All Wrapped Up – Catalyst-Containing Wax Capsules Instead of Glove Boxes

By Kevin Szkop, Symposium Coordinator for the GCI

What if you could do air-sensitive chemistry without a glove box or Schlenk line?

This is the idea behind the company XiMo, launched by Amir Hoveyda from Boston College, Richard Schrock from MIT and their co-workers.

Schrock, Hoveyda and many others work in the area of making carbon-carbon bonds.  The carbon-carbon bond is ubiquitous in nature, found in (nearly) every organic and naturally occurring molecule. The complexity of design that can be obtained from a seemingly simple chemical bond is unparalleled. The formation of carbon-carbon bonds is very important in the manufacturing of pharmaceuticals, food and natural products, agricultural chemicals, materials, and more. Notably, synthetic organic and inorganic chemists work together to design catalysts that are able to carry out this priceless transformation.

There have been many advances in this regard, especially in the field of coupling reactions and bond metathesis (the swapping of partners by a re-distribution of alkene and alkyne groups), both endeavours earning their discoverers Nobel prizes.1,2 However, a shortcoming in this field is the air- and moisture-sensitivity of the catalysts that need to be used for these transformations. The typical way of overcoming this problem is through the use of a glove box.

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Typical glove box used to protect air- and moisture-sensitive materials.

A glove box is an essential piece of laboratory equipment to the synthetic chemist. By providing an air- and moisture-free environment, sensitive chemistry can easily be performed.
While useful, glove boxes are expensive to buy and operate, require a lot of inert gas (argon or nitrogen) to maintain a clean and dry working atmosphere, and a lot of upkeep is needed to maintain their successful operation.

 

In efforts to address these issues, Amir Hoyveda from Boston College, Richard Schrock from MIT, and coworkers have launched the company XiMo3, which manufactures paraffin tablets containing air and moisture sensitive materials. Using less rigorous techniques for the exclusion of air and moisture from the reaction vessel than a glove box, the organic chemist can simply add the tablet to the desired reaction. The tablets will release their contents in the reaction solvent under mild heating conditions. Therefore, even though precautions must be taken, the overall process eliminates the need for a glove box.4

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Paraffin wax tablet

Many different factors affect the integrity of the paraffin wax tablets. The active compound must be able to dissolve in the reaction medium and release its contents under desirable conditions, it must be air- and water-stable, and the active compounds must be homogeneously dispersed within the volume of the tablet, but not on the surface. These problems have all been overcome since the company’s founding in 2005.

Some of the commercially available catalysts (shown below) are widely used in metathesis reactions for the construction of complex molecular carbon backbones.5,6,7 These reagents have been successfully incorporated into a paraffin tablet and show equivalent activity in selected reactions compared to the traditional catalyst in reactions performed under air- and moisture-free conditions.

 

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Typical metathesis catalysts embedded in paraffin wax tablets.

The company’s founders hope that this new technology will speed up research and development endeavours, particularly in the field of drug synthesis. Bypassing the need for a glovebox, the paraffin tablets will allow a wide range of organic chemists to explore the rich chemistry obtainable by these air sensitive catalysts.

 

References

  1. http://www.nobelprize.org/nobel_prizes/chemistry/laureates/2005/
  2. http://www.nobelprize.org/nobel_prizes/chemistry/laureates/2010/
  3. XiMo Technologies: http://www.ximo-inc.com/technology-updates
  4. Chemistry World News, Oct. 2016: https://www.chemistryworld.com/news/wax-pills-for-safe-and-simple-olefin-metathesis-hit-the-market/1017567.article
  5. Koh, M.-J.; Nguyen, T. T.; Zhang, H.; Schrock, R. R.; Hoveyda, A. H.Nature2016, 531,
  6. Lam, C. Zhu, K. V. Bukhryakov, P. Müller, A. H. Hoveyda, R. R. SchrockJ. Am. Chem. Soc. 2016, 138, 15774.
  7. T. Nguyen, M. J. Koh, X. Shen, F. Romiti, R. R. Schrock, A. H. HoveydaScience, 2016, 352, 569.

 

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