Enantioselective Diels‐Alder Reactions: NMR Spectroscopy of a Chiral Titanium Lewis Acid under High Pressure
- 1 January 1996
- journal article
- research article
- Published by Wiley in European Journal of Organic Chemistry
- Vol. 1996 (1) , 63-67
- https://doi.org/10.1002/jlac.199619960110
Abstract
1H‐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.Keywords
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