Jack Hamelin

Catalysed esterifications in room temperature ionic liquids with acidic counteranion as recyclable reaction media

Esterification reactions of acetic acid, methoxyacetic acid and methylmalonic acid with neo-pentanol, hexanol, heptanol and decanol have been investigated in three ionic liquids with hydrogen sulphate, dihydrogen phosphate as counteranions and also two ionic liquids modified with HPF6 as catalyst. The nature of both the counteranion and cation influence the behavior of the catalyst. Good yields and high selectivities were obtained and all the produced esters could be easily recovered due to their immiscibility with the ionic liquid as green reaction medium. 2002 Elsevier Science B.V. All rights reserved.

Synthesis in dry media coupled with microwave irradiation : Application to the preparation of enaminoketones.

Abstract β-diketones react with a variety of amines and aminoesters over clay K 10 or silica under microwave irradiation in open vessels to give within a few minutes, the corresponding enaminoketones with good yields. According to the reaction conditions acylamines may also result.

Distribution of sinapine and related compounds in seeds of Brassica and allied genera

Abstract Total contents of aromatic choline esters and sinapine have been investigated in seeds of cruciferous species belonging to Arabis , Brassica , Cakile , Diplotaxs , Eruca , Hesperis , Matthiola , Raphanobrassica , Raphanus and Sinapis . Choline esters such as sinapine, isoferuloylcholine, feruloylcholine, hesperaline and 4-hydroxybenzoylcholine, have been found in many of the plants under study. Qualitative and quantitative distribution patterns of these compounds are genus-characteristic. This suggests them to be a useful tool in the chemotaxonomy of Crucifereae. In spite of their genus-specific distribution pattern, the capacity of plants to accumulate and store phenolic choline esters in seeds is highly variable within the genus Brassica . Besides a genetic control, the aromatic choline esters content is also influenced by environmental conditions. Brassica species with high and low chromosome numbers were compared according to their qualitative and quantitative aromatic choline ester content. Genomic divergence or affinity among the species under study are discussed.

L'acide diméthylsulfonium-3 propanoïque de Spartina anglica

Abstract 3-Dimethylsulphoniumpropanoic acid was isolated from Spartina anglica leaves; its structure was determined by spectroscopic methods and confirmed by comparison with a synthetic sample. It is suggested that this compound may have a role in salt resistance.

Solvent free protection of carbonyl group under microwave irradiation

Abstract Protection of aldehydes and ketones as acetals or dioxolanes catalysed by PTSA or KSF clay was readily achieved from orthoformates, 1,2-ethanediol or 2,2-dimethyl-1,3-dioxolane without solvent under microwave irradiation.

Simple Access to α, β Unsaturated Ketones by Acid-Catalyzed Solvent-Free Reactions

Abstract Various chalcones and dibenzylidene cycloalkanones were readily prepared in a few minutes with good yields by simply mixing aromatic aldehydes with substituted acetophenones or benzaldehyde with cycloalkanones in the presence of catalytic amounts of p-toluene sulfonic acid under focused microwave irradiation.

Microwave-assisted solvent-free synthesis of iminothiazolines

Abstract Several Imino 4-Thiazolines were prepared by condensation of disymmetric thioureas and α-chloro ketone under microwave irradiation in solvent free conditions. Hydrochlorides precursors were isolated. Iminothiazolines are obtained directly when reactions are performed over alumina.

1,3-DIPOLAR CYCLOADDITION OF IMIDATE YLIDES ON IMINO-ALCOHOLS : SYNTHESIS OF NEW IMIDAZOLONES USING SOLVENT FREE CONDITIONS

Abstract Imidates derived from α-amino esters as potential azomethine ylides, undergo 1,3-dipolar cycloaddition with imino-alcohols, in tautomeric equilibrium with 1,3-oxazolidines, without solvent at 70°C or under microwave irradiation. This reaction leads to a wide range of novel polyfunctionalized 4-yliden-2-imidazolin-5-ones in good yields with short reaction times. The reactivity of these imidates derived from α-amino esters with imino-alcohols is rationalized from the energy of the Frontier Molecular Orbitals (FMO) determined by semi-empirical PM3 calculations: the reaction is controlled by the interaction HOMO (1,3-dipole) - LUMO (dipolarophile) and the second order pertubation energy calculations are in agreement with the experimental reaction orientation.

Alkali metal fluoride mediated Silyl-Reformatsky reaction in solid-liquid media; activation by microwaves

Abstract Condensation of trimethylsilylacetonitrile or ethyltrimethylsilyacetate with benzaldehyde, in the presence of dried alcali metal fluorides in heterogeneous media under microwaves leads readily to β-trimethylsilyloxynitrile or ester according to a Reformatsky type reaction. The later products could be hydrolyzed and dehydrated on the wet inorganic salt to give the corresponding alkenes.

New access to functionalized dichlorophosphines: synthesis of two coordinated phosphorus heterocycles

Abstract An easy access to functionalized dichlorophosphines 2, 4, 5, 7 is described, and these compounds are dehydrochlorinated in situ with DABCO and trapped by a diene or a diazocompound to give phosphabenzenes or diazaphospholes.