Synthesis of 1‐(dimethylsulfamoyl)‐2‐ and 5‐imidazolecarboxaldehydes. Rearrangement of 1‐(dimethylsulfamoyl)‐5‐imidazole‐carboxaldehyde to the 4‐carboxaldehyde

Abstract

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‐butyllithium, followed by methyl formate, there was obtained 1‐(dimethylsulfamoyl)‐2‐(tert‐butyldimethylsilyl)‐5‐imidazolecarbox‐aldehyde (57%). Removal of the silyl group by acetic acid yielded 1‐(dimethylsulfamoyl)‐5‐imidazolecarbxaldehyde (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‐(dimethylsul‐famoyl)‐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.

Bi-imidazole nucleosides obtained by ring opening of etheno and substituted etheno derivatives of adenosine

“…The 13 C chemical shifts of C-2, C-4 and C-5 in 2b correlate well with the values observed for 2a and the differences in shifts between the carbons C-2Љ, C-4Љ and C-5Љ are easily explained by the effects of the formyl group at C-5Љ. The 13 C chemical shifts observed for C-2Љ, C-4Љ and C-5Љ are close to those reported by Kim et al 12 for 4(5)-formylimidazole and do not agree with the data reported by Aulaskari et al 13 ‡ Note: For simplicity, the explicit numbering of the atoms of 2b-2d (as depicted in Scheme 1) in the unsymmetrically substituted imidazole moieties is used throughout the text without taking into account the other possible tautomeric form.…”

Intramolecular Diels−Alder Reactions of 4-Vinylimidazoles

“…Interestingly, the DMAS-moiety appears to have migrated to the other imidazole nitrogen (N3 in 16 ). There are reports in the literature of the migration of DMAS groups on imidazoles, and it has been assumed that this is a result of the relief of steric crowding, leading to the thermodynamically most stable isomer . A similar explanation can be forwarded in this instance, since migration of the DMAS moiety would relieve steric crowding between the CO 2 Et moiety and the DMAS group .…”

Efficient Synthesis of Tris(4-imidazolyl)methanol Derivatives

“…The doubly protected carbinol 2 can be efficiently prepared in one-pot from readily available sulfonamide 1 (one step, 91% from imidazole) by adapting the regioselective lithiation method of Ngochindo and Chadwick (Scheme ) . Thus, a THF solution of 1 was treated sequentially with n -BuLi (1.05 equiv, −78 °C), t -BuMe 2 SiCl (1.1 equiv, −78 to 20 °C), n -BuLi (1.1 equiv, −78 °C), and finally diethyl carbonate (0.30 equiv, −78 to 20 °C).…”