Αβ-unsaturated Carbonyl Compounds Research Articles

Acidic ionic liquids based on phosphonium chloride and metal chlorides-recyclable media and catalysts in the Diels-Alder reaction

Acidic ionic liquids based on phosphonium chloride and metal chlorides-recyclable media and catalysts in the Diels-Alder reaction Acidic ionic liquids based on trihexyltetradecylphosphonium chloride-P6.6.6.14 Cl and six different metal chlorides (YCl3, YbCl3, MgCl2, ZnCl2, CuCl2, InCl3) were prepared. The molar fraction of metal chloride (XMClx) used for the formation of acidic ionic liquids with P6.6.6.14 Cl was changed in the range from 0.3 to 0.5. The high catalytic activity in the Diels-Alder reaction of cyclopentadiene and various αβ-unsaturated carbonyl compounds showed ionic liquids at XMClx≤0.4. In general, the highest product yields and endo:exo ratios were achieved in the acidic ionic liquids formed from MgCl2, YCl3 and YbCl3. Thermogravimetric analysis suggested that the prepared ionic liquids were thermally stable up to nearly 400°C. Additionally, they could be reused with only little loss of catalytic activity after the 4th recycle.

Allelochemicals as Inhibitors of Glutathione S-Transferases in the Fall Armyworm

Abstract Glutathione S -transferases (GSTs) isolated from larval midguts of the fall armyworm, Spodoptera frugi perda , were used to study their sensitivity to inhibition by 44 chemicals, most of which were plant allelochemi cals. Many flavonoids, other phenols, and α,β-unsaturated carbonyl compounds were potent inhibitors of the enzymes. For the flavonoids, apigenin was the best inhibitor among those studied, showing an I 50 value of 8.2 × 10 −7 M. In general, flavonols exhibited higher inhibitory potencies than flavones; flavonoid glycosides were less inhibitory than their corresponding aglycones. In the case of phenols, tannic acid was the best inhibitor among those tested, showing an I 50 value of 2.0 × 10 −7 M. The organotin compound chlorotriphenyltin was an potent as tannic acid in inhibiting the transferases. For the αβ-unsaturated carbonyl compounds, ethacrynic acid was the most potent inhibitor among those examined, showing an I 50 value of 1.5 × 10 −7 M. However, the isothiocyanates were found to be marginal inhibitors of GSTs. GSTs isolated from larval fat bodies showed differential sensitivity to inhibition by some selected inhibitors compared with midgut GSTs. Kinetic studies of midgut GSTs revealed that ellagic acid exhibited a noncompetitive inhibition toward 1-chloro-2, 4-dinitrobenzene (CDNB) but a competitive inhibition toward glutathione (GSH). In contrast, inhibition by tannic acid and ethacrynic acid were noncompetitive toward both CDNB and GSH. Diethyl maleate did not affect GSH levels in midguts when larvae were topically treated with this compound for up to 24 h.

METHYLTRIPHENYLPHOSPHONIUM TETRAHYDROBORATE (MePh3PBH4). A STABLE, SELECTIVE AND VERSATILE REDUCING AGENT

Methyltriphenylphosphonium tetrahydroborate as a stable quaternary phosphonium borohydride is introduced. This compound is able to reduce aldehydes, ketones, acyl chlorides, and azides efficiently in CH2Cl2 αβ-Unsaturated carbonyl compounds are reduced selectively via 1,2-reduction. The effect of Lewis acids upon the mode and the rate of the reaction of epoxides and acetophenone are also described. This reagent is also able to bring about reductions effectively in the absence of solvent.

Asymmetric titanium-catalysed Michael addition of O-benzylhydroxylamine to αβ-unsaturated carbonyl compounds: synthesis of β-amino acid precursors

A new titanium-catalysed Michael type addition of O-benzylhydroxylamine to αβ-unsaturated N-acylated 1,3-oxazolidinones giving β-amino acid precursors has been developed. The reaction is catalysed by TiX2–TADDOLate and TiCl2–BINOLate complexes and good conversions with enantiomeric excesses up to 42% were obtained with the application of 10 mol% of the catalyst. In order to determine the absolute stereochemistry of the enriched enantiomer one of the products, 3-(3-benzyloxyaminobutanoyl)-1,3-oxazolidin-2-one, was converted into methyl 3-benzoylaminobutanoate. Based on the absolute stereochemistry of the Michael type addition product the mechanism for the addition step is discussed, as well as the structure of the active intermediate.

Biotransformation of αβ-unsaturated carbonyl compounds: sulfides, sulfoxides, sulfones, nitriles and esters by yeast species: carbonyl group and carbon–carbon double bond reduction

The reduction of αβ-unsaturated ketones with γ-sulfide, sulfoxide, sulfone, nitrile and ester functions has been investigated. Both CO and CC reduction was observed. In the sulfur series, CO bond reduction was always observed, but significant CC bond reduction was observed only with the sulfide. The unsaturated nitriles gave the corresponding alcohol as the major bioreduction product, with smaller but significant amounts of fully reduced product. A similar result was obtained with the ester substrate. Relative and absolute configurations of bioreduction products were determined. A comparison was made between reductions catalysed by bakers' yeast (Saccharomyces cerevisiae) and by other yeasts (Zygosaccharomyces rouxii, Pichia capsulata, P. farinosa, Candida chalmersi and C. diddensiae). The tendency of Z. rouxii to give products enantiomeric with those obtained using S. cerevisiae was noted. The relationship between substrate structure and the stereochemistry of CC double bond reduction is discussed.

Conjugate addition of the phenyldimethylsilyl group to αβ-unsaturated carbonyl compounds using a silylzincate in place of the silylcuprate

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.

Reactions on solid supports part IV: Reactions of αβ-unsaturated carbonyl compounds with indoles using clay as catalyst

Indoles react with αβ-unsaturated carbonyl compounds in the presence of clay catalysts to give substituted indoles in good yields; in one case a 3-benzyl substituent already present migrated to the 2-position, being displaced by the incoming electrophile, thus confirming that electrophilic substitution in indole occurs primarily at the 3-position.

Synthesis of α,β-unsaturated carbonyl compounds by successive rearrangement and peterson olefination of β′-hydroxy-α,β-epoxysilanes

The reaction of β′-hydroxy-α,β,-expoxysilanes with boron trifluoride–diethyl ether results in rearrangement of the epoxysilane skeleton followed by Peterson olefination, leading to αβ-unsaturated carbonyl compounds.

Reactions of iodine(I) azide with αβ-unsaturated carbonyl compounds

The addition of iodine(I) azide to some αβ-unsaturated esters and ketones has been examined. Addition to the esters under nitrogen gives products consistent with a radical pathway. Preliminary kinetic results indicate that addition of iodine(I) azide to αβ-unsaturated ketones in the presence of air involves a slow electrophilic attack. Reaction with methyl trans-cinnamate under these conditions does not go to completion.

Effects of neighbouring hydroxy-groups in metal–ammonia reductions of αβ-unsaturated carbonyl compounds

The regiospecific metal–ammonia reductions of both cis-8-hydroxy-7,11,11-trimethylspiro[5·5]undeca-1,4-dien-3-one (2a) and its metal alkoxides (2b) and (2c) could be achieved as a result of the proximity of the hydroxy-group to afford t-8-hydroxy-t-7, 11, 11-trimethyl-(6rC1)-spiro[5·5]undec-1-en-3-one (4) in high yield.

Copper(i)-catalysed conjugate reduction of αβ-unsaturated carbonyl compounds by lithium aluminium hydride

CuI catalyses an efficient conjugate reduction of αβ-unsaturated carbonyl compounds by LiAlH4 in the presence of hexamethylphosphoric triamide at –78 °C.

Heterodiene syntheses. Part 23. Zwitterions as intermediates in the formation of Michael adducts or as stable products of the reaction between 2-oxoindolin-3-ylidene derivatives with enamines or aminals

1-t-Butyl-1-aminoethylenes [(E1)–(E3)] react with N-substituted 2-oxoindolin-3-ylidene derivatives (1a–c) to give Michael-type adducts but the reactivity of diaminoethylenes [(A1)–(A3)] depends on the nature of substituents. 1,1-Dimorpholinoethylene (A1) undergoes Michael reaction with all the substrates tested but 1,1-dipiperidinoethylene (A2) only with the N-methyl- and N-benzyl-darivatives (1a and b). However, stable zwitterions are formed by (A2) with the N-acetyloxoindoline derivative (1c) and by 1.1 -dipyrrolidinoethylene (A3) with all substrates. Their structure, determined by chemical and spectroscopic methods and by X-ray analysis, is the same as that of the intermediates proposed for the reaction between αβ-unsaturated carbonyl compounds and enamines. The reason for the alternative products, i.e. Michael adducts or stable zwitterions, is discussed in terms of the effect of substituents in stabilizing the charges of the zwitterion and also in terms of frontier-orbital interaction.

Regiospecific synthetic routes to α-seleno carbonyl compounds and to αβ-unsaturated carbonyl compounds

Regiospecific synthetic routes to α-seleno carbonyl compounds and to αβ-unsaturated carbonyl compounds

New synthesis of β-substituted alkyltin halides via halogenostannane intermediates

β-Substituted ethyltin trihalides and bis-(β-substituted ethyl)tin dihalides can be prepared via the in situ reaction of αβ-unsaturated carbonyl compounds with active halogenostannane intermediates produced from halogen acids and tin(II) chloride or halogen acids and metallic tin, respectively.

Conformations of some αβ-unsaturated carbonyl compounds. Part VII. Assignments of Raman and infrared spectra of dimethyl, diethyl, and di-n-butyl fumarates and maleates

Raman and i.r. spectra of dimethyl, diethyl, and di-n-butyl fumarates and maleates in the liquid (or solid) state at room temperature (or above) and as frozen solids are reported together with vibrational assignments for conformers (trans,trans⇄trans,cis for the fumarates, cis,trans only for the maleates). Measurement of intensities of selected Raman bands at various low temperatures leads to calculation of enthalpy differences (ΔH0± standard deviation) of 396 ± 42 and 219 ± 28 cal mol–1 between the high and low energy forms of the di-n-butyl and diethyl fumarates, respectively. Dimethyl fumarate is a solid at room temperature; measurement of Raman band intensities at higher temperatures leads to a corresponding value of 774 ± 184 cal mol–1. These results provide general support for a previous result based on i.r. measurements.

Synthesis of heterocyclic compounds. Part XXX. Reactions of o-alkylamino- and o-dialkylamino-anilines with some αβ-unsaturated carbonyl compounds

The condensation of o-alkylamino- and o-dialkylamino-anilines with diethyl ethoxymethylenemalonate gave intermediates which could be cyclised to 4-quinolone derivatives. In phosphoryl chloride, the intermediate from N-(o-aminophenyl)pyrrole gave pyrrolo[1,2-a]quinoxaline. 4-Quinolones were also prepared by the reaction of o-dialkylaminoanilines with dimethyl acetylenedicarboxylate, followed by thermal cyclisation. The intermediate from N-(o-aminophenyl)pyrrole gave a pyrrolo[1,2-a]quinoxaline derivative. o-Dialkylaminoanilines attacked the β-carbon atom of methyl acrylate but the resulting intermediates could not be cyclised. The corresponding reactions with methyl methacrylate and methyl crotonate gave amides, via attack at the ester carbonyl group. With acetylacetone, the intermediate imine was formed, but failed to cyclise in polyphosphoric acid or its ethyl ester.

Radiation effects on aryl glycosides. Part VII. Radiolysis of aqueous solutions of p-nitrophenyl β-D-glucopyranoside

Pulse radiolysis experiments demonstrate that reactions of eaq–(k2= 4 x 1010 I mol–1) and OH (k2= 2.1 x 109 I mol–1 s–1) with p-nitrophenyl β-D-glucopyranoside (pNPG) yield transient species with absorption maxima near 300 nm. The results indicate that reactions occur mainly at the nitro-group. A transient species with absorption maximum at 450 nm in N2O-saturated and in acidic solution is considered to be the nitrocyclohexadienyl radical. p-Nitrophenol, 4-nitrocatechol, glucose, 2-hydroxy-4-nitrophenyl β-D-glucopyranoside, and traces of αβ-unsaturated carbonyl compounds are produced during steady state 60Co γ-irradiation of pNPG solutions, as a result of initial reaction of hydroxyl radicals. A mechanism is advanced for the formation of these products.

Conformations of some αβ-unsaturated carbonyl compounds. Part V. Assignments of Raman and infrared spectra of methyl and [2H3]methyl acrylates and trans-crotonates

Raman and i.r. spectra of methyl and [2H3]methyl acrylates and trans-crotonates in the liquid state at room temperature and as frozen solids are presented together with vibrational assignments for particular conformers. Intensities of selected Raman bands at different temperatures lead to enthalpy differences (ΔH0± standard deviation) of 377 ± 56 cal mol–1 between the high and low energy forms of methyl trans-crotonate, in very good agreement with a previous result based on i.r. measurements.

Conformations of some αβ-unsaturated carbonyl compounds. Part VI. Comparison of out-of-plane olefinic CH deformation vibrations

A comparison is made between the corresponding out-of-plane CH deformation modes in the compounds CH2:CMe·CO·OX, CH2:CHCO·OX, and MeCH:CH·CO·OX for nine different substituents X. The results provide reinterpretations of assignments, evidence of interactions between modes of a type in contrast to any expected resonance interactions, and some new considerations of conformational equilibria.

Chlorination of αβ-unsaturated carbonyl compounds. Part V. Mechanism of chlorination of αβ-unsaturated ketones in methanol and in trifluoroacetic acid

The kinetics and products of the reaction of chlorine with 1-phenyl-3-arylprop-2-enones and with 4-arylbut-3-en-2-ones in methanol have been studied. The reactions involve predominant trans-addition of the elements of methyl hypochlorite to the double bond with little formation of dichlorides, and are interpreted in terms of the formation of an open or partially-bridged carbocation which is captured by the solvent mainly prior to appreciable rotation about the carbon–carbon bond. Some catalysis by hydrogen chloride is apparent in the reaction with 4-phenylbut-3-en-2-one and is believed to involve the formation of acetals prior to reaction with chlorine. In contrast the reaction of 1,3-diphenylprop-2-enone and of 4-phenylbut-3-en-2-one with chlorine in trifluoroacetic acid gives appreciable yields of the excepted dichlorides, probably through a mechanism involving ion-pairs.