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Bis(oxazoline) Pyridine Derivatives Have Been Found to be Effective Ligands for Enantioselective Transformations

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[2]. (R)-isomer of (i-Pr)-PyBOX (07-0306) is also highly effective in enantioselective transformations, e.g. Mannich reaction[3].

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.

References:

1.       Chem. Rev., 2006, 106, 3561.; Chem. Rev. 2011, 111, PR284
2.       Organometallics, 1989, 8, 846.
3.       Organometallics, 1991, 10, 500.
4.       Chem. Eur. J., 2013, 19, 10142.

Products mentioned in this blog and related products:

07-0306:  (+)-2,6-Bis[(4R)-4-(i-propyl)-2-oxazolin-2-yl]pyridine, 98+% (R)-(i-Pr)-pybox  [131864-67-0]

07-0307:  (-)-2,6-Bis[(4S)-4-(i-propyl)-2-oxazolin-2-yl]pyridine, 98+% (S)-(i-Pr)-pybox  [118949-61-4]

07-0280:  (-)-2,6-Bis[(3aS,8aR)-3a,8a-dihydro-8H-indeno[1,2-d]oxazolin-2-yl]pyridine, min. 97% Indenyl-PYBOX  [185346-09-2]

07-0303: (+)-2,6-Bis[(4R)-4-phenyl-2-oxazolin-2-yl]pyridine, 98+% (R,R)-Ph-pybox  [128249-70-7]

07-0304: (-)-2,6-Bis[(4S)-4-phenyl-2-oxazolin-2-yl]pyridine, 98+% (S,S)-Ph-pybox  [174500-20-0]

07-0390:  2,6-Bis[(4R)-benzyl-2-oxazolin-2-yl]pyridine, min. 98%  [365215-38-9]

07-0391:  2,6-Bis[(4S)-benzyl-2-oxazolin-2-yl]pyridine, min. 98%  [151670-69-8]

 Visit the below links to view related oxazoline literature on our website:

SaBox and TOX Ligands

SpinPhox-Ir Catalyst Kit