Abdelkhalek Riahi

Synergy or Competition between Palladium-Catalysis and KF/Alumina-Mediation for the Allylic Substitution of the Acetates of Baylis-Hillman Adducts by Phenols

Abstract The addition of various substituted phenols [XC6H4OH, X=H, o-CHO, o-CO2Me, o-CO2CH2Ph, o-CN, m-NHCOMe, m-OMe, p-OMe, p-CHO, p-Cl] to allylic acetates obtained from Baylis–Hillman adducts [RCH(OAc)C(CH2)CO2Et, R=H, n-Pr] has been studied in the presence of a Pd(0) catalyst and/or KF/alumina. In some cases, the use of one of these two reagents was sufficient to promote the OAc/OAr exchange but in general, faster reactions and higher yields were achieved when both reagents were used together. Evidence for two routes, an η3-allylpalladium intermediate and a Michael addition/elimination, was then obtained while a Heck type reaction could be involved under neutral conditions.

Catalytic asymmetric protonation of fluoro-enolic species: access to optically active 2-fluoro-1-tetralone

Abstract Three racemic α-fluorinated benzyl β-ketoesters have been synthesized by electrophilic fluorination with Selectfluor™. They were submitted to our well established palladium-mediated cascade reaction (deprotection, decarboxylation and protonation of the resulting enolic species) producing optically active α-fluoro ketones. With benzyl 2-fluoro-1-tetralone-2-carboxylate as substrate, ( S )-(−)-2-fluoro-1-tetralone with up to 65% enantiomeric excess was obtained using quinine as the chiral base and Pd/C type 807104 from Merck as the heterogeneous catalyst.

Catalysed Asymmetric Protonation of Simple Linear Keto-Enolic Species − A Route to Chiral α-Arylpropionic Acids

The reaction cascade consisting of deprotection/decarboxylation/asymmetric protonation of enolic species, starting from open-chain benzyl β-oxo esters, has been studied. When carried out in the presence of catalytic amounts of cinchonine, the reaction gave optically active α-aryl ketones with up to 75% ee. Enantio-enriched (S)-3-phenyl-2-butanone can be converted into 2-phenylpropionic acid without racemisation. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Homogeneous chromium(VI)-catalyzed oxidations of allylic alcohols by alkyl hydroperoxides: Influence of the nature of the alkyl group on the product distribution

Abstract The chromium oxide-catalyzed oxidation of allylic alcohol - R 1 CH(OH)CR 2 CHR 3 - by ROOH (R= t -Bu, PhCMe 2 ) affords generally a mixture of R 1 COCR 2 CHR 3 and R 1 CHCR 2 COR 3 . The rate of the reaction and the ratio between the two oxidized compounds both depend on the nature of R. It has been concluded that the oxidative species and the reactive intermediates contain this R group.

Palladium-catalyzed allylic oxidation of 1-(p-toluenesulfonyl)-2-propene and 1-(trimethylsilyl)-1-(p-toluenesulfonyl)-2-propene

Abstract The course of palladium-catalyzed oxidation of a terminal alkene by t-BuOOH or by O 2 /H 2 O is greatly modified when the allylic carbon bears a p -toluenesulfonyl substituent, and allylic oxidation results. Mechanistic explanations of this observation are proposed.

Access to optically active linear ketones by one-pot catalytic deprotection, decarboxylation, asymmetric tautomerization from racemic benzyl β-ketoesters

Benzyl 2-benzoyl-2-phenylpropanoate 1b subjected to heterogeneous hydrogenolysis conditions in the presence of catalytic amounts of commercially available cinchonia alkaloids as chiral protic source, led to (R)-1,2-diphenylpropanone with up to 71% ee, through a cascade reaction involving deprotection, decarboxylation and asymmetric tautomerization of enolic species.

2-ALKYLIDENE-1-TETRALONES FROM ALDOL CONDENSATIONS

Abstract The crotonisation of 1-tetralone with various alkyl aldehydes under basic conditions led to the corresponding 2-alkylidene-1-tetralones with fair yields and complete stereoselectivities. The E-stereochemistry of the adducts has been determined through their photoisomerisation and by comparison of the 1H NMR spectra.

On the decarboxylation of 2-methyl-1-tetralone-2-carboxylic acid – oxidation of the enol intermediate by triplet oxygen

The formation of 2-methyl-1-tetralone from the metal-free and base-free decarboxylation of 2-methyl-1-tetralone-2-carboxylic acid involves 2-methyl-3,4-dihydro-1-naphthol as an intermediate. The reaction of this enol with atmospheric oxygen leads to 2-hydroperoxy-2-methyl-1-tetralone. The oxidation mechanism is confirmed by quantum chemical calculations at the (U)B3LYP/6-31G(d) level of theory.

Efficient Approach for the Synthesis of Novel Functionalized Isoxazolines from Limonene

Abstract New functionalized isoxazolines were effeciently and easily prepared from limonene. The procedure involves a peri‐ and regioselective 1,3‐dipolar cycloaddition of nitrile oxides on the monoterpene external double bond, followed by a highly chemoselective RuCl3‐NaIO4 oxidative cleavage of the internal one. All the newly prepared isoxazolyl‐ketoacids were fully characterized from their spectroscopic data.

Synthesis, Characterization, Antimicrobial Activity, and Docking Studies of New Triazolic Tripodal Ligands

The synthesis and characterization of new N‐donor bitriazolic tripods were reported. The in vitro antibacterial and antifungal activities of these products were screened against fungal strain (Candida pelliculosa) and against four bacterial strains (Micrococcus luteus, Bacillus subtilis, Listeria innocua, and Escherichia coli). Biological data revealed the effect of the chemical structure on antimicrobial activity. Molecular docking studies of some compounds showed that they could act as inhibitors for the biotin carboxylase enzyme.