Γ-unsaturated Ketones Research Articles

A New One-Pot Synthesis of 3,6-Disubstituted Pyridazines Starting from β-Nitro-β,γ-Unsaturated Ketones

AbstractA new one-pot preparation of 3,6-disubstituted pyridazines starting from β-nitro-β,γ-unsaturated ketones and hydrazine monohydrate is presented. The protocol entails two sequential steps, leading to the isolation of the title targets in satisfactory overall yields tolerating a good variety of additional functionalities.

One-Pot Synthesis of Multiarylated Benzophenones via [3 + 2 + 1] Benzannulation of Ketones, Alkynes, and α,β-Unsaturated Carbonyls

In this study, we synthesized γ-phenyl-β,γ-unsaturated ketones in situ from acetophenones and phenylacetylenes under Trofimov's conditions using KOtBu in a dimethyl sulfoxide (DMSO) solvent. The obtained ketones reacted with α,β-unsaturated carbonyls in a one-pot manner, forming tri- or diarylated benzophenones. The present reaction proceeded efficiently by one-pot manipulation with a suitable carboxylic acid.

Copper-Catalyzed Regioselective Sila-acylation and Sila-imination of Allenes Using Esters and Nitriles

AbstractThe sila-acylation of allenes is performed in the presence of a copper catalyst using PhMe2Si-B(pin) and esters as the silyl and acyl sources, respectively. β-Silyl-β,γ-unsaturated ketones are obtained regioselectively in good to high yields. The sila-imination of allenes is also achieved using nitriles as electrophiles. Exposure of the reaction mixture to air results in the production of cyclic silyl peroxides.

Modular Synthesis of 2,8-Dioxabicyclo[3.2.1]octanes by Sequential Catalysis

A modular synthesis of 2,8-dioxabicyclo[3.2.1]octane (2,8-DOBCO) ketals is realized by sequential catalysis. The key intermediates, e-hydroxyl-β,γ-unsaturated ketones, are readily available by Ni-catalyzed three-component coupling of 1,3-dienes, aldehydes, and acylzirconocene reagents. These polyfunctionalized ketones can undergo a V-catalyzed cascade of epoxidation and ring rearrangement to provide access to 6-hydroxyl-2,8-DOBCOs. Mechanistic studies indicate that the V(V) species, generated under epoxidation conditions, promotes the ring rearrangement in a stereospecific manner. Meanwhile, the e-hydroxyl-β,γ-unsaturated ketones are transformed into 6-amino-2,8-DOBCOs by a Cu-catalyzed cascade of aziridination and ring rearrangement. In the end, the one-pot approach toward 6-hydroxyl- or 6-amino-2,8-DOBCOs from 1,3-diene, aldehydes, and acylzirconocene reagents is more favorable.

Catalytic Enantioselective Vinylogous Pinacol Rearrangement

Key words vinylogous pinacol rearrangement - chiral N-triflyl-phosphoramide - α-branched-β,γ-unsaturated ketones

Direct Metal-Free Entry to Aminocyclobutenes or Aminocyclobutenols from Ynamides: Synthetic Applications.

The [2+2] cycloaddition of ynamides with the highly polarized reagent Tf2 C=CH2 has been developed to regioselectively afford bis(triflyl)aminocyclobutenes in the absence of catalyst under mild conditions. Incidentally, with the ynamides bearing electron-rich aromatic rings at the C-terminal, an interesting reactivity switch was observed; a cyclization/hydroxylation sequence yielded 2-amino-3-(triflyl)cyclobut-2-enols. Aminocyclobutene construction with addition of alcohols resulted in the formation of aminocyclobutenyl ethers through a cyclization/hydroalkoxylation process. Moreover, the utility of functionalized aminocyclobutenes as precursors for further elaboration was demonstrated with the preparation of α-amino-β,γ-unsaturated ketones and 3-(triflyl)buta-1,3-dien-2-amines through 4 π-electrocyclic ring opening.

Nano copper ferrite: A reusable catalyst for the synthesis of β, γ-unsaturated ketones

Copper ferrite nano material as reusable heterogeneous initiator in the synthesis of β, γ-unsaturated ketones and allylation to acid chlorides are presented. The reaction of allylichalides with various acid chlorides is achieved in the presence of copper ferrite nano powders at room temperature in tetrahydrofuran (THF). The present method is first of its kind in the synthesis of title compounds without any additive/ co-catalyst. The nano catalyst is easily recovered and its reusability is recorded.

Synthesis of Polycyclic Compounds Employing Palladium-catalyzed Cycloalkenylation

In 1979, Ito and Saegusa et al. discovered that the corresponding silyl enol ethers of the alkenyl ketones produce the cyclic β, γ-unsaturated ketones in the presence of palladium acetate. In addition, Kende et al. and Shibasaki et al. have individually investigated the reaction mechanism of cycloalkenylation process and the application to bioactive natural product syntheses, e.g. quadrone, phyllocladene, and capnellene derivatives.During the course of our investigations toward total syntheses of terpenoids, such as hirsutene and stemodin, we also reported synthetic routes to the bicyclo [3.3.0] octane ring system and decalin unit using Pd (II) -promoted cycloalkenylations. However, the process employing stoichiometric amounts of Pd (OAc) 2 suffers from low yields on large scale due probably to tarry Pd (0) species produced by reductive elimination. This is a serious limitation in the application of cycloalkenylation involving Pd (II).To solve this problem, we developed a novel palladium-catalyzed cycloalkenylation by applying Larock's conditions. On top of that, the methodology was successfully adapted for the synthesis of the bicyclo [3.2.1] octanes, bicyclo [3.3.0] octanes, benzo-fused bicyclo [3.3.0] octanes, and the tandem cycloalkenylation process.In this review, we would like to give a comprehensive coverage of the above-described aspects of palladium-catalyzed cycloalkenylations.

Cation exchange resin-catalysed esterification of acetic acid with 2-(1-cyclohexenyl)cyclohexanone

Self-aldol condensation of cyclohexanone yields a mixture of 2-(1-cyclohexenyl)cyclohexanone (I), 2-cyclohexylidenecyclohexanone (II) and subsequent condensation products. An acid-treated clay catalyst was employed to selectively obtain the β γ-unsaturated ketone (I). (I) was separated from the reaction mixture by fractional vacuum distillation and subsequently esterified with acetic acid to synthesise the corresponding ester, 2-(2-cyclohexyl acetate)cyclohexanone, a precursor of [1,1-biphenyl]-2,2'-diol, which has applications in plasticizers, pesticides, as a diluent in epoxy resins, etc. The applicability of cation exchange resins and an acid-treated clay for the esterification of 2-(1-cyclohexenyl)cyclohexanone with acetic acid was explored.

Allylation and benzylation of enolates derived from β-phenylselanyl silyl enol ethers

Abstract α-Phenylselanyl γ-unsaturated ketones were obtained through allylation of enolates generated by potassium t-butoxide cleavage of β-phenylselanyl silyl enol ethers derived from α-phenylselanyl ketones. With enoxysilanes prepared from α-phenylselanyl aldehydes. O-allylation and O-benzylation of the corresponding enolates were also observed.

Synthesis ofβ-Trimethylsilyl-β, γ-unsaturated Ketones via Lewis Acid Promoted Reactions of 2,3-bis(Trimethylsilyl)-propene with Acid Chlorides

Abstract Reactions of 2,3-bis(trimethylsilyl)propene with acid chlorides in the presence of aluminum chloride give β-trimethylsilyl-β,γ-unsaturated ketones in high yields.

一酸化炭素のラジカル反応を利用する新しいカルボニル化法

A novel carbonylation method based on free-radical reactions has been developed. Acyl radicals, generated by the addition of alkyl free-radicals to carbon monoxide, have been effectively trapped by tin hydride. Through this sequence, the free-radical formylation of organo halides to the corresponding aldehydes was realized. Carbonylative cyclizations to give cyclopentanones can also be affected starting with 4-pentenyl halides. When an alkene was also present in the reaction system, the trapping of the alkyl free-radical by carbon monoxide to form an acyl free-radical and the subsequent addition of that radical to the alkene took place efficiently to give an unsymmetrical ketone. This sequence represents a unique method for the double alkylation of carbon monoxide β, γ-Unsaturated ketones can be synthesized via a three-component coupling of alkyl iodides, carbon monoxide, and allylstannane. All of these findings have demonstrated that free-radical carbonylation is a useful method for the introduction of carbon monoxide into organic molecules.

Studies on Trifluoromethyl Ketones. VII. Ene Reaction of Trifluroacetaldehyde and Its Application for Synthesis of Trifluoromethyl Compounds.

As an extension of our studies on the ene reaction of trifluoromethyl ketones, the ene reaction of trifluoroacetaldehyde was examined. The aldehyde reacted with various ene compounds as a good enophile in the presence of Lewis acids, among which methylaluminum dichloride workded best, though polymerization of the aldehyde caused by the Lewis acid among which methylaluminum dichloride worked best, though polymerization of the aldehyde caused by the Lewis acid often lowered the isolation yields of the ene reaction. The ene reaction products were successfully oxidized to trifluoromethyl β, γ-unsaturated ketones with Dess Martin reagent. Reduction of the ene reaction products followed by oxidation with Jones reagent gave saturated trifluoromethyl ketones. The β, γ-unsaturated ketone rearranged on thermolysis to an α, β-unsaturated ketone. These ketones obtained were converted to otehr types of trifluoromethyl compounds. Thus, the ene reaction of trifluoroacetaldehyde provides a versatile method for synthesis of many types of trifluoromethyl compounds. During this derivatization, a trifluoromethyl group was found to behave as a much larger substituent than a decyl group.

Acyldemetallation of titanium(III) π-allylic complexes

Titanium(III) π-allylic complexes, prepared by the interaction of 1,3-dienes or trienes with Cp 2TiCl 2 and n-PrMgBr, react with carboxylic acid chlorides RCOCl (R = alkyl, aryl, alkenyl) to give β, γ-unsaturated ketones in high yields. The reaction takes place at the most substituted carbon atom of the π-allylic ligand.

ChemInform Abstract: Norrish Type II Photoreaction of 2,3‐Dihydro‐2,3‐methano‐1,4‐naphthoquinones. A Novel Photorearrangement of α,β‐Cyclopropyl Ketone to β,γ‐Unsaturated Ketone.

Irradiation of the title compounds gave cyclobutanols as the initial type II cyclization products, which were further photochemically rearranged to tricyclic β, γ-unsaturated ketones presumably via homolytic fission of cyclopropane ring followed by 1,2-alkyl migration.

On possible redirection of the course of anionic oxy-cope rearrangements

The β, γ-unsaturated ketones bicyclo[2.2.1]hept-2-en-7-one (10) and 7,7-dimethoxybicyclo[2.2.1]hept-2-en-5-one (15) have been condensed with 1-metalated trans-1-methoxybutadienes (7a or 7b) and 2-isopropenylcyclopentenes (8b or 8c). Oxyanion formation within the resulting alcohols is followed by skeletal rearrangement at room temperature. Careful product analysis has revealed the [3,3] sigmatropic reaction manifold to be followed almost exclusively. Only in the case of 13 is a modest amount (4%) of formal antarafacialretention [1,3] sigmatropic bridgehead carbon migration in evidence. Consequently, the structural features inherent to these alcohols are not conducive to redirecting electronic reorganization to an alternative isomerization process.

Norrish Type II Photoreaction of 2,3-Dihydro-2,3-methano-1,4-naphthoquinones. A Novel Photorearrangement of α, β-Cyclopropyl Ketone to β, γ-Unsaturated Ketone

Abstract Irradiation of the title compounds gave cyclobutanols as the initial type II cyclization products, which were further photochemically rearranged to tricyclic β, γ-unsaturated ketones presumably via homolytic fission of cyclopropane ring followed by 1,2-alkyl migration.

Chlorination of Acyclic β-Diketones. Formation and Stability of β-Chloro-β,γ-unsaturated Ketones

Abstract Chlorination of acyclic β-diketones with triphenylphosphine–carbon tetrachloride and the other chlorinating reagents predominantly afforded β-chloro-β,γ-unsaturated ketones except the cases of the terminal alkyl group of the diketones was methyl or t-butyl. In these reactions, the isomerization of the β-chloro-α,β-unsaturated ketones to the β,γ-unsaturated isomers was involved; the isomerization was achieved by triphenylphosphine–carbon tetrachloride as well as by some acid catalysts.

A stereoselective synthesis of the A,B,C-ring system of a triterpene, pollinastanol.

The A, B, C-ring system of a triterpene, pollinastanol, was stereoselectively constructed by intramolecular γ-alkylation of the β, γ-unsaturated ketone prepared from the thermal cycloaddition product of a benzocyclobutene derivative as a key reaction.

The reaction of trialkylstannylmethyllithium with α,β-epoxy ketones. A preparative method of β, γ-unsaturated ketones by homologation of α, gb-unsaturated ketones

α, β-epoxy ketones 2 , upon treatment with two equivalents of trialkylstannylmethyllithium 1 , afforded cyclopropanols 3 as a single product in acyclic system, and a mixture of cyclopropanols 3 and methylene 1,2-diols 4 in cyclic system. Under acidic conditions, the cyclopropanols gave β, γ-unsaturated ketones 5 in good yields.