Easy separation of Δ and Λ isomers of highly luminescent [Ir(III)]-cyclometalated complexes based on chiral phenol-oxazoline ancillary ligands

A new class of neutral cyclometalated iridium(III) complexes with enantiomerically pure C(1)-symmetric phenol-oxazolines (3a,b) have been synthetized in high yields and fully characterized. Resolution of the corresponding Δ(R) and Λ(R) or Δ(S) and Λ(S) isomers was easily achieved by conventional flash chromatography. The corresponding Δ and Λ helicities have been confirmed by CD spectroscopy and X-ray crystallography. Regarding the absorption and luminescence properties with unpolarized light, no significant difference between Δ and Λ isomers has been observed. A strong blue luminescence is observed for deaerated solutions of complexes 5a and 5b in CH(3)CN.     

Purine nucleosides XVII. The synthesis and conformation of 6-amino-9-β-D-ribopyranosylpurine and related derivatives prepared via the fusion procedure

The preparation of 2, 6-dichloro-9-(2′,3′,4′-tri-O-acetyl-β-D-ribopyranosyl)purine (I) has been accomplished utilizing the acid catalyzed fusion procedure. The displacement of the 6-chloro group, or the 2- and 6-chloro group has been studied. Several new 6-substituted-9-(β-D-ribopyranosyl)purines have been prepared by catalytic dehalogenation of the corresponding 2-chloropurine nucleosides. The conformation and configuration of these D-ribopyranosylpurines has been assigned with the assistance of proton magnetic resonance studies.     

A new access to polyhydroxy piperidines of the azasugar class: synthesis and glycosidase inhibition studies

A new synthetic strategy has been devised to access a variety of polyhydroxylated piperidines belonging to the azasugar class of glycosidase inhibitors. The key precursor (3aR, 7aR)-5-benzyl-2,2-dimethyl-7-methylenehexahydro[1,3]dioxo[4,5-c]pyridine is obtained by photoinduced electron transfer (PET) cyclization of the corresponding alpha-trimethylsilylmethylamine radical cation to the tethered acetylene functionality. The new molecules have been evaluated for inhibitory properties for certain beta-glycosidases and have been found to be moderate to weak inhibitors of the enzymes under study.     

Asymmetric synthesis of (R)-reticuline. A new strategy for the asymmetric synthesis of isoquinolines via enantioselective epoxidation or dihydroxylation

A new strategy for the asymmetric synthesis of 1-benzyl-1,2,3,4-tetrahydroisoquinolines7 − 9 has been developed. The route involves introduction of asymmetry via enantioselective epoxidation or dihydroxylafion of corresponding stilbene precursors followed by aminolysis and Pomeranz-Fritsch cyclization. The strategy has been successfully applied to the asymmetric synthesis of (R)-reticuline (9), the key-intermediate in the synthesis of morphine alkaloids on the biomimetic route.     

Organocatalyzed asymmetric Michael reaction of β-aryl-α-ketophosphonates and nitroalkenes

The first enantioselective Michael reaction of β-aryl-α-ketophosphonates and nitroalkenes has been realized by using a new bifunctional Takemoto-type thiourea catalyst. The primary Michael adducts obtained were converted in situ to the corresponding amides through the aminolysis. High yields, excellent diastereoselectivities (>95:5 dr), and good enantioselectivities (up to 81% ee) have been achieved for the corresponding α,β-disubstituted γ-nitroamides. This reaction again demonstrated that α-ketophosphonates are interesting pronucleophiles that can be used as amide surrogates in organocatalyzed reactions.     

Introduction of functional groups into some chlorofluorocarbon ethers.

The electrochemical fluorination of 2-methyloxane, oxepane, 2-chloromethyloxane and 2-chloromethyloxolane has been carried out. The corresponding perfluoro(2-methyloxane) and perrfluorooxepane were obtained in fair yields from the first two compounds, but from the later two, the corresponding chlorine-containing perfluorocyclic ethers, i.e. perfluoro(2-chloromethyloxane) and perfluoro(2-chloromethyloxolane), were obtained only in small yields, respectively. These new compounds have been characterized by elemental analysis, and infrared, mass and ¹⁹F nmr spectra.     

A new titanium building block for early-late heterometallic complexes; preparation of a new tetrameric metallomacrocycle by self assembly

The new titanium dicarboxylate complex Cp*TiMe(OOC)2py (2) [Cp*=eta5-C5Me5; (OOC)2py = 2,6-pyridinedicarboxylate] has been synthesized. The reaction of complex 2 with water renders [Cp*Ti(OOC)2py]2O (3). The molecular structure of 3 has been studied by X-ray diffraction methods. Complex 2 reacts with isocyanides to yield the respective iminoacyl derivatives Cp*Ti(eta2-MeCNR)(OOC)2py [R=tBu (4), 2,6-dimethylphenyl (xylyl) (5)]. The molecular structure of complex4 has been established by X-ray diffraction. Compound 2 has been employed as a new building block for the preparation of new early-late heterometallic compounds; it reacts with [M(mu-OH)(COD)]2 (M = Rh, Ir) to give the corresponding tetranuclear metallomacrocycle derivatives [Cp*Ti{(OOC)(2)py}(mu-O)M(COD)]2 [M = Rh (6); Ir (7)]. The molecular structure of 6 has been established by X-ray diffraction.     

Reaction of bare VO+ and FeO+ with ammonia: a theoretical point of view

The potential energy surfaces corresponding to the dehydration reaction of NH(3) by VO(+) ((3)Sigma, (1)Delta, (5)Sigma) and FeO(+) ((6)Sigma, (4)Delta) metal oxide cations have been investigated within the framework of the density functional theory in its B3LYP formulation and by employing new optimized basis sets for iron and vanadium. The reaction is proposed to occur through two hydrogen shifts from the nitrogen to the oxygen atom giving rise to multicentered transition states. Possible spin crossing between surfaces at different spin multiplicities has been considered. The energy profiles are compared with the corresponding ones for the insertion of bare cations to investigate the influence on reactivity of the presence of the oxygen ligand. The topological analysis of the gradient field of the electron localization function has been used to characterize the nature of the bonds for all the minima and transition states along the paths.     

Palladium(0) nanoparticles stabilized by phosphorus dendrimers containing coordinating 15-membered triolefinic macrocycles in periphery

A new family of phosphorus dendrimers containing on their surfaces 3, 6, 12, and 96 15-membered azamacrocycles has been synthesized. The coordinating ability of these macrocycles to palladium(0) atoms allowed the preparation of new dendrimers of several generations containing the corresponding metal complexes and several new nanoparticulated materials, where nanoparticles are stabilized mainly by the complexed dendrimers of the zero, first, and fourth generations. No reduction process of palladium(II) salts was needed to prepare nanoparticles of 2.5-7.9 nm diameter. All the new compounds and materials have been characterized by NMR, IR, elemental analysis and/or matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) spectrometry, high-resolution transmission electron microscopy, and electron diffraction. Also UV-vis spectra were obtained. The Mizoroki-Heck reaction has been catalyzed in a homogeneous and heterogeneous manner by using four different materials; in all cases, the catalyst could be recovered and reused several times.     

One-pot synthesis of meso-formylporphyrins by S(N)Ar reaction of 5,15-disubstituted porphyrins with (2-pyridyldimethylsilyl)methyllithium

A simple, one-pot procedure that converts 5,15-substituted porphyrins into the corresponding meso-formylated porphyrins has been developed. The method, based on a new synthetic concept for functionalized porphyrins utilizing the (2-pyridyldimethylsilyl)methyl group as a latent formyl functionality, affords the desired product in good yield and is especially appropriate for the direct formylation of free base porphyrins, which has never been achieved by known methods.     

三元体系Sm(NO~3)~3-ACAP-H~2O相平衡研究及Sm(ACAP)~2(NO~3)~3的合成和表征

在30℃时采用等温溶度法研究了三元体系Sm(NO~3)~ 3- ACAP- H~ 2OACAP, 4-acetylantipyrine,4-乙铣基安替比林)的相平衡,绘制了体系的溶度图及饱和溶液的折光率一组成图,发现并制备了未见文献报道的同成分溶解的化合物Sm(ACAP)~2(NO~3)~3,通过化学分析,元素分析,摩尔电导(DMF),IR和TG-DTG 对其进行了物理化学性质表征,初步探讨了阴离子对ACAP与稀土相互作用的影响.     

Facile Synthesis of Chiral Conjugated Polymer Based on BINOL Skeleton

The study of polymer supported chiral catalysts has attracted very extensive attention inrecent years'. The intrinsic advantages of these catalysts in organic synthetic chemistryare that they can be separated with the products by simple filtration. Traditionally,polymer chiral catalysts are prepared by allaching chiral ligand to sterically irregularpolymer backbone2. In this system, the catalytic sites are randomly oriented along thepolymer chain which makes it very difficult to systematically…     

Hydrogenation of aldehydes catalyzed by kieselguhr‐supported carboxymethylcellulose‐nickel complex

A new kieselguhr‐supported carboxymethylcellulose‐nickel complex (Kie‐CMC‐Ni) has been prepared by a simple method, which has been found to catalyze the hydrogenation of benzaldehyde, valeraldehyde and isobutyraldehyde to the corresponding alcohols in high yield (100, 92 and 86% respectively). The catalyst could be reused without obvious loss of its catalytic activity. Copyright © 2004 John Wiley & Sons, Ltd.     

Stereoselective formal synthesis of (−)-mesembrane by intramolecular condensation of chiral amide and 1,3-cyclohexanedione moiety

A new stereoselective formal synthesis of (−)-mesembrane has been achieved by intramolecular condensation of chiral amide and 1,3-cyclohexanedione moiety. The precursor amide was readily prepared by condensation of the corresponding chiral amine and acid. Condensation provided moderate ratios of ene-amide derivatives and the following transformation of functional groups has yielded the known precursor for (−)-mesembrane, resulting in formal synthesis.     

Elucidation of the Electrochemical Oxidation Pathway of Ammonia in Dimethylformamide and the Room Temperature Ionic Liquid, 1‐Ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide

The direct electrochemical oxidation of ammonia has been examined in both the organic solvent dimethylformamide (DMF) and the room temperature ionic liquid 1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIM][N(Tf)₂]. The corresponding voltammetric responses have been shown to be similar in each solvent with a broad oxidative wave occurring upon the introduction of ammonia to the solution and the appearance of a new reductive wave following the oxidation. The oxidative reaction process has been examined and a suitable reaction pathway has been deduced, corresponding to the formation of ammonium cations after oxidation of the ammonia. A linear response of limiting current against vol% ammonia was observed in both DMF and [EMIM][N(Tf)₂], suggesting potential application for analytical methods.     

Synthesis and spectroscopy of phosphonate derivatives of uracil and thymine. X-ray crystal structure of diethyl 6-uracilmethylphosphonate

A new class of phosphonate ligands, derived from uracil and thymine was designed, prepared and characterised. Dimethyl ( 4, 7 ) and diethyl ( 5, 8 ) uracilmethylphosphonates have been prepared by the reaction of chloromethyluracil isomers 2 and 3 with trimethyl phosphite and triethyl phosphite, respectively. The corresponding free acids, 5-uracilmethylphosphonic acid 6 and 6-uracilmethylphosphonic acid 9 , have also been isolated. The structure of the compounds has been assigned by nmr spectroscopy and, in the case of 8 , confirmed by X-ray analysis.     

Contribution à la phytochimie du genre Gentiana I. Etude des composés flavoniques et xanthoniques dans les feuilles de Gentiana lutea L. (1re communication)

Six polyphenolheterosides have been isolated from the leaves of G. lutea L. by means of thin layer and column chromatography on polyamide. The xanthones mangiferin (III) and gentioside (IV), the flavones isoorientin (V) isovitexin (VI) and two new heterosides (E and F) have been isolated. E gave isoorientin and glucose on hydrolysis and F isovitexin, glucose and gentiobiose. Structure identification has been achieved by UV., IR. and NMR. spectroscopy as well as by synthesis of the corresponding aglycones.     

Reversed phase extraction chromatographic separation of ruthenium(III)

A new an innovative separation method has been developed using N-n-octylaniline (liquid anion exchanger) coated on silica gel. Ruthenium(III) has been extracted quantitatively from 0.05 M hydrochloric acid, striped with aqueous solution of various acids and then determined by spectrophotometric method. Mutual separation scheme for ruthenium(III), iridium(III) and osmium(VIII) has been developed. Ruthenium(III) has been separated from commonly associated elements. Different parameter are studied viz effect of acid concentration, reagent concentration, striping agent, flow rate, foreign ion and synthetic mixture corresponding to alloys. Validity of method has been verified by separation of ruthenium(III) from fissium alloy.     

1,2-HOIQO--a highly versatile 1,2-HOPO analogue

A cyclic, bidentate hydroxamic acid binding unit based on an isoquinoline scaffold has been utilized for the synthesis of a hexadentate tripodal ligand based on the TREN backbone. This prototype for a new class of multidentate chelators forms mononuclear iron(III) complexes and one-dimensional coordination polymers with lanthanide(III) cations. The latter has been determined by single-crystal X-ray analysis of the cerium species. The solid-state structure in the monoclinic space group P2(1)/c (C(36)H(34)CeN(7)O(11), a = 12.341(2) A, b = 26.649(4) A, c = 10.621(2) A, alpha = gamma = 90 degrees, beta = 96.753(3) degrees, V = 3468.6(9) A3, Z = 4) exhibits a trigonal-dodecahedral environment around the cerium cation. The proof of concept for the versatility of the new scaffold has been shown by the modification of the crucial precursor 3-carboxyisocoumarin through electrophilic aromatic substitutions to yield the corresponding chlorosulfonated and nitrated analogues.     

Selective oxidation of sulfides and oxidative bromination of organic substrates catalyzed by polymer anchored Cu(II) complex

A new polymer-anchored Cu(II) complex has been synthesized and characterized. The catalytic performance of the complex has been tested for the oxidation of sulfides and in oxidative bromination reaction with hydrogen peroxide as the oxidant. Sulfides have been selectively oxidized to the corresponding sulfoxides in excellent yields and in the presence of KBr as the bromine source, organic substrates have been selectively converted to mono bromo substituted compounds using polymer-anchored Cu(II) catalyst. This catalyst showed excellent catalytic activity, high selectivity, and recyclability. The polymer-anchored Cu(II) catalyst could be easily recovered by filtration and reused more than five times without appreciable loss of its initial activity.