HIGH-YIELDING SYNTHESES OF 4(5)-SUBSTITUTED IMIDAZOLES VIA ORGANOLITHIUM INTERMEDIATES. THE UTILITY OF SULPHONAMIDE N-PROTECTION AND SILICON-CONTAINING BLOCKING GROUPS

Article abstract of DOI:10.1016/S0040-4020(01)90617-9

N-protection of imidazole as its N,N-dimethyl-sulphonamido derivative, and blocking of the 2-position with the triethylsilyl group permits regioselective 5-metallation with sec-butyl-lithium.The resulting organolithium intermediates react with a range of electrophiles and the products are easily deprotected to give the 4(5)-substituted NH-free imidazoles in good to excellent yields.Isolation of the silicon-blocked intermediate is unnecessary and, indeed, is disadvantageous to final yields, making the procedure attractively economical of time.