Metal‐Free Fast Azidation by Using Tetrabutylammonium Azide: Effective Synthesis of Alkyl Azides and Well‐Defined Azido‐End Polymethacrylates

Abstract

An effective method to synthesize azido‐end polymethacrylates from tetrabutylammonium azide (BNN3) in a nonpolar solvent (toluene) was developed. Several low‐mass alkyl halides were reacted with BNN3 in toluene as model reactions and the rate constants of these reactions were determined, to confirm fast BNN3 azidation for tertiary and secondary halides. The end‐group transformation of halide‐end polymethacrylates was effective and nearly quantitative. Notably, the combination of organocatalyzed living (or reversible deactivation) radical polymerization and BNN3 azidation enabled the metal‐free synthesis of azido‐end polymethacrylates, including single‐azido‐end and multi‐azido‐end functional homopolymers and block copolymers. The rapid and quantitative reaction without the requirement for a large excess of BNN3, metal‐free and polar‐solvent‐free nature, and broad polymer scope are attractive features of this azidation.

Tetrabutylammonium Azide

“…An alternative method, using TBAN3 in a non-polar solvent (toluene) has been developed, allowing nearly quantitative azidation of halide-end polymethacrylates with no large excess of azide (eq 22). 19 PMMA X (24) Schmidt Reaction. The Schmidt reaction, which enables N-insertive synthesis of secondary amides from ketones, typically uses NaN3 under acidic conditions to generate hazardous hydrazoic acid (HN3) in situ.…”

Azide Ionic Liquids for Safe, Green, and Highly‐Efficient Azidation Reactions to Produce Azide Polymers

“…Recently, a variety of new azidation reagents have been developed, such as azido‐trimethylsilane, [12] diphenyl azidophosphate, [13] and Zhdankin reagent, [14] all of which have been demonstrated efficient toward small‐molecule compounds. Unfortunately, only very few studies have been reported on the preparation of azide polymers in a NaN 3 ‐free manner, which, however, either involved even more risky azide‐containing reagents, [15] or still required the usage of large amounts of organic solvents [16] . Meanwhile, since ionic liquids (ILs) have been widely used as green solvents in macromolecular reactions in recent years owing to their nonvolatility, chemical stability, and high solubility, [17] researchers have also explored the possibility of application of ILs in the synthesis of azide polymers.…”

“…Unfortunately, only very few studies have been reported on the preparation of azide polymers in a NaN 3free manner, which, however, either involved even more risky azide-containing reagents, [15] or still required the usage of large amounts of organic solvents. [16] Meanwhile, since ionic liquids (ILs) have been widely used as green solvents in macromolecular reactions in recent years owing to their nonvolatility, chemical stability, and high solubility, [17] researchers have also explored the possibility of application of ILs in the synthesis of azide polymers. However, in these cases, ILs were only used as catalysts or co-solvents, and a large excess of NaN 3 and high reaction temperatures were still mandatory.…”

Recent development in halogen-bonding-catalyzed living radical polymerization

“…Tetrabutylammonium azide (BNN 3 ) was also used instead of NaN 3 . 91 Different from NaN 3 , BNN 3 led to the substitution even in non-polar solvents. This feature enabled the post-azidation of fluorinated (super-hydrophobic) polymer-I in nonpolar solvents, which are otherwise insoluble in polar solvents.…”