- Cascade Michael addition/cycloketalization of cyclic 1,3-dicarbonyl compounds: Important role of the tethered alcohol of α,β-unsaturated carbonyl compounds on reaction rate and regioselectivity
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Reactions of α,β-unsaturated aldehydes and cyclic 1,3-dicarbonyl compounds proceed primarily by cascade Knoevenagel condensation/six-π-electron electrocyclization (K6EC, formal [3 + 3] cycloaddition), while α,β-unsaturated ketones usually react with cyclic 1,3-dicarbonyl compounds in a 1,4-addition manner. This paper discloses our findings that under acidic conditions, α,β-unsaturated carbonyl compounds (ketones and aldehydes) with a tethered alcohol react with cyclic 1,3-dicarbonyl compounds in a highly regioselective 1,4-addition fashion via in situ generation of a hypothetical α-methylene cyclic oxonium ion as the reactive Michael acceptor. Our studies uncovered the important effect of the tethered alcohol on the reaction rate and/or efficiency and some new mechanistic aspects of the cascade Michael addition/cycloketalization. Finally, the substrate scope was examined, and 43 analogues of penicipyrone and tenuipyrone were prepared in good to excellent yields.
- Yao, Hongliang,Song, Liyan,Liu, Yuan,Tong, Rongbiao
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p. 8774 - 8785
(2015/01/09)
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- Preparation of α-methylene ketones by direct methylene transfer
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Four methods for the preparation of α-methylene ketones by direct methylene transfer are presented. The procedures were optimized in order to obtain high yields.
- Rodrigues, J. Augusto R.,Siqueira-Filho, Ezequias P.,De Mancilha, Moacir,Moran, Paulo J. S.
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p. 331 - 340
(2007/10/03)
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- Baker's yeast reduction of α-methyleneketones
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The bioreduction of α-methyleneketones, R1C(=O)C(=CH2)R2 (R1 = Me, Et, Pr, iso-Bu, Ph, CH2CH2Ph; R2 = Cl, Me, Et, n-Pr, iso-Pr, n-Bu, n-C6H13, Ph, CH2Ph), was mediated by baker's yeast (Saccharomyces cerevisiae) to obtain the corresponding α-methylketones. The R1 and R2 groups had a significant influence on the rate and enantioselectivity of the reductions. The rate of C=C bond reduction was higher than that of C=O bond reduction. Only α-methyleneketones having R1 = Me yielded α-methylketones in high enantioselectivity with e.e.s of 88-99%.
- Siqueira Filho, Ezequias P.,Rodrigues, J.Augusto R.,Moran, Paulo J.S.
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p. 847 - 852
(2007/10/03)
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- 1-Hydroxymethyl-1-oxo-prostane-derivatives of the E, A and F-series
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The invention disclosed herein relates to pharmacologically active prostaglandin derivatives of the E, F, or A series having on the terminal methylene carbon of the alpha chain a substituent selected from the group consisting of: STR1 wherein R is an alkyl group and R15 is C1 -C4 alkyl, di-C1 -C4 -alkylamino, C1 -C4 alkoxy, and phenyl or phenyl substituted with one or more substituents from the group consisting of C1 -C4, OR, SR, F, or Cl wherein R is as previously defined.
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- 1-Substituted-1-oxo-prostane-derivatives of the E, A and F series
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The invention disclosed herein relates to pharmacologically active prostaglandin derivatives of the E, F, or A series having on the terminal methylene carbon of the alpha chain, a substituent selected from the group consisting of: STR1 wherein R is C1 to C6 alkyl, and phenyl or phenyl substituted with one or more substituents selected from the group consisting of C1 -C4 alkyl, OR16, SR16, F, or Cl, and R16 is C1 to C6 alkyl.
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- 15-Deoxy-16-hydroxy-17-methylene prostaglandins of the E and F series
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The invention disclosed herein relates to pharmacologically active prostaglandin derivatives of the E and F series wherein C-16 is substituted with hydroxy and methyl and a double bond is introduced between C-19 and C-20. These compounds are active as bronchodilators, anti-ulcer agents and fertility control agents.
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