Azide-Alkyne Cycloaddition
Introduction
The Azide-Alkyne Cycloaddition is a type of Click Chemistry, a term coined by K. Barry Sharpless, to describe reactions that are high yielding, wide in scope, create only byproducts that can be removed without chromatography, are stereospecific, simple to perform, and can be conducted in easily removable or benign solvents. The Azide-Alkyne Cycloaddition, in particular, is a [3+2] cycloaddition between an azide and an alkyne to give a 1,2,3-triazole.
Mechanism
The mechanism of the Azide-Alkyne Cycloaddition is a concerted process that involves the simultaneous formation of two new bonds. The reaction proceeds through a six-membered transition state, with the nitrogen atoms of the azide and the carbon atoms of the alkyne aligning in a cyclic arrangement. This results in the formation of a 1,2,3-triazole ring.
Copper Catalyzed Azide-Alkyne Cycloaddition (CuAAC)
The Copper Catalyzed Azide-Alkyne Cycloaddition (CuAAC) is a variant of the Azide-Alkyne Cycloaddition that is catalyzed by copper. The CuAAC reaction is often referred to as the quintessential click reaction, due to its reliability, specificity, and biocompatibility.
Ruthenium Catalyzed Azide-Alkyne Cycloaddition (RuAAC)
The Ruthenium Catalyzed Azide-Alkyne Cycloaddition (RuAAC) is another variant of the Azide-Alkyne Cycloaddition. The RuAAC reaction is less commonly used than the CuAAC reaction, but it offers certain advantages, such as the ability to be conducted in water and at room temperature.
Applications
The Azide-Alkyne Cycloaddition has a wide range of applications in various fields, including organic chemistry, polymer chemistry, material science, and biochemistry. It is commonly used in the synthesis of 1,2,3-triazoles, which are valuable building blocks in the synthesis of pharmaceuticals, agrochemicals, and functional materials.