Just Click It: New Chemical Reactions for Cosmetic Applications

In the past decade, the chemistry community has seen the resurgence of several classical chemical reactions that once lay dormant in the depths of outdated organic chemistry textbooks. Well-established since the late 19th century, these reactions were largely ignored as synthetic chemists devoted their time to the development of new synthetic methodologies to keep up with the flourishing field of natural product synthesis. Recently, a resurgence in interest surrounding these classic reactions has led to amazing discoveries in chemical biology, polymer chemistry and materials science.¹ Commonly referred to as “click chemistry,” a term coined by Sharpless in 2001,2 these reactions are characterized by their robust and rapid production of highly pure products. While a daunting number of options are available in the synthetic chemist’s toolbox, click reactions are particularly useful for the cosmetic chemist as they can be performed in benign solvents, including water; they tolerate the presence of a variety of functional groups; they produce products in exceptionally high yields; and they require minimal purification.² Starting materials are “spring-loaded” to react quickly and selectively with each other to produce single products (see Figure 1). Click reactions are widely popular in academia and are actively being exploited in drug discovery, polymer synthesis, materials science and chemical biology, but their use in cosmetic chemistry remains largely unexploited as the industry remains slow to assimilate new synthetic innovations.