J. L. Arias

Perspectives of antimony compounds in oncology

AbstractAntimony, a natural element that has been used as a drug for over more than 100 years, has remarkable therapeutic efficacy in patients with acute promyelocytic leukemia. This review focuses on recent advances in developing antimony anticancer agents with an emphasis on antimony coordination complexes, Sb (III) and Sb (V). These complexes, which include many organometallic complexes, may provide a broader spectrum of antitumoral activity. They were compared with classical platinum anticancer drugs. The review covers the literature data published up to 2007. A number of antimonials with different antitumoral activities are known and have diverse applications, even though little research has been done on their possibilities. It might be feasible to develop more specific and effective inhibitors for phosphatase-targeted, anticancer therapeutics through the screening of sodium stibogluconate (SSG) and potassium antimonyltartrate-related compounds, which are comprised of antimony conjugated to different organic moieties. For example, SSG appears to be a better inhibitor than suramin which is a compound known for its antineoplastic activity against several types of cancers.

Trans Influence of Triphenylstibine: Crystal Structures of cis‐[PtBr2(SbPh3)2], trans‐[PtBr(Ph)(SbPh3)2], [NMe4][PtBr3(SbPh3)], and cis‐[PtBr2(SbPh3)(PPh3)]

The work reports the unexpected reaction of diphenyldibromo antimonates (III) with PtCl2 and cis-[PtCl2(PPh3)2]. The reaction gives triphenylstibine containing PtII complexes viz. cis-[PtBr2(SbPh3)2] (1), trans-[[PtBr(Ph)(SbPh3)2] (2), [NMe4][PtBr3(SbPh3)] (3), and cis-[PtBr2(PPh3)(SbPh3)] (4). All the complexes were characterised by elemental analyses, IR, Raman, 195Pt NMR, FAB mass spectroscopy and X-ray crystallography. A plausible mechanism via the phenyl migration is proposed for the formation of these complexes. The average Pt–Br distance in 1 is 2.456(2) A, in 2 2.496 A(trans to Ph) while in 3 it is 2.476 A (trans to Sb) implying a comparable trans influence of Ph3Sb and Ph3P. Transeinflus von Triphenylantimon: Die Kristallstrukturen von cis-[PtBr2(SbPh3)2], trans-[PtBr(Ph)(SbPh3)2], [NMe4][PtBr3(SbPh3)] und cis-[PtBr2(SbPh3)(PPh3)] Es wird uber die unerwartete Reaktion von [Ph2SbBr2]– mit PtCl2 und cis-[PtCl2(PPh3)2] berichtet, die die Platin(II)-Komplexe cis-[PtBr2(SbPh3)2] (1), trans-[[PtBr(Ph)(SbPh3)2] (2), [NMe4][PtBr3(SbPh3)] (3) und cis-[PtBr2(PPh3)(SbPh3)] (4) ergibt. Die Komplexe werden durch Elementaranalyse, IR, Raman, 195Pt-NMR, FAB-Massenspektrometrie und Rontgenstrukturanalyse charakterisiert. Fur die Bildung der Komplexe wird ein Reaktionsmechanismus durch Ligandenaustausch vorgeschlagen. Der mittlere Pt–Br-Abstand betragt in 1: 2,456 A, in 2: 2,496 A (trans zu Ph), in 3: 2,476 A (trans zu Sb), was auf einen ahnlichen Transeinflus von Ph3Sb und Ph3P hinweist.

1,3-dioxolane formation with a montmorillonite-type clay catalyst

Abstract The coupling reaction of oxiranes with carbonyl compounds to produce 1,3-dioxolanes was promoted by catalytic amounts of a bentonitic clay. The product yield was found to be dependent on the catalyst, the reaction temperature and the reagent concentrations. A kinetic study performed with acetone and ethylene oxide showed a first-order dependence in both reagents. Other experiments made with different epoxides, carbonyl compounds and catalysts are also discussed.

Catalytic hydrocyanation of α-ketoalkynes by Ni(CN)2/CO/KCN system in alkaline aqueous media: Identification of the active species

Abstract 5-Hydroxy-3-pyrrolin-2-ones are regioselectively synthesized in a good yield under very mild conditions by tetracyanonickelate (0) ion catalyzed hydrocyanation of α-ketoalkynes, in the absence of hydrogen cyanide. The catalyst is prepared in situ in a basic aqueous medium by reduction of Ni(CN) 2 with CO in the excess of KCN. From the IR spectroscopy studies and by evaluation of catalytic activity of some cyanonickelates it is proposed that [Ni(CN) 4 ] −4 anion is the active species in the process. A possible mechanism is suggested for the conversion of nickel cyanide to [Ni(CN) 4 ] −4 . The effect of the reaction variables, e.g.: reaction time, temperature, absorption of carbon monoxide, the concentration of potassium cyanide, water, substrate, and sodium hydroxide were also examined.

Catalytic auto-condensation of 2,4-pentanedione promoted by Sm(III) acetylacetonate: the X-ray structure of a novel complex [Sm(CH3COO)3(H2O)2](H2O)2

Abstract An efficient one-pot catalytic method to obtain 4,6-dimethyl-2-hydroxyacetophenone (A) is reported, the reaction proceeds via the intermolecular auto-condensation of 2,4-pentanedione using samarium(III) acetylacetonate (Sm(AcAc)3) as promoter. A novel complex [Sm(CH3COO)3(H2O)2](H2O)2 (I) was isolated from the reaction media. The structure of I was determined by X-ray crystallography showing that the central atom is ennea-coordinated (monocapped square-antiprism geometry). This complex I also shows activity in the named autocondensation reaction.

STIBINE-MODIFIED WILKINSON'S CATALYST AND CO2(CO)8 CATALYST : HYDROFORMYLATION OF 1-PENTENE

Abstract The homogeneous hydroformylation of 1-pentene under synthesis gas experimental conditions was studied using Wilkinsons catalyst and Co2(CO)8 modified by different triarylstibines. The stibine ligands SbR3 (where R = 2,4,6-mesityl, p-tolyl and o-tolyl), have been tested with Wilkinsons catalyst and Co2(CO)8 These catalysts have also been studied separately with PPh3 for comparison, under the same hydroformylation conditions. It is interesting to note that 1:1 addition of these stibine ligands to the catalysts, extraordinarily increases the yields of aldehydes with appreciable n:iso ratio. The maximum yield of aldehydes obtained were 98.6% with n/iso = 2.4 when RhCl(PPh3)3 + trimesityl stibine system was used and 85.0% with n/iso = 3.4 when Co2(CO)8 + trimesityl stibine system was studied.

Hydrodimerization of Cyclic α, β Unsaturated Ketones Promoted by Samarium Iodide

Abstract An example of hydrodimerization of some cyclic enones by SmI2/THF system is described. The use of HMPA (hexamethyl phosphoramide), as a copromoter in the system, improves the yield of dimerized products. The X-ray structure of one of these dimers, bis-3,3′(3,5,5-trimethyl cyclohexanone), is also reported.

Characterization of a novel [Sm(HMPA)4I2]I complex by positive ion fast atom bombardment and high resolution mass spectrometry

Abstract A positive-ion Fast Atom Bombardment (FAB) study was performed to determine the structure of samarium(III) triiodine complex (I). Collision Induced Dissociation (CID) and High Resolution Mass Spectrometry were used to establish the fragmentation pattern of the C24H72O4N12P4I3Sm compound. The structure of (I) was confirmed by X-ray analysis.

The crystal structure of a novel complex [Sm(HMPA)3(H20)4]3+3[I−] formed in the reductive cyclodimerization of linear α,β-unsaturated ketones by SmI2

Abstract The samarium iodide/HMPA has been used to promote cyclodimerization of linear α,β-unsaturated ketones. A novel complex [Sm(HMPA) 3 (H 2 O) 4 ] 3+ 3[I − ] ( 1 ) was isolated from the reaction and its X-ray crystal structure was determined. The Sm ion is hepta-coordinated displaying a pentagonal bipyramid geometry and an extensive hydrogen-bond network which keeps together the molecules in the crystal.

Cyclo- and hydrodimerization of α,β-unsaturated ketones promoted by samarium diiodide

Samarium(II) iodide is a strong one-electron transfer reducing agent, and is effective for the cyclo- and hydrodimerization of cyclic and non-cyclic α,β-unsaturated ketones. The title dimers can easily be prepared in good yields at room temperature under neutral conditions, using two-mole equivalent of SmI2 per mole of starting substrate. The reaction is stereocontrolled. The absence of an alcohol as a proton source is essential in the process and the use of HMPA as a copromoter improves the yield of dimeric products, making the reaction regioselective over the competitive CC double bond reduction. The crystal structures of some of the dimeric derivatives are reported. When η2- or η4-iron-coordinated α,β-unsaturated ketones are used as substrates, the reaction gives mainly the 1,4-reduced products.