New Ligands: Hydroxyoxazolinyl[2.2]paracyclophanes in Asymmetric Catalysis

Significance

Synthesis and use of pseudo-geminal, pseudo-ortho and ortho hydroxyoxazolinyl[2.2]paracyclophanes as N,O-ligands is described. The pseudo-geminal compounds were accessed by directed bromination followed by lithiation and B(OMe)₃ quench. Oxidation with H₂O₂ gave the desired ligands 1a and 1b. The pseudo-ortho ligand was accessed in a similar manner, except conversion into the benzyl ethers, separation, and subsequent deprotection was necessary to give 2a and 2b. The ortho ligand was prepared as previously described by the same authors ( J. Org. Chem. 2006, 71, 4609-4618).