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Pure Appl. Chem. Vol.
74, No. 1, pp. 57-62 (2002)
Pure and Applied Chemistry
Vol. 74, Issue 1
Arene chromium complexes with functionalized anellated rings. Selective
formation of highly substituted polycycles*
Institut für Organische Chemie, Universität
Hannover, Schneiderberg 1B, D-30167 Hannover, Germany
Abstract: Tricarbonylchromium complexes of benzocyclobutenone,
benzocyclobutenedione, and 1,3-indandione are readily prepared by hydrolysis
of the complexes of the corresponding acetals. Reduction of the benzocyclobutenone
complex gives rise to an oxy-anion-driven ring opening to the corresponding
ortho-quinodimethane intermediate, which can be trapped with dienophiles.
Addition of 1-ethoxy-1-lithioethene allows a stereoselective ring expansion
followed by an anionic ketol rearrangement with complete diastereoselectivity.
Addition of 1-lithio-1-methoxyallene gives rise to a rare anionic 1-vinylcyclobutenol-cyclohexadienol
rearrangement. Diaddition of alkenylmetal reagents at both keto groups
in benzoyclobutenedione complexes causes dianionic oxy-Cope rearrangements
to occur at 78 °C, which are followed by diastereoselective
intramolecular aldol additions. In some cases, a completely regioselective
mono hydrolysis of di(enolates) was observed. Dianionic oxy-Cope rearrangements
can also be realized with unstrained benzil derivatives giving 1,6-hexanediones
and the corresponding aldol adducts. The 1,2,3-indantrione complex is
obtained by oxidation of the 1,3-indandione complex with dimethyldioxirane
in good yield and reacts with its central ketone group in hetero DielsAlder
*Lecture presented at the 11th IUPAC International
Symposium on Organometallic Chemistry Directed Towards Organic Synthesis
(OMCOS-11), Taipei, Taiwan, 22-26 July 2001. Other presentations are
presented in this issue, pp.1-186.
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