Novel binuclear chiral zirconium catalysts used in enantioselective strecker reactions

✍ Scribed by Shū Kobayashi; Haruro Ishitani

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 109 KB
• Volume: 12
• Category: Article
• ISSN: 0899-0042
• DOI: 10.1002/(sici)1520-636x(2000)12:5/6<540::aid-chir42>3.0.co;2-p

✦ Synopsis

A novel binuclear chiral zirconium catalyst was successfully used in enantioselective Strecker reactions. The catalyst was readily prepared from zirconium t-butoxide (Zr(OtBu)4), (R)-6,6'-dibromo-1, 1'-bi-2-naphthol ((R)-6-Br-BINOL), and (R)-3,3'-dibromo-1, 1'-bi-2-naphthol ((R)-3-Br-BINOL) to form unique binuclear structure. It was revealed that a combination of (R)-6-Br-BINOL and (R)-3-Br-BINOL was essential in these asymmetric reactions and that much lower selectivities were obtained by using other combinations. Two-component (an imine and hydrogen cyanide (HCN)) and three-component (an aldehyde, an amine, and HCN) Strecker reactions proceeded smoothly in the presence of a catalytic amount of the chiral zirconium catalyst to afford the corresponding alpha-amino nitrile derivatives in high yields with high enantioselectivities.