Showing papers on "Enone published in 1994"
TL;DR: Arenethiolatocopper(I) complexes are shown to be efficient homogeneous catalysts in Michael addition reactions of several Grignard reagents to acyclic enones as discussed by the authors.
95 citations
TL;DR: In this paper, the asymmetric Michael addition of nitroalkanes to enones and an enal is described. But the overall transformation allows the asymmetry alkylation of enones at the β-carbon atom.
93 citations
TL;DR: A chiral scandium catalyst, prepared from trifluoromethanesulfonate (Sc(OTf) 3 ), (R)-(+) 1,1'-bi-2-naphthol, and a tertiary amine in dichloromethane, was quite effective in the enantioselective Diels-Alder reactions of acyl-1,3-oxazolidin-2 -ones with dienes as mentioned in this paper.
Abstract: A chiral scandium catalyst, prepared from scandium trifluoromethanesulfonate (Sc(OTf) 3 ), (R)-(+)1,1'-bi-2-naphthol, and a tertiary amine in dichloromethane, was quite effective in the enantioselective Diels-Alder reactions of acyl-1,3-oxazolidin-2-ones with dienes, and the corresponding Diels-Alder adducts were obtained in high yields with high diastereo- and enantioselectivities
90 citations
TL;DR: Asymmetric Michael reaction of 2-cyanopropionates with vinyl ketones or acrolein in the presence of 0.1-1 mol% of a rhodium catalyst prepared in situ from RhH(CO)(PPh3)3 and a trans-chelating chiral diphosphine ligand (S,S)-(R,R)-PhTRAP in benzene at 3-5°C gave optically active Michael adducts with high enantiomeric excesses (83-93% ee) in high yields RE
86 citations
TL;DR: In this paper, the soft nucleophiles were added to enones with moderate to high enantiomeric excess through ion-pair rather than steric control to catalyze the asymmetric Michael addition.
77 citations
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01 Jan 1994
TL;DR: In this paper, the authors proposed a halogenation reagent based on Appel crisscross cycloaddition, Bailey iodination, Barluenga deoxygenation, Barton-McCrombie cycloaromatization, Bergman rearrangement, Brandi-Guarna heterocyclization, Buchwald reducing agent, Chiatgilialoglu heterocycle synthesis, G. Enders olefin metathesis, Grubbs asymmetric epoxidation, Jacobsen asymemetric oxidation, Kagan-Modena am
Abstract: Halogenation reagent, Appel crisscross cycloaddition, Bailey iodination, Barluenga deoxygenation, Barton-McCrombie cycloaromatization, Bergman rearrangement, Brandi-Guarna heterocyclization, Buchwald reducing agent, Chiatgilialoglu heterocycle synthesis, G. Enders olefin metathesis, Grubbs asymmetric epoxidation, Jacobsen asymemetric oxidation, Kagan-Modena amine displacement, Katritzky N-Acyl rearrangement, Kawase zinc vinyl coupling, Knochel hydroxycyclopropanation, Kulinkovich oxidations, Nicolaou aminoacid synthesis, O'Donnell enone synthesis, Saegusa catalytic nitrogenation, Shibasaki chiral transfer, Yamamoto. (Part contents)
69 citations
63 citations
TL;DR: In this paper, an α-kainic acid (1SR,2SR,5RS)-ethyl (N-(benzyloxycarbonyl)-3-aza-6-oxobicyclo[3.3.0] octane-2-carboxylate (11) was synthesized in a large scale in 50% yield via the cycloaddition of thiazolium ylide and 2-cyclopentenone.
Abstract: Racemic α-kainic acid (1) has been prepared from (1SR,2SR,5RS)-ethyl (N-(benzyloxycarbonyl)-3-aza-6-oxobicyclo[3.3.0]octane-2-carboxylate (11) in ca. 16% overall yield via a concise six-step synthetic sequence. Compound (11) is prepared on a large scale in 50% yield via the [3+2] cycloaddition of thiazolium ylide (9) and 2-cyclopentenone, which pro- vides the requisite 2,3-trans, 3,4-cis stereochemical array about the trisubstituted pyrrolidine nucleus in (1). Chemoselective addition of the one-to-one adduct of MeLi and TiCl 4 to the ketone functionality in (11) followed by dehydration, oxidative ring opening, and nonbasic methylenation of the stereochemically labile C4 acetate moiety with CH 2 I 2 -Zn-TiCl 4 affords the fully protected penultimate intermediate (17) which is exhaustively hydrolyzed to provide (1). This represents a highly efficient and stereocontrolled preparation of (±)-α-kainic acid
60 citations
TL;DR: In this paper, a mechanism involving enone complexation by the Lewis-acidic zirconocene followed by inner-sphere transfer of the alkyl substituent to chelated Cu(l) is proposed.
56 citations
TL;DR: In this article, a disilylation of β,β-unsaturated ketones with 1,1-dichloro-l-phenyl 2,2,2-trimethyldisilane was performed in the presence of phosphine-palladium catalysts in benzene.
54 citations
TL;DR: In this article, two approaches for the asymmetric preparation of (−)- or (+)- α-aminobenzlactam 1 are described, one based on asymmetric hydrogenation of enamide 5 and the other based on the racemization/resolution of (±)- 1.
TL;DR: The methyl ester of the pentacyclic nucleus of ptilomycalin A has been prepared by an efficient, convergent, biogenetic, 14-step route, and has been converted to tricyclic aminals 42 and 43 by ammonolysis.
Abstract: The methyl ester of the pentacyclic nucleus of ptilomycalin A (9) has been prepared by an efficient, convergent, biogenetic, 14-step route. The key steps involve the conversion of acyclic bis enone 39 to 9 in four steps. Michael addition of O-methylisourea to 39 afforded 52% of a mixture of isoureas 40 and 41, which were both converted to 72% of tricyclic aminals 42 and 43 by ammonolysis. Deprotection of the silyl ethers with HF and cyclization with Et 3 N in MeOH afforded 9 (≃34% from 42) and the diastereomer 45 with an equatorial methyl ester group (≃26% from 42)
TL;DR: In this paper, a facile, high-yield, catalytic air-oxidation entry to verbenone from α-pinene was presented, and the entry was shown to work well in the presence of catalytic catalysts.
TL;DR: In this paper, the treatment of allylic alcohols with catalytic amounts of palladium catalysts in the presence of oxygen leads to the formation of α,β-unsaturated carbonyl compounds.
TL;DR: The first total synthesis of tricyclic enone A (1) was completed in 12 steps from 6methoxy-2-isopropyl-1-naphthol (22) in 19% overall yield at best.
Abstract: An efficient first total synthesis of (±)- and (+)-triptoquinone A (1), a novel diterpenoid quinone with significant inhibitory activity against interleukin-1 releases, has been completed. Birch reduction of tricyclic enone (±)-7, prepared from known 6-methoxy-2-isopropyl-1-naphthol (22), which is readily available in large quantities, was followed by immediate enolate trapping to provide silyl enol ether (±)-30. Compound 30 was converted into carboxylic acid (±)-4 via the corresponding enol triflate (±)-31 either by sequential palladium-catalyzed carbonylation and oxidation or by direct carboxylation. The total synthesis of (±)-1 was completed by oxidation of (±)-4 with CAN in 12 steps from 22 in 19% overall yield at best. A second, enantioselective total synthesis of (+)-1 was accomplished via (+)-7, which was prepared by (-)-N-[4-(trifluoromethyl)benzyl]cinchonidium bromide(33) catalyzed asymmetric Michael reaction of 6 with ethyl vinyl ketone and a subsequent aldol condensation
TL;DR: In this article, a diastereoselective 1,6-addition of bislactim et al. was used to deprotonate the ketone of antifun- gal natural products.
Abstract: Enantioselective and diastereoselective syntheses of the title antifun- gal natural products and some of their diastereoisomers are described. Key steps include the diastereoselective 1,6-addition of bislactim et- her (14) and a stereoselective deprotonation of ketone (17) using lit- hium (S,S)-bis(1-phenylethyl)amide as a chiral base. All natural produ- cts possess the (S)-configuration at C-1 of the substituted cyclohex- (en)yl residues of the C-terminal amino acids, which contradicts the assignments in the literature. At physiological pH most of the dipepti- des are instable and react by an intramolecular 1,4-addition with the formation of 6-oxoperhydroindoles
TL;DR: Lithium phenyldimethylsilyl(dialkyl)zincates add to a number of αβ-unsaturated carbonyl compounds to give, in most cases, higher yields of the conjugate addition product than they had achieved with the corresponding silylcuprate as discussed by the authors.
Abstract: Lithium phenyldimethylsilyl(dialkyl)zincates add to a number of αβ-unsaturated carbonyl compounds to give, in most cases, higher yields of the conjugate addition product than we had achieved with the corresponding silylcuprate.
TL;DR: In this article, the intramolecular Pauson-Khand reaction both efficiently and regioselectively was performed on 6-cyclopropylidene-1-hexynes.
TL;DR: In this article, a preparative method for the synthesis of (ω-1), ω-dioxocarboxylic acids and (ω -1)-oxoalkanedioic acids monoesters by respective oxidative cleavage of 2-substituted cycloalkane-1,3-diones and cyclic β-ketoesters, by copper perchlorate in acetonitrile in an oxygen atmosphere, is reported.
TL;DR: In this paper, the synthesis of tribenzotriquinacene 4 by a stepwise cyclization strategy involving phenyl-substituted diindan intermediates is discussed in detail.
Abstract: The synthesis of tribenzotriquinacene 4 by a stepwise cyclization strategy involving phenyl-substituted diindan intermediates is discussed in detail. Based on the determination of the anti (α) stereochemistry of the previously known phenyldiindanone 8 by standard electron impact mass spectrometry as well as on synthetical evidence (8 → 12 → 14), the conversion of 8 to the syn (β) phenyl-substituted isomer 20 by means of dehydrogenation-rehydrogenation sequences has been achieved. In particular, the preparation of the isomeric diindenones 15 and 16 as key synthetic intermediates by thermal syn elimination of the corresponding phenylsulfinyl and phenylseleninyl ketones 22 and 25 is described and contrasted to a bromination/dehydrobromination approach adopted from a previous report. The synthesis is completed by reduction of 20 to diindanol 27 followed by cyclodehydration, giving 4 in 14–19% overall yield from 8. Non-cyclizing dehydration of 27 and the isomeric diindanol 9 gives the Δ4b,9-diindene 30 as the most stable non-cyclized isomer of 4. The steric effect of the syn- or anti-oriented phenyl substituents on the preferred conformation of the diindan skeleton is deduced from the contrasting vicinal 1H-1H spin coupling observed for the stereoisomers, e.g. the 9-phenyldiindans 28 and 29.
TL;DR: Triarylstibines react with α,β-unsaturated aldehydes and ketones in acetic acid at 25°C in the presence of silver acetate and a catalytic amount of palladium(II) acetate to afford the hydroarylation products by conjugate addition in good yields as discussed by the authors.
TL;DR: SmI2 presents catalystic activity for Diels-Alder reactions between cyclopentadiene or isoprene and various dienophiles, and for hetero diels-alder reactions.
TL;DR: The Pauson-Khand reaction on the carbohydrate derived precursors was reported in this article, and the resulting bis-heteroannulated pyranosides 6−10 were obtained in moderate yields.
TL;DR: In this article, the formation of α-iodoenones from secondary alkynols with NIS/HTIB (cat), tertiary alkynol with I 2 /PDC and enones with I 1 /pyridine have been compared.
TL;DR: The 2,2-Difluorovinyl ketones readily react with heteroatom nucleophiles such as thiols, alcohols and amines to undergo stepwise replacement of the two fluorine atoms via addition-elimination process as mentioned in this paper.
TL;DR: In this paper, the angular triquinane (±)-pentalenene (1a) was synthesized by 1,2-bis((trimethylsilyl)oxy)cyclobutene (3) in the presence of boron trifluoride etherate.
Abstract: The route to the angular triquinane (±)-pentalenene (1a) followed from an efficient geminal acylation of the acetal of isophorone or its homolog 6b by 1,2-bis((trimethylsilyl)oxy)cyclobutene (3) in the presence of boron trifluoride etherate. Ring cleavage and reclosure (9→11) secured the required spiro[4.4] nonane system with a pendant ketone function in place for the closure of the final, central ring. The relative stereochemistry at C-9 was established during hydrogenation over palladium of the C-3 double bond of 11, but the facial selectivity was determined by the mode of reduction of the conjugated, orthogonal double bond at C-6 of 11. After cyclization to the enone 17b, the synthesis was completed by reductions of both the double bond and the ketone and simple dehydration. The 9-epi isomer (26) of (±) pentalenene was synthesized
TL;DR: In this paper, α,β-unsaturated ketones can be hydrogenated conveniently under catalytic transfer hydrogenation conditions using ammonium formate / Pd-C (10 %) in refluxing methanol.
TL;DR: In this article, 3-substituted chromones were synthesized by the reactions of acid anhydrides derivatives under mild conditions using enaminoketone as starting material.
Abstract: Utilizing an enaminoketone (1) as starting material, 3-substituted chromones were synthesized by the reactions of acid anhydrides derivatives under mild conditions.