Phosphorus beats palladium in connecting nitrogen rings
An entirely metal-free reaction goes where no traditional cross-coupling has gone before – to link pyridines
Ask any chemists what element they think of when they hear ‘cross-coupling’ and the answer will most likely be palladium. But it turns out that ‘unfashionable’ phosphorus outclasses palladium when it comes to connecting pyridines.
Although nitrogen heterocycles are part of many drugs, such as the cancer medication imatinib, they often prove challenging for palladium. They can bind to the catalyst, killing its reactivity. Even just making the corresponding cross coupling precursors – like halogenated pyridines or pyridine boronic acids – is notoriously difficult.