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DBU-Catalyzed Deconjugation of 7-Substituted 3,4-Didehydro-2-oxepanones. Deuterium Incorporation, Significance of the Imine Double Bond, and Application to the Synthesis of a Key Pharmacophore
journal contribution
posted on 1998-01-01, 00:00 authored by Duraiswamy A. Jeyaraj, Kamal K. Kapoor, Veejendra K. Yadav, Harsh M. Gauniyal, Masood Parvez7-Substituted 3,4-Didehydro-2-oxepanones are conveniently
deconjugated to the 4,5-didehydro
derivatives by DBU. The isomerization of 7-benzyl-substituted
2-oxepanones proceeds to the extent
of 90% over the initial 3 h; the concentration falls gradually
thereafter to achieve, in 25 h, a 3:2
equilibrium in favor of deconjugation. Such an equilibrium does
not exist for the 7-methyl and the
7-(2-phenethyl) derivatives. The significance of the imine double
bond in DBU has been explored.
The isomerization in CDCl3 causes deuterium
incorporation at positions 3 and 5 of the 2-oxepanones
examined and at position 6 of DBU. The mechanistic rationales for
these deuterium incorporations
are advanced. The transformation of
7-benzyl-3,4-didehydro-2-oxepanone into a
bicyclo[3.3.0]
skeleton that is present in a diverse class of biologically active
natural products is described as a
possible potential use of the present deconjugation
methodology.