Nonracemic, chiral homoenolate reagents derived from (cycloalk-1-enyl)methyl carbamates and evaluation of their configurational stabilities

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Nonracemic, chiral homoenolate reagents derived from (cycloalk-1-enyl)methyl carbamates and evaluation of their configurational stabilities. / Özlügedik, M.; Kristensen, Jesper Langgaard; Wibbeling, B.; Fröhlich, R.; Hoppe, D.

In: European Journal of Organic Chemistry, No. 3, 01.01.2002, p. 414-427.

Research output: Contribution to journalJournal articleResearchpeer-review

Harvard

Özlügedik, M, Kristensen, JL, Wibbeling, B, Fröhlich, R & Hoppe, D 2002, 'Nonracemic, chiral homoenolate reagents derived from (cycloalk-1-enyl)methyl carbamates and evaluation of their configurational stabilities', European Journal of Organic Chemistry, no. 3, pp. 414-427.

APA

Özlügedik, M., Kristensen, J. L., Wibbeling, B., Fröhlich, R., & Hoppe, D. (2002). Nonracemic, chiral homoenolate reagents derived from (cycloalk-1-enyl)methyl carbamates and evaluation of their configurational stabilities. European Journal of Organic Chemistry, (3), 414-427.

Vancouver

Özlügedik M, Kristensen JL, Wibbeling B, Fröhlich R, Hoppe D. Nonracemic, chiral homoenolate reagents derived from (cycloalk-1-enyl)methyl carbamates and evaluation of their configurational stabilities. European Journal of Organic Chemistry. 2002 Jan 1;(3):414-427.

Author

Özlügedik, M. ; Kristensen, Jesper Langgaard ; Wibbeling, B. ; Fröhlich, R. ; Hoppe, D. / Nonracemic, chiral homoenolate reagents derived from (cycloalk-1-enyl)methyl carbamates and evaluation of their configurational stabilities. In: European Journal of Organic Chemistry. 2002 ; No. 3. pp. 414-427.

Bibtex

@article{a6f33244ba5648499ab8c8ef0506a2c7,
title = "Nonracemic, chiral homoenolate reagents derived from (cycloalk-1-enyl)methyl carbamates and evaluation of their configurational stabilities",
abstract = "Several (cycloalk-1-enyl)methyl N,N-diisopropylcarbamates 11 were synthesised by three different methods and their asymmetric deprotonation by butyllithium/(-)-sparteine was investigated. The ratios of epimeric ion pairs 18·4/epi-18·4 were determined by (stereospecific) trimethylsilylation, forming the products 19/ent-19. Lithiated 2-unsubstituted (cyclopent-1-enyl) methyl carbamates, such as 11a or 11h, epimerise rapidly at -78 °C and the thermodynamically controlled ratio is opposite to the kinetically achieved ratio. High configurational stability was found for the 2-methylcycloalk-1-enyl derivatives 11d, 11e and 11j. These turned out to be valuable reagents for enantioselective homoaldol reaction; er values of up to 96:4 could be achieved. X-ray crystal structure analyses with anomalous diffraction, obtained from the heavy atom containing products 22, 23b, 27d, and 27e derived from (2-methylcyclopentenyl)methyl and (2-methyl-cyclohexenyl)methyl reagents, established the (1S) configuration of the major lithium compound. Thus, the kinetically controlled deprotonation of the corresponding allyl carbamates removes the (pro-S) proton. Overall, a simple method for the enantioselective synthesis of cyclic homoaldol adducts from achiral precursors is reported.",
author = "M. {\"O}zl{\"u}gedik and Kristensen, {Jesper Langgaard} and B. Wibbeling and R. Fr{\"o}hlich and D. Hoppe",
year = "2002",
month = "1",
day = "1",
language = "English",
pages = "414--427",
journal = "European Journal of Organic Chemistry",
issn = "1434-193X",
publisher = "Wiley - V C H Verlag GmbH & Co. KGaA",
number = "3",

}

RIS

TY - JOUR

T1 - Nonracemic, chiral homoenolate reagents derived from (cycloalk-1-enyl)methyl carbamates and evaluation of their configurational stabilities

AU - Özlügedik, M.

AU - Kristensen, Jesper Langgaard

AU - Wibbeling, B.

AU - Fröhlich, R.

AU - Hoppe, D.

PY - 2002/1/1

Y1 - 2002/1/1

N2 - Several (cycloalk-1-enyl)methyl N,N-diisopropylcarbamates 11 were synthesised by three different methods and their asymmetric deprotonation by butyllithium/(-)-sparteine was investigated. The ratios of epimeric ion pairs 18·4/epi-18·4 were determined by (stereospecific) trimethylsilylation, forming the products 19/ent-19. Lithiated 2-unsubstituted (cyclopent-1-enyl) methyl carbamates, such as 11a or 11h, epimerise rapidly at -78 °C and the thermodynamically controlled ratio is opposite to the kinetically achieved ratio. High configurational stability was found for the 2-methylcycloalk-1-enyl derivatives 11d, 11e and 11j. These turned out to be valuable reagents for enantioselective homoaldol reaction; er values of up to 96:4 could be achieved. X-ray crystal structure analyses with anomalous diffraction, obtained from the heavy atom containing products 22, 23b, 27d, and 27e derived from (2-methylcyclopentenyl)methyl and (2-methyl-cyclohexenyl)methyl reagents, established the (1S) configuration of the major lithium compound. Thus, the kinetically controlled deprotonation of the corresponding allyl carbamates removes the (pro-S) proton. Overall, a simple method for the enantioselective synthesis of cyclic homoaldol adducts from achiral precursors is reported.

AB - Several (cycloalk-1-enyl)methyl N,N-diisopropylcarbamates 11 were synthesised by three different methods and their asymmetric deprotonation by butyllithium/(-)-sparteine was investigated. The ratios of epimeric ion pairs 18·4/epi-18·4 were determined by (stereospecific) trimethylsilylation, forming the products 19/ent-19. Lithiated 2-unsubstituted (cyclopent-1-enyl) methyl carbamates, such as 11a or 11h, epimerise rapidly at -78 °C and the thermodynamically controlled ratio is opposite to the kinetically achieved ratio. High configurational stability was found for the 2-methylcycloalk-1-enyl derivatives 11d, 11e and 11j. These turned out to be valuable reagents for enantioselective homoaldol reaction; er values of up to 96:4 could be achieved. X-ray crystal structure analyses with anomalous diffraction, obtained from the heavy atom containing products 22, 23b, 27d, and 27e derived from (2-methylcyclopentenyl)methyl and (2-methyl-cyclohexenyl)methyl reagents, established the (1S) configuration of the major lithium compound. Thus, the kinetically controlled deprotonation of the corresponding allyl carbamates removes the (pro-S) proton. Overall, a simple method for the enantioselective synthesis of cyclic homoaldol adducts from achiral precursors is reported.

UR - http://www.scopus.com/inward/record.url?scp=0036169729&partnerID=8YFLogxK

M3 - Journal article

AN - SCOPUS:0036169729

SP - 414

EP - 427

JO - European Journal of Organic Chemistry

JF - European Journal of Organic Chemistry

SN - 1434-193X

IS - 3

ER -

ID: 45437991