Abdallah Karim

Terpenic olefin epoxidation using metals acetylacetonates as catalysts

Abstract Efficient epoxidation of natural terpenic olefins is performed using nickel acetylacetonate, oxygen and a branched aldehyde at ambient temperature. Total conversions are achieved with selectivities up to 90% into epoxide. Under the same conditions other catalytic systems using transition metal acetylacetonates (M n (acac) n ) have been used, some of which also gave satisfactory results.

Selective palladium-catalysed functionalization of limonene: synthetic and mechanistic aspects

Abstract The scope and limitation of palladium-catalysed functionalization of limonene have been investigated. Various catalytic combinations were examined in order to select the most efficient system for conversion of this substrate into allylic esters, ethers or alcohols in acetic acid, methanol and water, respectively. It appears that under mild conditions the chemoselectivity was always high as only oxidation products were formed. Moreover, by a judicious choice of ligands and/or reoxidant of palladium, the reaction can be directed mainly toward the formation of functionalized compounds having their allylic double bond in either exocyclic or endocyclic position. In both cases, the trans isomer is the major product. In order to explain these results, a mechanism is proposed involving an external nucleophile attack on a bis ( π -allyl– π -olefin) palladium complex, which was isolated under acetoxylation reaction conditions.

Catalytic oxidation of α-pinene by transition metal using t-butyl hydroperoxide and hydrogen peroxide

Abstract The allylic oxidation of α-pinene 1 was investigated using various catalytic systems. By a proper choice of the latter, the reaction can be directed toward the selective synthesis of verbenol 2 or verbenone 3 . High yield into verbenone was achieved under mild conditions with copper salts as catalysts and t -butyl hydroperoxide (TBHP) as oxidant. On the other hand, when Pd(acac) 2 was used with hydrogen peroxide, verbenol was obtained as the main product.

Hydrogenation asymetrique des dehydroaminoacides catalysee par des complexes rhodium-aminophosphine phosphinite. Influence de la structure des chelates

Abstract Asymmetric hydrogenation of dehydroaminoacids catalyzed by [Rh-L∗2] moieties (L∗2 - aminophosphine phosphinite) is performed with a good activity and allows optical yields of 90% in the case of acetamidoacrylic acid with the [Rh(COD)-(PPh2O) CHCH 2 CH(COR)N(PPh 2 )C H2]+ ClO4− system (R = O(CH2)2OC2H5). The product configuration and the enantioselectivity has been correlated to both the acyclic or cyclic structure of the ligand and the nature of the alkyl or aryl substituent in the chelating phosphine.

Asymmetric hydrogenation of activated keto compounds catalyzed by new chiral peralkyl-AMPP rhodium complexes

Abstract Readily available peralkyl aminophosphinephosphinite ligands (alkyl-AMPP ★ ) give neutral rhodium complexes active for the catalytic reduction of some activated ketones under atmospheric hydrogen pressure at ambient temperature (ee = 80 %).

New diphosphinite ligands derived from mannitol for rhodium catalyzed enantioselective hydrogenation of ketones

Abstract We have developed new electron rich chiral bisphosphinites from mannitol. The new ligands have been found to be efficient chiral auxiliaries for rhodium catalyzed hydrogenation of functionalized ketones leading to hydroxy compounds in up to 86% ee.

Hydrosilylation asymetrique de l'acetophenone catalysee par des complexes au rhodium chelates par des ligands aminophosphinite et aminophosphine-phosphinite

Abstract Chiral aminophosphinite and aminophosphine-phosphinite rhodium complexes catalyse the hydrosilylation of acetophenone (e.e.43 %)

Friedel-Craft Acylation of ar-Himachalene: Synthesis of Acyl-ar-Himachalene and a New Acyl-Hydroperoxide

Friedel-Craft acylation at 100 °C of 2,5,9,9-tetramethyl-6,7,8,9-tetrahydro-5H-benzocycloheptene [ar-himachalene (1)], a sesquiterpenic hydrocarbon obtained by catalytic dehydrogenation of α-, β- and γ-himachalenes, produces a mixture of two compounds: (3,5,5,9-tetramethyl-6,7,8,9-tetrahydro-5H-benzocyclohepten-2-yl)-ethanone (2, in 69% yield), with a conserved reactant backbone, and 3, with a different skeleton, in 21% yield. The crystal structure of 3 reveals it to be 1-(8-ethyl-8-hydroperoxy-3,5,5-trimethyl-5,6,7,8-tetrahydronaphthalen-2-yl)-ethanone. In this compound O-H…O bonds form dimers. These hydrogen-bonds, in conjunction with weaker C-H…O interactions, form a more extended supramolecular arrangement in the crystal.

Ni(0)-CMC-Na Nickel Colloids in Sodium Carboxymethyl-Cellulose: Catalytic Evaluation in Hydrogenation Reactions

A recyclable catalyst, Ni(0)-CMC-Na, composed of nickel colloids dispersed in a water soluble bioorganic polymer, sodium carboxymethylcellulose (CMC-Na), was synthesized by a simple procedure from readily available reagents. The catalyst thus obtained is stable and highly active in alkene hydrogenations.

Two atropisomers of tri­carbonyl­[η6-7-chloro-3-(3-chloro-2-methyl­phenyl)-2,4,8-tri­methyl-1,2,3,4-tetra­hydro-2,4-dibora-1,3-di­aza­naphthalene]­chromium(0)

The structures of two atropisomers of the title compound, [Cr(C16H18B2Cl2N2)(CO)3], are reported. For both compounds, the Cr(CO)3 moiety is bound to the C6 aromatic ring of the molecule; the existence of atropisomers resulting from the non-equivalence of both faces of the C6 aromatic ring is a consequence of the 3-chloro-2-methylphenyl ring being nearly perpendicular to the mean plane of the 2,4-dibora-1,3-diazanaphthalene ring. The orientation of the Cr(CO)3 tripod relative to the C6 aromatic ring is such that it is nearly eclipsed in one isomer (2.4 degrees rotation from being eclipsed with C--N, C--Cl and C--H) and slightly twisted (16.2 degrees ) from an eclipsed conformation in the other.