Daan van Leusen

Neutral versus cationic Group 3 metal alkyl catalysts: performance in intramolecular hydroamination/cyclisation

The relative catalytic activity of neutral dialkyl versus cationic monoalkyl Group 3 metal catalysts in the intramolecular hydroamination/cyclisation of the 2,2-dimethyl-4-pentenylamine reference substrate was investigated. This was found to depend strongly on the nature of the monoanionic ancillary ligand. With a bidentate amidinate ligand, the neutral catalysts were quite effective, but their cationic derivatives showed a much lower activity. The reaction kinetics suggest that this reflects an intrinsically higher activation barrier for the insertion of the olefinic moiety into the metal-amide bond for the cationic catalysts. In contrast, the neutral catalysts with tetradentate triamine-amide ligands showed a much lower activity than their cationic derivatives. It appears that this higher activity of the cationic triamine-amide catalysts reflects the beneficial effect of the additional available coordination space relative to the neutral species. The cationic triamine-amide yttrium catalysts are more active than the cationic amidinate catalysts of the same metal, possibly reflecting a stronger Y-amide bond in the latter, which is the more electron-deficient system.

An efficient synthesis of 3-nitropyrroles☆

3-Nitropyrroles are synthetically accessible in high yield from nitromethane and 1-isocyano-1-tosyl-1-alkenes (1), in one single operation.

Yttrium alkyl complexes with a sterically demanding benzamidinate ligand: synthesis, structure and catalytic ethene polymerisation

The benzamidinate yttrium dialkyl complexes [PhC(NAr)2]Y(CH2SiMe3)2(THF)n (Ar = 2,6-diisopropylphenyl; n = 1, 2) were prepared; when activated with [PhNMe2H][B(C6F5)4], the species with n = 1 polymerises ethene to polyethene with a narrow polydispersity.

Synthesis and characterization of the 6α- and 6β-hydroxylated derivatives of corticosterone, 11-dehydrocorticosterone, and 11-deoxycortisol

This report describes the synthesis of 6alpha,17,21- and 6beta,17,21-trihydroxypregn-4-ene-3,20-dione, 6alpha,7,21- and 6beta,11beta,21-trihydroxypregn-4-ene-3,20-dione, and-for the first time-that of 6alpha,21- and 6beta,21-dihydroxypregn-4-ene-3,11,20-trione. The former four compounds were prepared by 6-hydroxylation of 17,21-trihydroxypregn-4-ene-3,20-dione and 11beta,21-dihydroxypregn-4-ene-3,20-dione, respectively. This was achieved by autoxidation or by oxidation with 3-chloroperbenzoic acid, of the 3-methoxy-pregna-3,5-dienes of the latter two steroids. The yield of the 6beta-hydroxylated steroids, but not of their corresponding 6alpha-epimers, was higher using autoxidation than the peracid. The two 6-hydroxylated pregnenetriones were prepared from 6alpha,21-diacetoxy-11beta-hydroxypregn-4-ene-3,20-dione and 6beta,21-diacetoxy-11beta-hydroxypregn-4-ene-3,20-dione, respectively, by oxidation with pyridinium chlorochromate. The above-mentioned six steroids were identified and characterized by nuclear magnetic resonance, infrared, ultraviolet, high performance liquid chromatography, gas chromatography, and mass spectrometry.

Synthesis of 2-Acyladamantanes

Abstract Few 2-acyl derivatives of adamantane have been reported unlike the isomeric 1-acyladamantanes of which a whole series is known.1 In connection with a study of 1-isocyano-1-tosylmethyl-ideneadamantane2 we have developed a useful high yield route to 2-acyladamantanes (4) starting from 2-cyanoadamantane (1). The latter compound has become readily available recently in a one-pot synthesis from adamantanone.3

Neutral and cationic yttrium alkyl complexes with linked 1,4,7-triazacyclononane-amide monoanionic ancillary ligands: synthesis and catalytic ethene polymerisationElectronic supplementary information (ESI) available: experimental, spectroscopic and polymerization details. See http://www.rsc.org/suppdata/cc/b1/b101012n/Netherlands Institute for Catalysis Research (NIOK) publication no. RUG 01-4-01.

Yttrium dialkyl complexes [N,N′-R2-tacn-N″-(CH 2)2NBut]Y(CH2SiMe3) 2 (R = Me, Pri; tacn = 1,4,7-triazacyclononane) were prepared; when activated with [PhNMe2H][B(C6F5)4] these complexes form cationic alkyl species that are active ethene polymerisation catalysts.