A series of novel N-squaramidoacid ligands were prepared conveniently. Without converting to corresponding amino alcohols, these ligands could be used in asymmetric borane reduction of prochiral aromatic ketones to give secondary alcohols in good to excellent enantiomeric excesses. The results showed that N-squaramidoacids are more efficient ligands than N-sulfonyl amino acids. N-Squaryl proline was proved to be an excellent ligand in this catalytic asymmetric process.
The six multiimidazole copper(Ⅰ)complexes are utilized to mimic tyrosinase.The main product is 3,5-di-t-butylcatechol from o-hydroxylation of the substrate 2,4-di-t-butylphenol.The highest yield of catechol is up to 82.2% and selectivity 94.8% by [Cu(I)_(3b)(MeCN)_2](ClO_4)_2 and O_2 under mild conditions,which are found to be more efficient than that already reported.
Benzoin condensation promoted efficiently in three imidazolium based room tempera- ture ionic liquids [bmim]Br, [bmim]BF4 and [Bnmim]BF4 is reported for the first time. Benzoins were obtained in up to 91% yield within less than 30 min under mild conditions.
A series of tyrosinase model ligands and complexes containing polyimidazoles wereprepared. 2, 4-Di-tert-butyl-phenol was ortho-hydroxylated by the binuclear copper (?) complex[Cu2(6a)(CH3CN)2](ClO4)2 8a and molecular dioxygen under mild conditions with up to 80.4%yield, 91.4% selectivity and 92.0% conversion.
