David J. Young

Functionalized 1,2,3-Triazoles as Building Blocks for Photoluminescent POLOs (Polymers of Oligomers) of Copper(I)

Two 3-D and one 2-D metal-organic frameworks [Cu(8)I(8)(L1)(4)](n) (1), [Cu(8)I(8)(L2)(4)](n) (2) and [Cu(4)I(4)(L3)(2)](n) ()3 were synthesized using three novel pyridine and pyrazole supported 1,2,3-triazoles, 1-(4-picolyl)-4-butyl-1H-1,2,3-triazole (L1), 1-(4-picolyl)-4-pentyl-1H-1,2,3-triazole (L2) and 1-(4-picolyl)-4-(3,5-dimethylpyrazolylmethyl)-1H-1,2,3-triazole (L3). In both complexes 1 and 2, there co-exist a 1-D Cu(I) oligomer and Cu(4) tetrahedron cluster in the 3-D polymeric structures. Complex 3 shows a 2-D (4, 4) net with the stair-step Cu(4)I(4) as node and L3 as a building block. All three complexes exhibit photoluminescence.

The First Two Cantharidin Analogues Displaying PP1 Selectivity

High pressure Diels-Alder reactions of furan and dimethylmaleate, and thiophene and maleimide resulted in two cantharidin analogues, 3 and 6 possessing PP1 selectivity (>40- and >30-fold selectivity) over PP2A. Both compounds exhibited moderate PP1 activity, 3 IC(50) 50 microM and 6 IC(50) 12.5 microM. Interestingly, the corresponding mono-ester derivatives of 3 showed no such selectivity.

Nitrogen-rich azoles as ligand spacers in coordination polymers.

N-heterocycle-based ligands are versatile building-blocks for coordination oligomer and polymer assemblies of first-row transition metals. Herein, we review recent developments in the design and synthesis of some nitrogen-rich azole-based ligands, their assembly modes in coordination oligomers and polymers, and the potential applications of the resulting metallosupramolecules.

Zinc, cobalt and copper coordination polymers with different structural motifs from picolyl-triazole hybrid ligands

A series of one-dimensional coordination polymers, viz. [ZnCl2L1]n (1a: 1a-I and 1a-II), [ZnCl2L2]n (1b), [ZnCl2L3]n (1c), {[Co(L1)2(OH2)2]·(ClO4)2·(H2O)2}n (2a), {[Co(L2)2(OH2)2]·(ClO4)2·(H2O)2}n (2b), {[Cu(L1)2(OH2)2]·(ClO4)2·(H2O)2}n (3a), {[Cu(L2)2(OH2)]·(ClO4)2·(H2O)·(MeOH)}n (3b), and {[Cu(L3)2(OH2)]·(ClO4)2·(H2O)2}n (3c), and a three-dimensional coordination polymer [Cu2I2L3]n (4c) have been synthesized by self-assembly of 4-picolyl substituted 1,2,3-triazoles, viz.1-(4-picolyl)-4-butyl-1H-1,2,3-triazole (L1), 1-(4-picolyl)-4-pentyl-1H-1,2,3-triazole (L2) and 1-(4-picolyl)-4-hexyl-1H-1,2,3-triazole (L3), with appropriate metal salts. These coordination polymers have been characterized by single-crystal and powder X-ray diffraction (XRD) and thermogravimetric analyses (TGA). Complexes 3a–c have been subject to EPR analysis. Complexes 1a–c are 1D coordination polymers formed by singly bridging L1–L3 using their picolyl and 3-positioned nitrogen. Their modes of propagation (zig-zag, helical and wave-like) vary with the length of the alkyl pendant at the 4-position on the triazole moiety. Centro-symmetric polymers 2a and 2b are formed by doubly bridging spacers as 1D chains of 18-membered metallocycles fused at octahedral Co(II) centers with coordinated aqua ligands with extensive water–ClO4− H-bonding. Cu(II) complex 3a (space groupP21/n) is isostructural with 2a, but 3b and 3c crystallize with a chiral space group (P21) with square pyramidal Cu(II) doubly bridged by L2 and L3 to give 1D macrocyclic chiral chains. The spacer in 4c shows uniquely high coordination ability by engaging the donor functions of the nitrogen, not only at the picolyl and 3-position but also at the 2-position of the triazole. The resultant 3D polymer network is neutral and solvate free and has higher symmetry (space groupI41/a) than 4a and 4b. The spontaneous resolution of 3b and 3c is traced to the configurational characteristics of the four ligands and its transfer to the crystal network through space chiral packing. The 1D coordination polymers 1 are thermally most stable, whereas the MeOH-solvated and hydrated perchlorate salt 3b decomposes violently upon heating. Variable temperature photoluminescence (VT-PL) measurements revealed strong low energy (LE) rt emissions for 4a and 4b but not for 4c. The high energy (HE) emissions of 4a–c however increase significantly as temperature decreases. The remarkable variety of structural motifs in these coordination polymers is the result of (a) flexible bonding modes of the picolyl–triazole hybrid ligands, (b) different metal geometry options, (c) halide participation as bridging or capping ligands, (d) possibility of hydrate or solvate coordination and (e) extensive H-bonding involving anionic perchlorate methanol solvate as well as hydrates that are coordinated directly (viz. primary) and indirectly (viz. secondary) to the metal.

Functional group reductions with Lewis base adducts of gallane

Abstract Tertiary amine and tertiary phosphine adducts of gallane, L·GaH3 (L = Me3N, quinuclidine, (C6H11)3P), reduce a variety of unsaturated functional groups with a selectivity different to that observed for similar alane adducts.

Chiral capillary electrophoresis with cationic pyrrolidinium‐β‐cyclodextrin derivatives as chiral selectors

New single-isomer, cationic beta-cyclodextrins, including mono-6-deoxy-6-pyrrolidine-beta-cyclodextrin chloride (pyCDCl), mono-6-deoxy-6-(N-methyl-pyrrolidine)-beta-cyclodextrin chloride (N-CH(3)-pyCDCl), mono-6-deoxy-6-(N-(2-hydroxyethyl)-pyrrolidine)-beta-cyclodextrin chloride (N-EtOH-pyCDCl), mono-6-deoxy-6-(2-hydroxymethyl-pyrrolidine)-beta-cyclodextrin chloride (2-MeOH-pyCDCl) were synthesized and used as chiral selectors in capillary electrophoresis for the enantioseparation of carboxylic and hydroxycarboxylic acids and dansyl amino acids. The unsubstituted pyCDCl exhibited the greatest resolving ability. Most analytes were resolved over a wide range of pH from 6.0 to 9.0 with this chiral selector. In general, increasing pH led to a decrease in resolution. The effective mobilities of all the analytes were found to decrease with increasing CD concentration. The optimal concentration for most carboxylic acids and dansyl amino acid was in the range 5-7.5 mM and >15 mM for hydroxycarboxylic acids. (1)H NMR experiments provided direct evidence of inclusion in the CD cavity.

Monodispersed submicron porous silica particles functionalized with CD derivatives for chiral CEC

Rapid and efficient enantioseparation of halogen aryl alcohols and β‐blockers propranolol and pindolol in packed bed CEC (p‐CEC) using as‐prepared submicron porous silica chiral stationary phases (CSPs) has been achieved. Monodispersed 0.66 and 0.81 μm chiral submicron porous silica spheres were prepared using tetramethoxysilane and hexadecyltrimethylammonium bromide, followed by a hydrothermal treatment method with ammonia–ethanol to expand the pore of silica spheres without changing their spherical morphology. A proper specific surface of ca. 230 m2/g and pore sizes average of 6–8 nm were obtained by this method. The submicron porous silica spheres were modified with mono‐6‐phenylcarbamoylated β‐CD via thiol‐en radical addition. They were packed into 9 cm 50 μm id capillary columns with photopolymerized monolithic frits. These submicron CSPs showed greater column efficiency (about 476  000 plates/m for 4‐iodophenyl‐1‐ethanol) and higher resolution than the corresponding 3 μm CSP.

The solvent promoted addition of tetraallyltin to aldehydes: A convenient and chemoselective allylation procedure

Aldehydes 2a – e react with tetraallyltin (1,0.25 equiv.) in methanol or other polar solvent at room temperature (ca 30°C, <20 h) to provide the corresponding homoallyl alcohols 3a – e in 69 – 98% yield. No additional catalysis is required.

Quinolines as chemotherapeutic agents for leishmaniasis

The development of leishmanicidal quinolines and their in vitro (promastigote and amastigote) and, where applicable, in vivo activities are reviewed. This survey provides a direct comparison of bioactivity across different species(e.g. L. donovani, L. amazonensis, L. chagasi, L infantum), and in different animal models (e.g. L. donovani Balb/c mice and L. donovani infected hamsters). The progress of selected quinolines through pre-clinical development and phase I/II trials, and the lead quinoline drugs sitamaquinine and Imiquimod, are discussed in conjunction with delivery systems and combination therapies.

Tetraallylstannane and Weinreb amides: a simple ‘green’ route to N-protected homoallylic alcohols and allyl ketones

Abstract We have explored the addition of tetraallylstannane ( 7 ) to a variety of N -protected Weinreb amides ( N -phthalimido and N -benzyl). Reactions were conducted in methanol and the ionic liquid, butylmethylimidazole tetrafluoroborate (bmim[BF 4 ]), yields of the corresponding N -protected allylketones were moderate to good. Allylation of the corresponding aminoaldehydes gave excellent yields of homoallylic alcohols (68–94%) and moderate to good diastereoselectivities (50–86%).