Efficient Synthesis of a C2‐Symmetric 2,2'‐Bipyridine‐α,α'‐1‐t‐butyl‐diol Ligand by Stereoselective Double Hydrogen Transfer to a 2,2'‐Bipyridine‐diketone

An efficient and practical method was developed for the synthesis of C2‐symmetric 2,2'‐bipyridine‐α,α’‐1‐t‐butyl‐diol ligands. The disclosed synthesis involves the Ullmann homocoupling of a keto bromo‐pyridine under NiCl2/Zn/PPh3 conditions, followed by the stereoselective double hydrogen transfer to the obtained 2,2'‐bipyridine‐diketone using RuII Noyori–Ikariya catalysts. This approach allowed the successful synthesis of 2,2'‐bipyridine‐α,α'‐1‐t‐butyl‐diol, i.e (S,S)‐Bolm's ligand, with a quantitative yield and an excellent stereoselectivity (ee > 99.5%, de > 99.5%), with an overall yield of 69% from easily accessible starting materials.