Enantioselective Reduction of Electrophilic CC Bonds with sodium tetrahydroborate and ‘semicorrin’ cobalt catalysts

✍ Scribed by Marian Misun; Andreas Pfaltz

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: German
• Weight: 907 KB
• Volume: 79
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19960790404

✦ Synopsis

Abstract

‘Semicorrin’ cobalt complexes, prepared in situ from cobalt(II) chloride and the corresponding ligands, are efficient catalysts for the enantioselective reduction of electrophilic CC bonds with NaBH~4~. The best selectivities (> 90% ee) are achieved with α,β‐unsaturated carboxamides and carboxylates. Analogous α,β‐unsaturated nitriles, sulfones, and phosphonates afford enantiomeric excesses of 50–70%. Interestingly, in the reduction of α,β‐unsaturated sulfones, the highest enantioselectivities were obtained with unsymmetrical ‘semicorrins’, whereas in all other cases C~2~‐symmetric ‘semicorrins’ proved to be superior.