scispace - formally typeset
Search or ask a question

Showing papers on "Enone published in 1993"


Journal ArticleDOI
TL;DR: Crambines A (7) (eight steps, 22%). B (45d) (8 steps, 19%), C1 (98) (seven steps, 21%), and C2 (9a) (7 steps, 27%) have been synthesized expediently and stereospecifically by a biomimetic route from methyl acetoacetate as mentioned in this paper.
Abstract: Crambines A (7) (eight steps, 22%). B (45d) (eight steps, 19%), C1 (98) (seven steps, 21%), and C2 (9a) (seven steps, 27%) have been synthesized expediently and stereospecifically by a biomimetic route from methyl acetoacetate. Aminodihydropyrimidines 39 and 40 are formed efficiently from enone ester 36 by a two-step procedure involving addition of O-methylisourea to give methoxydihydropyrimidine 37 followed by displacement of the methoxy group of 37 with ammonia. Hydrogenolysis of 40a and 40d afford crambines C2 and C1, respectively. Mesylation of the alcohol of 39a or 40a followed by Et 3 N-catalyzed cyclization and hydrogenolysis affords crambine A (7)

210 citations


Journal ArticleDOI
TL;DR: In this article, the structures and energy properties of Diels-Alder reactions between cyclopentadiene and ethylene, isoprene and methyl vinyl ketone were investigated.
Abstract: Ab initio molecular orbital calculations have been used to investigate the structures and energetics for the reactants and transition states of Diels-Alder reactions between cyclopentadiene and ethylene, isoprene, cyclopentadiene, acrylonitrile, and methyl vinyl ketone (MVK). Geometry optimizations were performed with both RHF/3-21G and RHF/6-31G * calculations, and the energies were computed to the MP3/6-1G * //6-31G * level in each case. Calculations the vibrational frequencies permitted computation of the enthalpies and entropies of activation

180 citations





Journal ArticleDOI
TL;DR: A series of 2'-substituted chalcone derivatives has been found to show potent inhibition of the production of IL-1 beta from human peripheral blood monocytes stimulated with lipopolysaccharide, suggesting a degree of selectivity which would not be expected for simple, nonspecific alkylating agents.
Abstract: A series of 2'-substituted chalcone derivatives has been found to show potent inhibition of the production of IL-1 beta from human peripheral blood monocytes stimulated with lipopolysaccharide (LPS), with IC50 values in the 0.2-5.0-microM range. Some members of the series have also shown inhibition of septic shock induced in mice by injection of LPS, although with low potency. Qualitative structure-activity relationships have shown that the enone is required for activity, which may be mediated by conjugate addition of a biological nucleophile to the chalcone. Electron-poor aromatic rings beta to the ketone give enhanced potency. Although electronic effects in the other ring (directly attached to the ketone) are minimal, this ring must possess an ortho substituent for good activity without cytotoxicity, suggesting a degree of selectivity which would not be expected for simple, nonspecific alkylating agents.

86 citations




Journal ArticleDOI
TL;DR: In this paper, the Pauson-Khand reaction was used for the cocyclization of alkynes, alkenes and carbon monoxide in the presence of a stoichiometric amount of molybdenium hexacarbonyl and excess of dimethylsulfoxide.

68 citations




Journal ArticleDOI
TL;DR: The first Michael addition reactions of aminocarbene complexes to α,β-unsaturated carbonyl compounds were reported in this paper, where it was shown that the formation of the 1,4addition product is not reversible and that the initial 1, 4addition is thus kinetically controlled.
Abstract: The first Michael addition reactions of the anions of aminocarbene complexes to α,β-unsaturated carbonyl compounds are reported. Unlike their corresponding amide enolates, these anions give exclusive 1,4-addition to a number of enones. For chiral complex 27, it was shown that the formation of the 1,4-addition product is not reversible and that the initial 1,4-addition is thus kinetically controlled. The anions of aminocarbene complexes are much more effective in this regard than the anions of alkoxycarbene complexes. It was demonstrated that aminocarbene complexes can serve as synthons for amides in Michael additions since the metal can be liberated from the Michael adducts to give amide products by oxidation with either DMSO or dimethyldioxirane

Journal ArticleDOI
TL;DR: A very general preparative method for homoallyllithiums consists of reductive lithiation of homophilyl phenyl sulfides by lithium 4,4'-di-tert-butylbiphenylide as mentioned in this paper.
Abstract: A very general preparative method for homoallyllithiums consists of reductive lithiation of homoallyl phenyl sulfides by lithium 4,4'-di-tert-butylbiphenylide. The sulfides can be prepared by a variety of methods including (1) the triethylamine-catalyzed addition of thiophenol to a conjugated enal or enone followed by a Wittig or Peterson olefination, (2) the reaction of a silyl enol ether with a diphenyl dithioacetal catalyzed by stannic chloride, followed by a Peterson olefination, or (3) the treatment of the lithio derivatives of phenyl thioethers or thioacetals or the corresponding cuprates with allyl halides

Journal ArticleDOI
TL;DR: Enone 5a, a functionalized decalin derivative, has been synthesized in up to 86% ee by an asymmetric Heck reaction starting with the allylic alcohol 3 as discussed by the authors.

Journal ArticleDOI
TL;DR: The complete dicyclopenta[a,d]cyclooctane array represented by the sesterterpene (+)-ceroplastol-I from optically pure keto ketal:tetrahydro 7'a-methylspiro[1,3-dioxolane-2,1'-inden-5'(4'H)-one] as discussed by the authors.
Abstract: Enantioselective synthesis of the complete dicyclopenta[a,d]cyclooctane array represented by the sesterterpene (+)-ceroplastol-I from optically pure keto ketal:tetrahydro 7'a-methylspiro[1,3-dioxolane-2,1'-inden-5'(4'H)-one]

Journal ArticleDOI
TL;DR: The RCu-(LiI)-TMSI reagent gives a good economy of group transfer with good to excellent yields of conjugate adducts as discussed by the authors, and is a most useful alternative to the conventional lithium diorganocuprates in conjugates.
Abstract: Conjugate additions with the efficient monoorganocopper-iodotrimethylsilane combination, exemplified mainly with methylcopper, butylcopper, and tert-butylcopper, proceed cleanly, smoothly, and rapidly to a variety of α,β-unsaturated carbonyl compounds; cyclic and acyclic enones, β-alkoxy enones, enoates and lactones in ether, THF, and dichloromethane, often at -78 o C. The RCu-(LiI)-TMSI reagent gives a good economy of group transfer with good to excellent yields of conjugate adducts. Lithium iodide, present from preparation of the organocopper compounds, increases the rate of the reactions and is a favorable component. Additions are faster, but somewhat less selective, in THF than in ether. Careful workup after addition of triethylamine or pyridine at low temperature permits isolation of TMS enol ethers and TMS ketene acetals. Acyclic enones preferentially give the Z-silyl enol ethers. The RCu(LiI)-TMSI system is a most useful alternative to the conventional lithium diorganocuprates in conjugate additions

Journal ArticleDOI
TL;DR: Bicycle enediones have been synthesized via inter-and intramolecular dicobaltoctacarbonyl-mediated cyclizations (Pauson-Khand reactions) of electron-deficient alkynones.
Abstract: Bicyclic enediones have been synthesized via inter- and intramolecular dicobaltoctacarbonyl-mediated cyclizations (Pauson-Khand reactions) of electron-deficient alkynones. Three transformations are most efficient when the reaction solvent is acetonitrile



Journal ArticleDOI
TL;DR: EuCl3 as mentioned in this paper is an efficient catalyst for Michael addition of 1,3-dicarbonyl compounds, which allows the formation of Michael adducts in an enantioselective way.

Journal ArticleDOI
TL;DR: In this article, Enone 1 reacts with electron-rich aromatic systems such as indole and N,N -dimethylaniline in the presence of a Lewis acid catalyst to give a β-arylvinyltrifluoromethylketone.

Journal ArticleDOI
TL;DR: Enantiomers of the mixture of cis and trans photocycloadducts of C 60 and 3-methylcyclohexenone were separated by HPLC on the chiral stationary phase (S,S)-Whelk-O; chiroptical properties indicate that the fullerene moiety in the strained trans cycloadduct has a skewed π-system with local C 2 symmetry as mentioned in this paper.
Abstract: Enantiomers of the mixture of cis and trans photocycloadducts of C 60 and 3-methylcyclohexenone were separated by HPLC on the chiral stationary phase (S,S)-Whelk-O; chiroptical properties indicate that the fullerene moiety in the strained trans cycloadducts has a skewed π-system with local C 2 symmetry

Journal ArticleDOI
TL;DR: In this article, the corresponding bis(allyl or homoallyl)propargyl acetal-cobalt complexes in the presence of trimethylamine Noxide were used for the formal synthesis of loganine.


Journal ArticleDOI
TL;DR: In this article, five and six-membered rings can be constructed in one flask from two different enones and trisphenylthio)methyllithium.



Journal ArticleDOI
TL;DR: Bicycle enone 23a, a functionalized decalin derivative, has been synthesized in up to 86% ee by an asymmetric Heck reaction starting with bisallylic alcohol as discussed by the authors.
Abstract: Bicyclic enone 23a, a functionalized decalin derivative, has been synthesized in up to 86% ee by an asymmetric Heck reaction starting with bisallylic alcohol 24. Enone 23a has been converted to 19, a key intermediate in the synthesis of vernolepin (14). Furthermore, bicyclic dienone 43 has been synthesized in up to 83% ee from the prochiral dienone 39

Journal ArticleDOI
TL;DR: The tricyclic enone containing the taxane ring system was synthesized using an intramolecular Ni(II)/Cr(II)-mediated coupling of β-iodoenone aldehyde 11 as the key step.

Journal ArticleDOI
TL;DR: In this article, a new strategy for the synthesis of α-hydrory ketones by samarium(II) iodide-mediated three-component coupling of organic halides, an isocyanide, and carbonyl compounds is disclosed.
Abstract: A new strategy for the synthesis of α-hydrory ketones by samarium(II) iodide-mediated three-component coupling of organic halides, an isocyanide, and carbonyl compounds is disclosed. An (α-iminoalkyl)samarium(III) species is generated in situ by treatment of an organic halide with 2 equiv of samarium(II) iodide in the presence of 2,6-xylyl isocyanide. Subsequent treatment of the mixture with a carbonyl compound affords α-hydroxy imines, which are converted by acid-catalyzed hydrolysis to the corresponding α-hydroxy ketones