Details
| Original language | English |
|---|---|
| Pages (from-to) | 2519-2527 |
| Number of pages | 9 |
| Journal | European Journal of Organic Chemistry |
| Issue number | 13 |
| Publication status | Published - 6 Jun 2001 |
Abstract
Lithiated heterocycles and phenyllithium were tested as alkenyllithium components in the dianionic oxy-Cope rearrangement taking place upon their addition to (η6-benzocyclobutenedione) tricarbonylchromium (1). It was found that, with 5-lithio-2,3-dihydrofuran, the rearrangement and subsequent intramolecular aldol addition takes place diastereoselectively. Treatment of 1 with phenyllithium, 2-lithio-N-methylpyrrole, 2-lithiofuran, or 2-lithiothiophene, however, resulted only in the formation of single adducts and proximally or distally ring-opened diadducts, presumably because of the activation energy required to negate the aromatic character of two added anions. When, therefore, the monovinyl adduct rac-19 was used as starting material, addition both of 2-lithiofuran and of 2-lithiothiophene resulted in the desired dianionic oxy-Cope rearrangements, followed by intramolecular aldol addition. Remarkably, the intramolecular aldol addition takes place with complete regioselectivity, meaning that the bis(enolate) hydrolysis is regioselective. This is explained by a chelate stabilization of one enolate moiety in preference to the other one, hydrolysis of which is thus highly favored.
Keywords
- Chromium, Dianionic oxy-Cope rearrangement, Heterocycles, Lithiation, Rearrangements
ASJC Scopus subject areas
- Chemistry(all)
- Physical and Theoretical Chemistry
- Chemistry(all)
- Organic Chemistry
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In: European Journal of Organic Chemistry, No. 13, 06.06.2001, p. 2519-2527.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Lithiated heterocycles as substrates for dianionic oxy-Cope rearrangements - Chelation accounts for regioselective enolate hydrolysis
AU - Voigt, Beate
AU - Wartchow, Rudolf
AU - Butenschön, Holger
PY - 2001/6/6
Y1 - 2001/6/6
N2 - Lithiated heterocycles and phenyllithium were tested as alkenyllithium components in the dianionic oxy-Cope rearrangement taking place upon their addition to (η6-benzocyclobutenedione) tricarbonylchromium (1). It was found that, with 5-lithio-2,3-dihydrofuran, the rearrangement and subsequent intramolecular aldol addition takes place diastereoselectively. Treatment of 1 with phenyllithium, 2-lithio-N-methylpyrrole, 2-lithiofuran, or 2-lithiothiophene, however, resulted only in the formation of single adducts and proximally or distally ring-opened diadducts, presumably because of the activation energy required to negate the aromatic character of two added anions. When, therefore, the monovinyl adduct rac-19 was used as starting material, addition both of 2-lithiofuran and of 2-lithiothiophene resulted in the desired dianionic oxy-Cope rearrangements, followed by intramolecular aldol addition. Remarkably, the intramolecular aldol addition takes place with complete regioselectivity, meaning that the bis(enolate) hydrolysis is regioselective. This is explained by a chelate stabilization of one enolate moiety in preference to the other one, hydrolysis of which is thus highly favored.
AB - Lithiated heterocycles and phenyllithium were tested as alkenyllithium components in the dianionic oxy-Cope rearrangement taking place upon their addition to (η6-benzocyclobutenedione) tricarbonylchromium (1). It was found that, with 5-lithio-2,3-dihydrofuran, the rearrangement and subsequent intramolecular aldol addition takes place diastereoselectively. Treatment of 1 with phenyllithium, 2-lithio-N-methylpyrrole, 2-lithiofuran, or 2-lithiothiophene, however, resulted only in the formation of single adducts and proximally or distally ring-opened diadducts, presumably because of the activation energy required to negate the aromatic character of two added anions. When, therefore, the monovinyl adduct rac-19 was used as starting material, addition both of 2-lithiofuran and of 2-lithiothiophene resulted in the desired dianionic oxy-Cope rearrangements, followed by intramolecular aldol addition. Remarkably, the intramolecular aldol addition takes place with complete regioselectivity, meaning that the bis(enolate) hydrolysis is regioselective. This is explained by a chelate stabilization of one enolate moiety in preference to the other one, hydrolysis of which is thus highly favored.
KW - Chromium
KW - Dianionic oxy-Cope rearrangement
KW - Heterocycles
KW - Lithiation
KW - Rearrangements
UR - http://www.scopus.com/inward/record.url?scp=0034953001&partnerID=8YFLogxK
U2 - 10.1002/1099-0690(200107)2001:13<2519::AID-EJOC2519>3.0.CO;2-B
DO - 10.1002/1099-0690(200107)2001:13<2519::AID-EJOC2519>3.0.CO;2-B
M3 - Article
AN - SCOPUS:0034953001
SP - 2519
EP - 2527
JO - European Journal of Organic Chemistry
JF - European Journal of Organic Chemistry
SN - 1434-193X
IS - 13
ER -