5228-76-2Relevant academic research and scientific papers
Synthesis of 2-Substituted Imidazoles and Benzimidazoles and of 3-Substituted Pyrazoles by Lithiation of N-(Dialkylamino)methyl Heterocycles
Katritzky, Alan R.,Rewcastle, Gordon W.,Fan, Wei-Qiang
, p. 5685 - 5689 (2007/10/02)
The lithiation of N-(dialkylamino)methyl (aminal) derivatives of imidazole, benzimidazole, and pyrazole (themselves readily available from parent heterocycles, formaldehyde, and a secondary amine) occurs smoothly at 2-, 2-, and 5-positions, respectively, upon treatment with n-butyllithium in ether or tetrahydrofuran.Reaction with electrophiles, and subsequent facile acid-catalyzed hydrolysis of the protecting group, provides 2-substituted imidazoles, 2-substituted benzimidazoles, and 3(5)-substituted pyrazoles in good overall yields.
An Easily Introduced and Removed Protecting Group for Imidazole Nitrogen: A Convenient Route to 2-Substituted Imidazoles
Curtis, N.J.,Brown, R.S.
, p. 4038 - 4040 (2007/10/02)
Orthoamides (3-5) prepared from imidazoles and triethyl or trimethyl orthoformate are rapidly metalated at -40 deg C in THF or ether to give the corresponding 2-lithio anion which reacts with a variety of electrophiles.The dialkoxymethyl protecting group is readily hydrolyzed under neutral or acidic conditions at room temperature, giving the 2-substituted 1H-imidazole 1 (R = H, X = COOH, n-C4H9, COCH3, CHOHC6H5, C(CH3)OH-2-pyridyl,9-hydroxyfluorenyl, 1-hydroxycyclohex-2-enyl, C(OH)(C6H5)2; R = CH3, R' = H, X = CHO) and the tris(2-imidazolyl)phosphines (R = H, CH3, CH(CH3)2).A mechanism for the deprotection of 3 is proposed.
