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Precatalyst Promises Improved Cross-coupling

June 18, 2015
Scaffold structure leads to less-expensive and highly active reactions.

Chemists at Yale University, New Haven, Conn., have developed a versatile highly active precatalyst scaffold for palladium-catalyzed reactions. It promises to have wide-ranging utility for many cross-coupling and related reactions involving monoligated palladium, the researchers believe. The system is more active than commercially available precatalysts and is compatible with a range of N-heterocyclic carbene and phosphine ligands. It creates a better chemical infrastructure for catalysis, reducing the amount of palladium needed and, thus, cost, they add.


Figure 1. These vials contain a range of new chemical catalysts based on palladium. Source: Yale University

“We have developed an improved system that is less prone to deactivation. It should make the preparation of many industrially relevant compounds more economical and sustainable and may lead to new methods to prepare important compounds,” says Nilay Hazari, an associate professor of chemistry at Yale and coauthor of a recent article on the process in the journal ACS Catalysis.

The new precatalyst can serve as a drop-in replacement for current catalysts. “Our results indicate that our catalyst system is, in fact, superior to a number of existing commercially available catalysts. In addition, our system is compatible with two very important classes of ligands, which is a unique feature for this set of palladium precatalysts,” notes Patrick Melvin, a graduate student in chemistry at Yale and lead author of the article.

Work currently underway aims to expand the number of reactions the catalyst system can successfully perform. It already has shown utility for close to 40 different reactions. “We believe we have a truly versatile catalyst. …[that] will be useful in developing new chemical reactions that require a palladium catalyst,” says Melvin. “Our goal is to find challenging or interesting reactions that our catalyst might be able to improve on. This will be an ongoing objective in our lab for the foreseeable future,” he notes.

One of the key challenges remaining is compatibility. “We know that our system is excellent for a number of reactions with varying conditions. However, palladium catalysis is a very wide field, with a plethora of reaction conditions to choose from. Moving forward, we would like to ensure that our system is compatible with different reactions as well as the conditions that are favorable for those reactions,” explains Melvin.

The team has been in contact with industry scientists “who are very interested in our research;” collaboration with them is ongoing, he concludes.

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