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Bicyclic and Tricyclic Compounds with β‐Amino Alcohol Groups as Chiral Ligands in the Enantioselective Reaction of Diethylzinc with Aldehydes
Author(s) -
Aurich Hans Günter,
Biesemeier Frank,
Geiger Michael,
Harms Klaus
Publication year - 1997
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.199719970222
Subject(s) - chemistry , diethylzinc , bicyclic molecule , diastereomer , enantioselective synthesis , benzaldehyde , cycloaddition , intramolecular force , alcohol , medicinal chemistry , organic chemistry , stereochemistry , catalysis
Reduction of the enantiomerically pure allyloxy esters 9 or ent ‐ 9 with DIBAH afforded the corresponding aldehydes which were treated in situ with chiral or achiral hydroxylamines 8 to give nitrones 10 . These underwent a spontaneous intramolecular 1,3‐dipolar cycloaddition, affording the bicyclic compounds 11 and 12 , respectively. In an analogous manner, a mixture of the tricyclic compounds 14 and 15 was prepared. Treatment of compound 16 with cyclohexene oxide afforded a mixture of diastereomers 17 and 18 . Diastereomers 14 and 15 as well as 17 and 18 could be separated by chromatography. X‐ray analyses of compounds 11Ff , 17 , and 11Af · HCl were performed. The bicyclic and tricyclic compounds were used as chiral ligands in the reaction of diethylzinc with aldehydes 19 , in particular with benzaldehyde ( 19a ). Using bicyclic compounds with a tertiary β‐hydroxyalkyl substitutent at the N atom as ligands, ee's in the range of 78 to 95% were found. Whereas for the best ligands 11Ae and Af the enantioselectivity in the reaction of 4‐tolualdehyde was only slightly decreased, with the aliphatic aldehydes 19c and d distinctly lower enantioselectivities were determined.