Here’s another neat carbon-carbon bond forming reaction (and no, we organic chemists just cannot get enough of these things). It’s from Mary Watson’s group at Delaware, and it formally takes a primary amine and turns it into a group that can couple with boronic acids. This goes through a Katritzky pyridinium salt, as shown at right, and a nickel-catalyzed coupling take that on to the product.
This is a nice connection between the various electrophiles that are known to do boronic acid couplings and the uses that these pyridiniums have been put to in the past. This appears to be the first protocol to take plain primary amino groups and use them to install their alkyl residues onto aryl rings in this way, and it appears to be compatible with a wide range of functionalities. Nitriles, alkynes, esters, amides, ketones, heterocycles, acetals, and tertiary amines all show up on both sides of the reaction, with no apparent problems. You do have to load on the BPhen ligand for the nickel, under current conditions, but (like all other metal-catalyzed couplings), this can no doubt be improved by people who are able to spend enough of their lives beating on the reaction variables. I look forward to trying this one out!