AZOLES .11. SYNTHESIS OF IMIDAZOLE-2-CARBALDEHYDE AND IMIDAZOLE-5-CARBALDEHYDE DERIVATIVES OF IMIDAZO [1,2-B]ISOQNINOLINE TRANSMETALATION OF IMIDAZOL-5-YLLITHIUM COMPOUNDS

The transmetallations of 1-protected 4-bromoimidazol-5-yllithium deriv atives have been studied using DMF as the quenching reagent. 4-Bromoim idazole-2-carbaldehydes are usually the major products and not the -5- carbaldehydes as reported previously. Various attempts to prevent or i nhibit these transmetallations are described. Cyclisation of 4-bromo(a nd o)-1-(3,4-dimethoxybenzyl)imidazole-2-carbaldehyde and -(3,4-dimeth oxybenzyl)benzimidazole-2-carbaldehyde in TFA gave the corresponding i midazo- or benzimidazo-[1,2-b]isoquinoline.