TY - JOUR

T1 - Tricarbonyl(η6-1,2-dioxobenzocyclobutene)chromium(0)

T2 - Preparation, Nucleophilic Addition Studies and Syntheses of Complex Polycyclic Systems by Dianionic Oxy-Cope Rearrangement

AU - Brands, Michael

AU - Wey, Hans G.

AU - Bruckmann, Joachim

AU - Krüger, Carl

AU - Butenschön, Holger

PY - 1996/2

Y1 - 1996/2

N2 - The tricarbonylchromium complex 3 of 1,2-dioxobenzocyclobutene (1) is easily prepared by hydrolysis of diacetal 4. Complex 3 stereoselectively undergoes both single and double nucleophilic addition reactions at the keto groups. As a consequence, addition of excess alkenyllithium to 3 gives rise to a dianionic oxy-Cope rearrangement yielding benzocyclooctenedione complexes with good diastereoselectivity. Trapping of the bis(enolate) intermediate with chlorotrimethylsilane gives bis(enolether) 23. Subsequent addition of two different alkenyllithium derivatives yields the asymmetrically substituted rearrangement product 15. To some extent, dependent on the method of hydrolysis, an intramolecular aldol addition follows the dianionic oxy-Cope rearrangement. This results in the formation of benzoanellated bicyclo[3.3.0]octane derivatives and, in the case of 1-cyclopentenyllithium as the alkenylmetal, in the tetraquinane system 19. The trans-anellation of one of the cyclopentane rings in trans-20 has been verified by an X-ray structural analysis. The highly substituted rearrangement product 21/22 is formed only in small yield; in solution the bis(enol) tautomeric form 22 is favored over diketone 21.

AB - The tricarbonylchromium complex 3 of 1,2-dioxobenzocyclobutene (1) is easily prepared by hydrolysis of diacetal 4. Complex 3 stereoselectively undergoes both single and double nucleophilic addition reactions at the keto groups. As a consequence, addition of excess alkenyllithium to 3 gives rise to a dianionic oxy-Cope rearrangement yielding benzocyclooctenedione complexes with good diastereoselectivity. Trapping of the bis(enolate) intermediate with chlorotrimethylsilane gives bis(enolether) 23. Subsequent addition of two different alkenyllithium derivatives yields the asymmetrically substituted rearrangement product 15. To some extent, dependent on the method of hydrolysis, an intramolecular aldol addition follows the dianionic oxy-Cope rearrangement. This results in the formation of benzoanellated bicyclo[3.3.0]octane derivatives and, in the case of 1-cyclopentenyllithium as the alkenylmetal, in the tetraquinane system 19. The trans-anellation of one of the cyclopentane rings in trans-20 has been verified by an X-ray structural analysis. The highly substituted rearrangement product 21/22 is formed only in small yield; in solution the bis(enol) tautomeric form 22 is favored over diketone 21.

KW - Asymmetric syntheses

KW - Chromium complexes

KW - Diones

KW - Oxy-Cope rearrangements

KW - Polycycles

UR - http://www.scopus.com/inward/record.url?scp=0000575353&partnerID=8YFLogxK

U2 - 10.1002/chem.19960020210

DO - 10.1002/chem.19960020210

M3 - Article

AN - SCOPUS:0000575353

VL - 2

SP - 182

EP - 190

JO - Chemistry - a European journal

JF - Chemistry - a European journal

SN - 0947-6539

IS - 2

ER -