRIMETHYLSILYL)IMIDAZOLES; CARBODESILYLATION OF; PYRAZOLES; CARBODESILYLATION;
D O I
10.1002/cber.19911240727
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
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.
引用
收藏
页码:1639 / 1650
页数:12
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