A discovery by organic chemists at UCLA may one day put catalytic converter thieves out of business. In the new study, they used the abundant and inexpensive phosphorus as a catalyst for chemical reactions that normally require precious metals such as platinum. Platinum is one of the metals targeted by auto parts theft, which converts chemicals in car exhaust into less harmful forms. However, this advancement is likely to become more useful in the pharmaceutical industry and could one day help lower the prices of some drugs.

The new research nature, It uses light-reactive molecules known as photocatalysts that react with inexpensive phosphorus compounds to bond nitrogen-containing compounds (often found in pharmaceuticals) to carbon-carbon double bonds. This type of reaction, called hydroamination, is an effective way to create more complex structures.

“Carbon-nitrogen bonds are one of the most important types of bonds for drug discovery and manufacturing. Almost all pharmaceuticals contain nitrogen, but fixing that nitrogen into molecules is difficult, so we used noble transition metal catalysts,” said Abigail Doyle, a professor of chemistry at the University of California, Los Angeles, and corresponding author of the paper.

Transition metals are shiny, conductive metals such as gold, silver, copper, iridium, platinum, and palladium. Under the right conditions, it readily reacts with many other elements, accelerating chemical reactions. Therefore, they have become essential industrial catalysts.

“These metals are used in catalytic converters in car engines and in the manufacture of a wide variety of materials, from parts for denim jeans to pharmaceuticals,” Doyle said. “But they can be very expensive to use, so there’s a lot of interest in finding cheaper transition metals to replace them, such as copper, nickel, or iron, or in finding catalysts from other blocks of the periodic table that are abundant and can react in the same way as the metals.”

Phosphorus is an essential element for life. Therefore, phosphorus compounds are very common in nature and widely used in organic chemistry.

“Chemists have developed all sorts of named reactions using phosphorus compounds, including examples where phosphine acts as a catalyst,” Doyle said.

Phosphine is a molecule containing a phosphorus atom bonded to three carbon atoms. “But we have discovered a new mode of reactivity for phosphorus that mimics the mode that transition metals like palladium and iridium commonly do in catalysis,” Doyle said.

Doyle’s lab’s discovery that light could be used to convert phosphine into something that acts as a rarer and more expensive catalyst was a serendipitous result of experimenting with ways to form carbon-nitrogen bonds.

“We were surprised to see high reactivity in a product that was completely different from what we expected. It was definitely a puzzle trying to understand what was going on,” said first author and PhD student Flora Huang. Although it wasn’t originally designed to work this way, the research team eventually determined that the phosphorus needed to act like a metal in the reaction.

This reaction proceeds via a short-lived, highly reactive form of phosphorus. This form can react with carbon-carbon double bonds through a pathway much like the way metal catalysts activate these double bonds. Although phosphines mimic the behavior of metal catalysts, they also operate by fundamentally different rules.

The main difference is that phosphines are initiated in a state where reactions can occur that involve the transfer of both one and two electrons, whereas transition metal catalysts most commonly involve the transfer of two electrons. This allows the hydroamination reaction to follow a unique pathway, allowing for the use of a wider variety of nitrogen-containing compounds.

Doyle’s team hopes these similarities and differences in reactivity will inspire new strategies using phosphorus-based catalysts to engineer chemical reactions.

“We’re excited that we’re trying to understand how far we can take this chemistry,” Huang said. “We hope this opens the door to more versatile ways to produce pharmaceutical compounds and other value-added chemicals.”

Meanwhile, car owners can hope that the discovery will eventually be applied to catalytic converters, which will become less attractive to thieves.

In addition to Doyle and Huang, the authors of the new study also include UCLA doctoral student Alexander Martens, a Ph.D. from Princeton University. Cassandra Cedillo. This study was funded by the National Institutes of Health.