Metallation and metal-halogen exchange reactions of imidazoles

Abstract

1-Ethoxymethyl-2-phenylthioimidazol-5-yl-lithium (4) has been prepared by metallation of 1-ethoxymethyl-2-phenylthiomidazole with n-butyl-lithium in ether or tetrahydrofuran and allowed to react with carbon dioxide, 4-methylbenzaldehyde, dimethyl disulphide, diphenyl disulphide, and the disulphide prepared from 2-mercaptoacetaldehyde diethyl acetal. 1-Ethoxymethyl-5-methylthio-2-phenylthioimidazol-4-yl-lithium (18) has been prepared via bromination of 1-ethoxymethyl-5-methylthio-2-phenylthioimidazole (9) and exchange of the bromine atom in the product (15) with n-butyl lithium. It has been treated with dimethyl disulphide, NN-dimethylformamide, and carbon dioxide, to give the corresponding sulphide (14), aldehyde (16), and acid (17), respectively. 2,5(4)-Bis(phenylthio)imidazole (23) prepared by treatment of its 1-ethoxymethyl derivative (10) with acid, iodinated in the 4-position to yield 4(5)-iodo-2,5(4)-bis(phenylthio) imidazole (24).