SYNTHESIS OF 1-(DIMETHYLSULFAMOYL)-2-IMIDAZOLECARBOXALDEHYDE AND 1-(DIMETHYLSULFAMOYL)-5-IMIDAZOLECARBOXALDEHYDE - REARRANGEMENT OF 1-(DIMETHYLSULFAMOYL)-5-IMIDAZOLE-CARBOXALDEHYDE TO THE 4-CARBOXALDEHYDE

Lithiation of 1-(dimethylsulfamoyl)imidazole by n-butyllithium, followed by substitution with dimethylformamide provided 1-(dimethylsulfamoyl)-2-imidazolecarboxaldehyde in 19% yield. When 1-(dimethylsulfamoyl)-2-(tert-butyldimethylsilyl)imidazole was lithiated by sec-hutyllithium, followed by methyl formate, there was obtained 1-(dimethylsulfamoyl)-2-(tert-butyldimethylsilyl)-5-imidazolecarboxaldehyde (57%). Removal of the silyl group by acetic acid yielded 1-(dimethylsulfamoyl)-5-imidazolecarboxaldehyde (11, 96%) as a gum. Isomerization of 11 took place slowly at room temperature (10 days), or faster in tetrahydrofuran solution containing triethylamine (2 hours) to form crystalline 1-(dimethylsulfamoyl)-4-imidazolecarboxaldehyde (12) in 68% yield. Proton and carbon-13 nmr spectra were analyzed to determine the structure of the isomers. However, only X-ray,crystallography established the structure of 1-(dimethylsulfamoyl)-4-imidazolecarboxaldehyde unequivocally. A mechanism for the isomerization of 11 to 12 is proposed.