The reductive coupling reaction of 1,4-bis(3-acetyl-5-
tert-butyl-2-methoxyphenyl)butane
3 was carried out using TiCl
4-Zn in pyridine followed by a McMurry coupling reaction to afford the compounds
anti and
syn 1,2-dimethyl[2.4]MCP-1-ene
4. Bromination of
4 with BTMA-Br
3 in dry CH
2Cl
2 afforded the interesting compound 1,2-bis-(bromomethyl)-5,15-di-
tert-butyl-8,18-dimethoxy[2.4]MCP-1-ene
6 and consecutive debromination with Zn and AcOH in CH
2Cl
2 solution afforded the stable solid 5,15-di-
tert-butyl-8,18-dimethoxy-1,2-dimethylene[2.4]MCP
7 in 89% yield. Compound
7 was conveniently employed in a Diels–Alder reaction with dimethyl acetylenedicarboxylate (DMAD) to provide 2-(3′,6′-dihydrobenzo)-5,15-di-
tert-butyl-8,18-dimethoxy[2.4]MCP-4′,5′-dimethylcarboxylate
8 in good yield. Diels–Alder adduct
8 was converted into a novel and inherently chiral areno-bridged compound [2.4]MCP
9 by aromatization. The chirality of the two conformers was characterized by circular dichroism (CD) spectra of the separated enantiomer which are perfect mirror images of each other.
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