On the optical activity of α,β-unsaturated ketones

The ORD curves of several α,β-unsaturated ketones are compared with those of structurally related dienes and the similarities and differences discussed. A determination of the CD curves of a number of α,β-unsaturated ketones revealed the presence of a new very strong optically active transition close to that of the π → π^* transition. The sign of the Cotton effect associated with the π → π^* transition as determined by ORD measurements is sometimes obscured by the overlapping new transition. The CD curves of a number of α,β-unsaturated ketones were determined in a study of the effect of ring size on the sign and magnitude of the optical activity of these transitions.     

Ferrocenyl-substituted α,β-unsaturated ketones in synthesis of tetrahydropyrimidinones

Ferrocenyltetrahydropyrimidin-2-ones were prepared by reactions of linear and cyclic ,-unsaturated ketones of the ferrocene series with urea in i-PrOH in the presence of t-BuOK. The structures of the compounds prepared were studied by ¹H and ¹³C NMR and IR spectroscopy, and also by single crystal X-ray diffraction.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 11, 2004, pp. 1887–1893.Original Russian Text Copyright © 2004 by E. Klimova, Lorez, T. Klimova, Garcia, Hernandez, Ramirez.This revised version was published online in April 2005 with a corrected cover date.     

The isomerization of β,γ-to α,β-unsaturated steroidal ketones

The isomerization of 12 steroidal Δ⁵⁽⁶⁾- and Δ⁵⁽¹⁰⁾-3-ketones to the corresponding Δ⁴-3-ketones has been studied quantitatively under acid and enzymatic catalysis. Under both kinds of catalysis the Δ⁵⁽¹⁰-series reacted more slowly. At pH 1 the difference in half-time periods for the two series was a factor of 10–38, but under enzymatic catalysis the difference was magnified to a factor varying from 29 to a few hundred, the exact values being dependent on precise structural features. Recently Talalay et al.¹ reported the rates of enzymatic isomerization of several of the Δ⁵⁽¹⁰⁾-compounds which we have measured, and our values are in agreement with theirs. The mechanisms of the two types of isomerization are discussed, and two new compounds, 5-estrene-3,17-dione and the diacetate of 17α-methyl-3,5-estradiene-3,17β-diol, are reported.     

Synthesis of β-carbolines from aldehydes and ketones via the α-siloxy α,β-unsaturated esters

We report an efficient method for the synthesis of β-carbolines from α-siloxy α,β-unsaturated esters, which are accessible from a variety of aldehydes and ketones.     

Ethylene dinitrodiamine in the addition reaction to α, Β-unsaturated ketones

Summary The addition of ethylene dinitrodiamine to , -unsaturated ketones was investigated and it was established that the former is readily added to unsaturated ketones with formation of new N-nitroketones.     

Development of catalysts for the stereoselective hydrogenation of α,β-unsaturated ketones

Iridium phosphinitoxazoline complexes were found to be new efficient catalysts for the asymmetric hydrogenation of arylated α,β-unsaturated ketones. Linear as well as cyclic substrates are hydrogenated with similar success, giving selectivities of up to 99.7% ee.     

Electrochemical oxidation of allylic CH bond for α, β-unsaturated ketones without peroxide

α,β-Unsaturated ketone is one of the important building blocks of the plenty of alkaloids, spices and pharmaceutical agents. Herein, we describe a peroxide-free electrochemical strategy to realize site-selective allylic C − H oxidation for the synthesis of α,β-unsaturated ketones. This electrochemically driven oxidation exhibits a broad substrate scope. Mechanistic investigations of this reaction uncovered HOAc and H₂O as the oxygen source to achieve peroxide-free electrochemical allylic C − H oxidation.     

Enantioselective organocatalytic conjugate addition of α-nitroacetate to α,β-unsaturated ketones in water

The catalytic enantioselective conjugate addition reaction of α-nitroacetate to α,β-unsaturated ketones promoted by chiral bifunctional organocatalysts is described. The treatment of α-nitroacetate to α,β-unsaturated ketones under aqueous-phase reaction conditions afforded the corresponding Michael adducts with high enantioselectivity. The conjugate addition adducts are easily converted to chiral δ-keto nitroalkanes and δ-keto esters.     

Lipase-catalyzed kinetic resolution of α,β-unsaturated α′-acetoxy ketones

The lipase-catalyzed kinetic resolutions of the α,β-unsaturated α′-acetoxy ketones 3a,b have been investigated. Of the lipases examined, CAL-B from Candida antarctica (fraction B) has been shown to be an efficient biocatalyst, which may be used effectively in preparative scale reactions.     

Reaction of unsymmetrical α,β-unsaturated ketones with thiobarbituric acid

Carbocyclization of unsymmetrical 1,5-diarylpenta-1,4-dien-3-ones with thiobarbituric acid afforded previously unknown 7,11-diaryl-3-thioxo-2,4-diazaspiro[5.5]undecane-1,5,9-triones with high regio- and stereoselectivity. The same spiro compounds were also synthesized by three-component condensation of thiobarbituric acid with the corresponding aromatic aldehydes and 4-arylbut-3-en-2-ones.     

The Darzens condensation of α,β-unsaturated aldehydes and ketones

The one-pot Darzens condensation of α,β-unsaturated aldehydes and ketones with enolates of an α-bromo ester or ketone is described.     

Palladium-catalyzed oxidative rearrangement of diaryl alkenyl carbinols to β,β-diaryl α,β-unsaturated ketones

An unusual oxidative palladium-catalyzed rearrangement of diaryl alkenyl carbinols to β,β-diaryl α,β-unsaturated ketones is described. The geometry of the alkene product is not determined by the electronic nature of the aryl substitutents but rather is determined by substitution pattern on the aryl rings. The reaction proceeds in good yields, utilizes oxygen at atmospheric pressure as the terminal oxidant, and tolerates a variety of functional groups on the aryl rings.