Isomerisations of cycloalkene- and bicycloalkene-derived achiral epoxides by enantioselective alpha-deprotonation

Enantioselective a-deprotonation-rearrangement of cis-cyclooctene oxide 1 using organolithiums in the presence of(-)-sparteine 4 or (-)-alpha-isosparteine 5 gives the (-)-alcohol 2 in good yields and ees, The use of C-2-symmetric bisoxazolines (-)-6a-d as ligands allows access to the (+)-alcohol 2....

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Published inJournal of the Chemical Society, Perkin Transactions 1 no. 14; pp. 2151 - 2161
Main Authors Hodgson, DM, Lee, GP, Marriott, RE, Thompson, AJ, Wisedale, R, Witherington, J
Format Journal Article
LanguageEnglish
Published CAMBRIDGE Royal Soc Chemistry 21.07.1998
Subjects
Chemistry
Chemistry, Organic
Physical Sciences
Science & Technology
ALCOHOLS
KETONES
ABSOLUTE-CONFIGURATION
CONVERSION
ISOMERIZATION
ENHANCEMENT
MESO-EPOXIDES
NORTRICYCLANOL
LIGAND
INDUCED REARRANGEMENTS
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Summary:Enantioselective a-deprotonation-rearrangement of cis-cyclooctene oxide 1 using organolithiums in the presence of(-)-sparteine 4 or (-)-alpha-isosparteine 5 gives the (-)-alcohol 2 in good yields and ees, The use of C-2-symmetric bisoxazolines (-)-6a-d as ligands allows access to the (+)-alcohol 2. (-)-alpha-Isosparteine 5 functions as an efficient asymmetric ligand catalyst in the rearrangement of 1., The a-deprotonation process can be extended to other cycloalkene-derived achiral epoxides 7, 9, 11, 15 and 19. Lithium amide-induced transformations of rigid bicycloalkene-derived epoxides (25, 34 and 42) are described, providing insight into the rearrangement mechanisms which operate following a-lithiation in such systems. The enantioselective a-deprotonation-rearrangement of bicycloalkene-derived epoxides (25, 29 and 42) to ketones (28, 33 and 44 respectively) is described.
ISSN:1472-7781
0300-922X
1364-5463
DOI:10.1039/a802434k