Base-induced cyclization of .alpha.-chloro .beta.,.gamma.-unsaturated ketones : facile synthesis of tri- and tetrasubstituted 2-cyclopenten-1-ones
摘要:
Base-induced cyclization of fully substituted alpha-chloro beta,gamma-unsaturated ketones results in substituted cyclopentenones. Potassium tert-butoxide, lithium diisopropylamide, sodium hydroxide, and ammonium hydroxide can be used as the base for this process. In the case of ammonium hydroxide, it is proposed that initial formation of an enamine is followed by an intramolecular S(N)2' reaction of the enamine carbon. For all other bases, the reaction most likely proceeds through a ketone enolate. Application of this novel cyclization has been extended to the synthesis of several 2,3-disubstituted, 2,3,5-trisubstituted, and 2,3,5-tetrasubstituted 2-cyclopenten-1-ones.
ketones are generated in moderate yields (50–60%) from allene or a mono-, di- or tri-substitutedallenic hydrocarbon, n alkyl halide and sodium tetracarbonylferrate. The first step is the formation of a complex anion which results from transfer of the alkyl group on a coordinated CO, then of the acyl ligand thus formed on the allenic sp carbon. Protonation with acetic acid yields a hydroxy-η4-trimethylenemethane
The present invention aims to provide a compound having a PDE inhibitory action and useful as a medicament for the prophylaxis or treatment of schizophrenia and the like.
A compound represented by the formula (1
x
):
wherein each symbol is as described in the DESCRIPTION, or the formula (1):
W
1
—W
2
(1)
wherein each symbol is as described in the DESCRIPTION,
or a salt thereof.
Spectroscopic studies. Part II. Steric conformations of some αβ-unsaturated ketones
作者:F. H. Cottee、B. P. Straughan、C. J. Timmons、W. F. Forbes、R. Shilton
DOI:10.1039/j29670001146
日期:——
ketones have been examined, and three main trends emerge as criteria to distinguish the two conformations. By use of these criteria some labile αβ-unsaturated ketones have been assigned conformations which are believed to predominate at room temperature, although for a number of the ketones the actual conformation is probably non-planar.
Decomposition of α-diazo-ketones: the oxiren–oxocarbene equilibrium
作者:S. A. Matlin、P. G. Sammes
DOI:10.1039/p19720002623
日期:——
A sensitive chemical test for the participation of oxirens in the decomposition of diazo-ketones has been developed, based on the subsequent rearrangement of oxocarbenes to αβ-unsaturated ketones. In this way oxiren participation has been demonstrated in the thermal and photochemicaldecomposition of a variety of diazo-ketones, including 3-diazoheptan-4-one, 1-diazo-3-phenylpropan-2-one, and 2,2-d
Convergent synthesis of methylenomycin B via selenium-assisted intramolecular S N 2? cyclization
作者:Jacob Mathew
DOI:10.1039/c39900001264
日期:——
A highly convergent and efficient synthesis of methylenomycinB has been achieved by the reaction of the lithium enolate of 4-chloro-4,5-dimethyl-5-hexen-3-one with phenylselenenyl bromide followed by selenoxide elimination.