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Syntheses of Enantiomerically Pure Cyclopent‐2‐ene‐1‐carboxylic Acid and (Cyclopent‐2‐enyl)acetic Acid by Enantioselective Palladium‐Catalyzed Allylic Alkylations − Synthesis of Enantiomerically Pure (−)‐Chaulmoogric Acid
Author(s) -
Seemann Matthias,
Schöller Markus,
Kudis Steffen,
Helmchen Günter
Publication year - 2003
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200200700
Subject(s) - chemistry , enantioselective synthesis , acetic acid , allylic rearrangement , catalysis , palladium , tsuji–trost reaction , alkylation , carboxylic acid , organic chemistry , stereochemistry , medicinal chemistry
Asymmetric Pd‐catalyzed allylic alkylations of dimethyl malonate and diethyl 2‐acetoxymalonate with 3‐chlorocyclopentene, using phosphanyloxazolines 1 and ent ‐ 1 as chiral ligands, gave products (−)‐ 2 and (+)‐ 3b with 95 and 99.5% ee , respectively. Oxidative degradation of (+)‐ 3b furnished (+)‐( R )‐cyclopent‐2‐ene‐1‐carboxylic acid [(+)‐ 4 ] with > 99% ee . Alkylation product (−)‐ 2 was transformed into enantiomerically pure (−)‐( R )‐(cyclopent‐2‐enyl)acetic acid [(−)‐ 5 ] by three simple steps. Availability of (−)‐ 5 enabled the first synthesis of enantiomerically pure (−)‐chaulmoogric acid [(−)‐ 9 ] in three steps. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
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