PyBOX represents a very important subgroup of bis(oxazoline) (BOX) ligands for asymmetric synthesis. Often in PyBOX two enantiomeric oxazoline rings containing a bulky substituent at the 4- and/or the 5-carbon positions are bridged with the pyridine, forming a C2 symmetrical molecule.
PyBOX is a tridentate “pincer-type” ligand and able to coordinate with a wide range of metals including alkaline earth, d- and f-transition metal atoms. Upon coordination of oxazoline rings through the N atoms, two stereogenic centers are produced near the metal center. This can influence and control the enantioselective process.
Pyridine-linked bis(oxazoline) ligands were introduced by Hisao Nishiyama in 1989. He used RuCl3/(S)-(i-Pr)-PyBOX (07-0307) catalyst for asymmetric hydrosilylation of ketones. (R)-isomer of (i-Pr)-PyBOX (07-0306) is also highly effective in enantioselective transformations, e.g. Mannich reaction.
Today PyBOX ligands exist with a wide range of structural diversities. Metal complexes incorporating Phenyl [(R,R)-Ph-PyBOX (07-0303) (S,S)-Ph-PyBOX (07-0304)], benzyl [(R) 07-0390 and (S) 07-0391] and Indenyl-PYBOX (07-0280) ligands are effective enantioselective catalysts for a variety of asymmetric synthesis.
For more detailed descriptions of each catalytic process please review the corresponding technical note for each item on our website.
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