Chiral hydrogenation from Bayer

Bayer AG has commercialised a new chiral hydrogenation technology to meet the demand for chiral advanced intermediates and APIs with one or more stereo-centres. The technology allows Bayer to produce chiral hydrogenation catalysts including the R and S version of Bayer's proprietary ligand Cl-MeO-BIPHEP, formally known as (R) and (S)-5,5'-dichloro-6,6'-dimethoxy-2,2'-bis(diphenylphosphino)–1,1'-biphenyl.

Cl-MeO-BIPHEP forms organmetallic complexes with the transition metals ruthenium and rhodium. The ruthenium complex is an especially versatile catalyst for the efficient enantioselective hydrogenation (ee often greater than 99%) of CO and CC double-bonded substrates.

To promote Cl-MeO-BIPHEP, Bayer has entered into an agreement with Strem Chemicals to market the ligand in research quantities. Strem, based in Newburyport, MA, US, is a leading manufacturer and marketer of r&d chemicals, and already supplies the R and S versions of Cl-MeO-BIPHEP.

Bayer's new synthesis allows the introduction of a wide spectrum of substituents (R-groups) in place of the phenyl group on the phosphorus. 'This allows us to fine-tune the catalyst more efficiently than was possible before. Previously, the racemic separation took place after the R group was attached. That required working out a separate resolution for each R group,' said Rudolph Hanko, head of Bayer's fine chemical business unit.