Enantioselective Diels-Alder Reactions: NMR Spectroscopy of a Chiral Titanium Lewis Acid under High Pressure

✍ Scribed by Tietze, Lutz F. ;Ott, Christian ;Frey, Urban

• Book ID: 102368202
• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 398 KB
• Volume: 1996
• Category: Article
• ISSN: 0947-3440
• DOI: 10.1002/jlac.199619960110

✦ Synopsis

Abstract

^1^H‐NMR investigations of the temperature and pressure dependence of the equilibrium of the reaction of the tartaric acid derivative 7 with titanium dichloride diisopropoxide (8) to give the chiral Lewis acid 9 show that increasing pressure and temperature shift the equilibrium to the achiral Lewis acid 8. The observed decrease in enantioselectivity of the cycloaddition reaction of isoprene (3) with 3‐crotonyl‐1,3‐oxazolidin‐2‐one (4) in the presence of 7 and 8 under high pressure may therefore be attributed at least in part to the unfavorable influence of pressure on the formation of 9.