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The Regioisomeric Triphenylaminoethanols –Comparison of their Efficiency in Enantioselective Catalysis
Author(s) -
Braun Manfred,
Fleischer Ralf,
Mai Brigitte,
Schneider MarcAndré,
Lachenicht Stefan
Publication year - 2004
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.200303178
Subject(s) - chemistry , diethylzinc , enantioselective synthesis , benzaldehyde , alcohol , mandelic acid , enantiomer , catalysis , yield (engineering) , titanium , organic chemistry , aldehyde , enantiomeric excess , derivative (finance) , combinatorial chemistry , medicinal chemistry , materials science , economics , financial economics , metallurgy
Abstract Both enantiomers of the novel amino alcohol ( R )‐ and ( S )‐ 2 are prepared from the corresponding enantiomer of the mandelic acid‐derived ethanediol 3 . The regioisomeric amino alcohols 1 and 2 are converted into the imines 7 and 8 , respectively. Titanium complexes 9 and 10 derived therefrom are used as catalysts for the addition of diethylzinc to benzaldehyde and yield the alcohol 11 in up to 92% ee. On the other hand, the chloro‐substituted titanium complexes 14 and 15 are able to mediate the Torgov cyclization reaction of the diketone 16 to give the estrone derivative 17 . In both reactions titanium complexes 10 and 15 derived of the novel amino alcohol 2 give higher enantioselectivities than the complexes 9 and 14 that are based on the regioisomeric amino alcohol 1 .