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Enantioselective Diels‐Alder Reactions: NMR Spectroscopy of a Chiral Titanium Lewis Acid under High Pressure
Author(s) -
Tietze Lutz F.,
Ott Christian,
Frey Urban
Publication year - 1996
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199619960110
Subject(s) - chemistry , isoprene , lewis acids and bases , enantioselective synthesis , diels–alder reaction , titanium , tartaric acid , cycloaddition , chiral lewis acid , derivative (finance) , nuclear magnetic resonance spectroscopy , lewis acid catalysis , organic chemistry , medicinal chemistry , polymer chemistry , catalysis , polymer , economics , financial economics , copolymer , citric acid
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 .
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