Imageability ratings across languages

Imageability is a psycholinguistic variable that indicates how well a word gives rise to a mental image or sensory experience. Imageability ratings are used extensively in psycholinguistic, neuropsychological, and aphasiological studies. However, little formal knowledge exists about whether and how these ratings are associated between and within languages. Fifteen imageability databases were cross-correlated using nonparametric statistics. Some of these corresponded to unpublished data collected within a European research network-the Collaboration of Aphasia Trialists (COST IS1208). All but four of the correlations were significant. The average strength of the correlations (rho = .68) and the variance explained (R (2) = 46%) were moderate. This implies that factors other than imageability may explain 54% of the results. Imageability ratings often correlate across languages. Different possibly interacting factors may explain the moderate strength and variance explained in the correlations: (1) linguistic and cultural factors; (2) intrinsic differences between the databases; (3) range effects; (4) small numbers of words in each database, equivalent words, and participants; and (5) mean age of the participants. The results suggest that imageability ratings may be used cross-linguistically. However, further understanding of the factors explaining the variance in the correlations will be needed before research and practical recommendations can be made

New Enantiopure P,P-Bidentate Bis(diamidophosphite) Ligands. Application in Asymmetric Rhodium-Catalyzed Hydrogenation

Two series of new enantiopure bidentate bis­(diamidophosphite) ligands with diazaphospholidine and diazaphosphepine heterocyclic backbones were prepared. The ligands have a highly modular structure, which is well suited to the synthesis of a small library of compounds. Preparation was accomplished by the successive addition of enantiomerically pure substituted diamines (<i>N,N</i>′-dibenzylcyclohexane-1,2-diamine (<b>1</b>), <i>N,N</i>′-dimethylcyclohexane-1,2-diamine (<b>2</b>), and <i>N,N</i>′-dimethyl-1,1′-binaphthyl-2,2′-diamine (<b>3</b>)) and enantiomerically pure diols (butanediol (<b>a</b>), cyclohexanediol (<b>b</b>), di-<i>O</i><b>-</b>isopropylidenethreitol (<b>c</b>), and binaphthol (<b>d</b>)) to phosphorus trichloride. The corresponding bis­(diamidophosphite) selenides were prepared, and the ¹<i>J</i>_PSe values were calculated in order to evaluate the σ-donor ability of the new ligands. The cationic Rh­(I) complexes [Rh­(COD)­(P,P)]­BF₄ were synthesized with 8 of the 12 new bis­(diamidophosphite) ligands. The complexes were used as catalytic precursors for the asymmetric hydrogenation of benchmark substrates, namely methyl α-acetamidoacrylate (<b>4</b>), methyl (<i>Z</i>)-α-acetamidocinnamate (<b>5</b>), and dimethyl itaconate (<b>6</b>). The influence of the nature of both the terminal and bridging fragments of the bis­(diamidophosphite) ligands on the asymmetric induction is discussed. Most proved to be effective catalysts for the process, attaining total conversion and excellent enantioselectivity (>99% ee) with the complex containing the (<i>R</i>;<i>R</i>_al,<i>R</i>_al<i>;R</i>)<i>-</i><b>3c</b> ligand in the hydrogenation of the three substrates. The best performing catalytic precursor [Rh­(COD)­((<i>R</i>;<i>R</i>_al,<i>R</i>_al;<i>R</i>)<i>-</i><b>3c</b>)]­BF₄ was tested in the hydrogenation of selected cyclic enamides (<b>7</b>–<b>9</b>) and β-acetamidoacrylate (<b>10</b>)

Asymmetric allylic alkylation catalyzed by Pd(II)-complexes with (S)-BINPO, a hemilabile axially chiral P, O-heterodonor inducer

A complex generated in situ from [Pd(&#x3b7;3-C3H5)Cl]2 and (S)-BINPO 1 is an active catalyst in the asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl esters 6 via a malonate anion with ee's up to 81% being obtained. Rate and stereoselectivity of the reaction are dramatically influenced by the solvent. The Pd-complex [(S)-(BINPO)Pd(&#x3b7;3-1,3-diphenylallyl)] 5has been synthesized and its structure in the solid state determined by X-ray diffraction. The stoichiometric reaction of 5 with malonate anion affords the alkylated product of the same configuration as the one obtained in the catalytic reaction at room temperature in nearly identical enantiomeric purity (71%)

Efficient Palladium Catalysts Containing Original Imidazolium-Tagged Chiral Diamidophosphite Ligands for Asymmetric Allylic Substitutions in Neat Ionic Liquid

New imidazolium-tagged chiral diamidophosphite ligands, (<i>S</i>,<i>S</i>)-<b>a</b> and (<i>R</i>)-<b>b</b>, derived from (<i>S</i>,<i>S</i>)-<i>N</i>,<i>N</i>′<i>-</i>dibenzyl-1,2-cyclohexanediamine and (<i>R</i>)-<i>N</i>,<i>N</i>′-dimethyl-1,1′-binaphthyl-2,2′-diamine, respectively, and the corresponding palladium allylic complexes of general formula [PdCl­(η³-2-Me-C₃H₄)­(κ¹<i>P</i>-L)]­BF₄ (<b>1a</b>,<b>b</b>) and [Pd­(η³-2-Me-C₃H₄)­(κ¹<i>P</i>-L)₂]­(BF₄)₃ (<b>2a</b>,<b>b</b>) were synthesized and fully characterized, including the X-ray crystal structure for <b>1b</b>. These original Pd/L catalytic systems were applied in asymmetric allylic alkylation, amination, and sulfonylation using <i>rac</i>-3-acetoxy-1,3-diphenyl-1-propene as a substrate in neat ionic liquids, [bmim]­[PF₆] and [Pyr]­[NTf₂]. The best results in terms of enantioselectivity were obtained with the catalytic precursor <b>1b</b> in [Pyr]­[NTf₂]. The catalytic phase containing <b>1b</b> for the allylic amination could be recycled up to six times without significant loss of asymmetric induction

Metal Complexes Containing Enantiopure Bis(diamidophosphite) Ligands in Asymmetric Allylic Substitution and Hydroformylation Reactions

Enantiopure bis­(diamidophosphite) ligands with a heterocyclic terminal fragment derived from (<i>R</i>)- and (<i>S</i>)-<i>N</i>,<i>N</i>′-dimethyl-1,1′-binaphthyldiamine and bridging fragments derived from (<i>S</i>,<i>S</i>)-2,3-butanediol (<b>a</b>), (4<i>R</i>,5<i>R</i>)-4,5-di­(hydroxymethyl)-2,2-dimethyl-1,3-dioxolane (<b>b</b>), and (<i>R</i>)- and (<i>S</i>)-1,1′-bi-2-naphthol (<b>c</b>) were used to prepare the palladium complexes with general formula [Pd­(η³-2-CH₃-C₃H₄)­(P-P)]­[X] (X = PF₆, <b>1a</b>-(<i>S;S</i>_<i>al</i><i>,S</i>_<i>al</i><i>;S</i>), <b>1b</b>-(<i>R;R</i>_<i>al</i><i>,R</i>_<i>al</i><i>;R</i>), <b>1b</b>-(<i>S;R</i>_<i>al</i><i>,R</i>_<i>al</i><i>;S</i>), <b>1c</b>-(<i>R;R</i>_<i>al</i><i>;R</i>), <b>1c</b>-(<i>R;S</i>_<i>al</i><i>;R</i>); X = BPh₄, <b>2a</b>-(<i>R;S</i>_<i>al</i><i>,S</i>_<i>al</i><i>;R</i>), <b>2c</b>-(<i>R;R</i>_<i>al</i><i>;R</i>)), which have been fully characterized. The solid-state structure for complexes <b>1a</b>-(<i>S;S</i>_<i>al</i><i>,S</i>_<i>al</i><i>;S</i>) and <b>1b</b>-(<i>R;R</i>_<i>al</i><i>,R</i>_<i>al</i><i>;R</i>) has been determined by X-ray diffraction. The catalytic performance of the palladium complexes has been evaluated in asymmetric allylic alkylation and amination reactions with the benchmark substrate. The influence of the nature and absolute configuration of both the terminal and bridging fragments of the bis­(diamidophosphite) ligands on the asymmetric induction is discussed. The best results in terms of enantioselectivity were obtained with <b>1c</b>-(<i>R;R</i>_<i>al</i><i>;R</i>), affording enantiomeric excesses up to 85% in both alkylation and amination reactions. A large match–mismatch effect between the absolute configurations of stereocenters of ligand <b>c</b> has been observed in the allylic amination process. Preliminary results in the rhodium-catalyzed asymmetric hydroformylation of styrene by using bis­(diamidophosphite) ligands <b>a</b>, <b>b</b>, and <b>c</b> disclosed in all cases low enantiomeric discrimination for the branched aldehyde. Both for the allylic alkylation and for the hydroformylation reaction, a related monodentate diamidophosphite <b>d</b>, derived from (<i>R</i>)-<i>N</i>,<i>N</i>′-dimethyl-1,1′-binaphthyldiamine and (<i>S</i>)-borneol, was also tested. Palladium complexes of this monodentate ligand showed fairly good enantioselectivity in allylic alkylation, but with very low rate, while the rhodium complex of <b>d</b> rendered better enantioselectivity (37% ee) than the bidentate ligands <b>a</b>–<b>c</b> in the hydroformylation of styrene