From Deadly to Scented: Aldehydes as CO surrogates

Carbonylation reactions are one of the most investigated organic chemistry transformations nowadays. They consist in the introduction of a very simple functional group, the carbonyl group (CO), inside molecules for the synthesis of amides, esters and ketones. These compounds are crucial in the pharmaceutical and agrochemical industry. They are typically prepared by using carbon monoxide (CO) as a reagent. CO is a toxic, colorless, odorless and tasteless gas: if something goes wrong, you die before you know it!

That’s why chemists have been working on safer molecules able to release carbon monoxide (CO) in a controlled way, the so-called CO surrogates. The problem? Most existing options come with serious drawbacks: they need long synthetic routes, demand harsh conditions (like high temperatures, strong acids, or costly catalysts), and once CO release begins, it can’t be stopped. This is a clear safety risk!

To truly move the field forward, we figured the ideal surrogate shouldn’t need any synthesis at all, but instead be something you can buy off the shelf. With our background in photocatalysis, we saw an opportunity: a CO photosurrogate. Light-driven methods are not only sustainable and mild, but they also come with a unique safety feature: CO release can be controlled as easily as flicking a switch.

If you’ve followed our previous post on the HAcTive strategy, you might recall that when certain aldehydes undergo hydrogen atom transfer (HAT), they generate an acyl radical that can decarbonylate to give an alkyl radical. In our paper, we showed how this decarbonylative HAT pathway boosts both selectivity and efficiency in radical chemistry.

But then we asked ourselves: why are we wasting all that CO gas being released? Couldn’t aldehydes themselves serve as CO photosurrogates, simply by harnessing photocatalyzed HAT? That’s where it all began. Curious? Check out our paper to see how we turned this idea into a working concept!

Luna, Valè, Ana e Luca on a very hot day in the Campus.