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High Asymmetric Induction in Conjugate Additions of RCu · BF 3 to Chiral Enoates. Preliminary communication
Author(s) -
Oppolzer Wolfgang,
Löher Heinz J.
Publication year - 1981
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19810640842
Subject(s) - chemistry , saponification , conjugate , asymmetric induction , enantiomer , selectivity , medicinal chemistry , stereochemistry , chiral auxiliary , organic chemistry , enantioselective synthesis , catalysis , mathematical analysis , mathematics
1,4‐Additions of PhCu · BF 3 , n ‐Bu · BF 3 and MeCu · BF 3 to the trans ‐8‐phenyl‐menthyl enoates 1 proceeded with high chiral induction. Saponification of the resulting esters 2 gave the corresponding enantiomerically pure β‐substituted alkanoic acids 3 and the recovered (−)‐8‐phenylmenthol in good overall yields. Analogous additions to the cis ‐crotonate 1 led preferentially to the acids 3 enantiomeric to those obtained from the trans ‐crotonate 1 , although with lower selectivity. A stereochemical model is proposed consistent with the observed results (Scheme 2, Table) .