[7189-69-7] · C6H6N4O2S · N,N´-Sulfuryldiimidazole · (MW 198.23)
(reagent for the generation of imidazolylsulfonates which function as leaving groups in SN2 displacement reactions)
Physical Data: stable crystalline solid, mp 141 °C.
Preparative Method: can be prepared from the reaction of Imidazole and Sulfuryl Chloride in THF at ambient temperature.2
Purification: recrystallized from ethanol.
In general, tetrasubstituted sulfamides tend to be very unreactive. However, N,N´-sulfuryldiimidazole was demonstrated to undergo amide exchange with subsequent rearrangement (eq 1).
Primary and secondary alcohols can be converted to their imidazolylsulfonate esters via the reaction of the corresponding alkoxides (Sodium Hydride, N,N-Dimethylformamide) with N,N´-sulfuryldiimidazole. Alternatively, the alkoxides were prepared from the action of Tetra-n-butylammonium Fluoride upon the corresponding trimethylsilyl ethers. Subsequent heating with the title compound in THF at reflux afforded the desired imidazylates. The primary imidazolylsulfonates reacted with azide, fluoride, and iodide at room temperature to provide the displacement products in high yield (eq 2).
Nucleophilic displacements at the C-2 and C-3 positions of glucopyranosides proved to be equally facile when proceeding through the intermediacy of the imidazylates. Reactions at C-2 have previously been difficult or impossible to effect by other means (eqs 3 and 4).5,6
Subsequent reduction of the iodides with Tri-n-butylstannane and Azobisisobutyronitrile afforded the deoxyglycosides in good yields.
Cyclic sulfate formation followed by treatment with fluoride ion and subsequent acid hydrolysis provided the fluorinated glucose derivative (eq 5).
Alcohol-derived imidazolylsulfonates gave elimination products upon heating with Tetra-n-butylammonium Iodide in toluene at reflux (eq 6).
University of Wisconsin-Madison, WI, USA