“Click” and Olefin Metathesis Chemistry in Water at Room Temperature Enabled by Biodegradable Micelles

Abstract

The two laboratory reactions focus on teaching several concepts associated with green chemistry. Each uses a commercial, nontoxic, and biodegradable surfactant, TPGS-750-M, to promote organic reactions within the lipophilic cores of nanoscale micelles in water. These experiments are based on work by K. Barry Sharpless (an azide–alkyne “click” reaction) and Robert Grubbs (an olefin cross-metathesis reaction); both are suitable for an undergraduate organic laboratory. The copper-catalyzed azide–alkyne [3+2] cycloaddition of benzyl azide and 4-tolylacetylene is very rapid: the triazole product is readily isolated by filtration and is characterized by thin-layer chromatography and melting point analysis. The ruthenium-catalyzed olefin cross-metathesis reaction of benzyl acrylate with 1-hexene is readily monitored by thin-layer chromatography and gas chromatography. The metathesis experiment comparatively evaluates the efficacy of a TPGS-750-M/water medium relative to a traditional reaction performed in dichloromethane (a common solvent used for olefin metathesis).

Transitioning organic synthesis from organic solvents to water. What's your E Factor?

“…This was the very first item on our agenda when developing such micellar catalysis, since reaction mixtures that foam or create intractable emulsions, regardless of the payoff downstream, are usually undesirable. Fortunately, the properties of these designer surfactants are such that their use and handling are straightforward; indeed, they are applicable to not only research purposes, but can also be utilized as undergraduate lab experiments, 80 and may be even amenable to high school classrooms where the equipment available is likely to be minimal.…”

Micellar promoted multi-component synthesis of 1,2,3-triazoles in water at room temperature

“…To the best of our knowledge the use of micellar environments has been rarely investigated for the synthesis of triazoles and never for the direct three component synthesis but always directly using organic azides. 35,36 The multicomponent synthesis of triazoles consists of two consecutive steps: (i) the in situ formation of the organic azide between sodium azide and the organic bromide and (ii) the click reaction between the organic azide and the alkyne mediated by the Cu(I) catalyst. The most suitable surfactant for the direct reaction should favor both synthetic steps and ensure good solubilization and close contact between the three reagents and the catalyst.…”

Tailor‐Made Polydiacetylene Micelles for the Catalysis of 1,3‐Dipolar Cycloadditions in Water

“…As opposed to previously reported procedures, in which a reductant such as sodium ascorbate was added to trigger Cu(II) to Cu(I) reduction, [17] we initially selected more straightforward conditions by exploiting the intrinsic one-electron transition from Cu(II) to Cu (I) observed in the course of the homo-coupling of terminal alkynes. This process, known as the Glaser-Eglinton-Hay coupling, [18] affords dimeric alkynes together with reduced copper(I).…”