Scalable Syntheses of 4-Substituted Pyridine-Diimines.

A concise benchtop and scalable synthesis of pyridine-diimine (PDI) ligand frameworks is presented using inexpensive commercial starting materials as opposed to previous syntheses of these ligands, which have confronted long and tedious routes that employ toxic and often difficult to scale pyrophoric reagents. The streamlined synthesis is derived from the facile delivery of 4-functionalized diacetylpyridines from a Minisci reaction using pyruvic acid, silver nitrate, and persulfate. As the PDI ligand scaffold has been adopted for a range of catalytic applications, the ability to modulate the electronic properties of the ligand with facility may be useful for optimizing a variety of catalytic transformations.