A reagent for safe and efficient diazo-transfer to primary amines: 2-azido-1,3-dimethylimidazolinium hexafluorophosphate

Abstract

Organic azides were prepared from primary amines in high yields by a metal free diazo-transfer reaction using 2-azido-1,3-dimethylimidazolinium hexafluorophosphate (ADMP), which is safe and stable crystalline. The choice of base was important in the diazo-transfer reaction. In general, 4-(N,N-dimethyl)aminopyridine (DMAP) was efficient, but a stronger base such as alkylamine or DBU was more appropriate for the reaction of nucleophilic primary amines. X-ray single crystal structural analysis and geometry optimization using density functional theory (B3LYP/6-31G**) were conducted to study the ADMP structure, and the diazo-transfer reaction mechanism was explained with the help of the results of these analyses.

Protecting‐Group‐Free One‐Pot Synthesis of Glycoconjugates Directly from Reducing Sugars

“…The reported route to glycosyl azides using DMC involves the addition of ten or more equivalents of sodium azide, and the use of D 2 O as the solvent. [10] Seeking a route that did not require a large excess of azide, we reasoned that 2-azido-1,3dimethylimidazolinium hexafluorophosphate (1, ADMP), [11,12] could be used as both activating agent for the anomeric hydroxy group and as the source of azide. ADMP was prepared by conversion of the hexafluorophosphate salt of DMC to ADMP by reaction with sodium azide, as reported by Kitamura et al [13] The reaction of ADMP with glucose 2 in a mixture of D 2 O and MeCN [14] (4:1), with an excess of Et 3 N, gave the desired b-azide 3 in 93 % yield (Scheme 1).…”

5-Azido-4-dimethylamino-1-methyl-1,2,4-triazolium Hexafluoridophosphate and Derivatives

“…A 1,4-disubstituted 1,2,4-triazolium salt bearing an azide group at the less reactive 3-position was described [10]. Crystal structures of only one 1,3-disubstituted 2-azidoimidazolium salt [11] and one 1,3-disubstituted 2-azidoimidazolinium salt [12] are known. Organic azides were occasionally converted to triazenes, essentially by reaction with N-heterocyclic carbenes.…”

Protecting‐Group‐Free One‐Pot Synthesis of Glycoconjugates Directly from Reducing Sugars

“…The reported route to glycosyl azides using DMC involves the addition of ten or more equivalents of sodium azide, and the use of D 2 O as the solvent 10. Seeking a route that did not require a large excess of azide, we reasoned that 2‐azido‐1,3‐dimethylimidazolinium hexafluorophosphate ( 1 , ADMP),11, 12 could be used as both activating agent for the anomeric hydroxy group and as the source of azide. ADMP was prepared by conversion of the hexafluorophosphate salt of DMC to ADMP by reaction with sodium azide, as reported by Kitamura et al 13.…”