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The ordered double perovskites Ba2-xSrxYIrO6 (x = 0—2) are prepared by calcination of stoichiometric mixtures of BaCO3, SrCO3, Y2O3, and Ir in air (alumina crucible, staged heating at 650—850 °C, 12 h per stage) followed by staged sintering in air at 1050—1350 °C (72 h per stage).

Polycrystalline samples of Sr2BIrO6 (B: In, Sc, Fe, Co, Ti) are prepared from citrate precursors using stoichiometric mixtures of Sr(NO3)2, IrO2, In2O3, Sc2O3, FeC2O4, Co(NO3)2, and TiC10H14O5 in aqueous solutions of citric acid and HNO3 followed by heating of the resulting resins (600 °C, 12 h) and calcination in air (1100—1200 °C, 12 h).

Pd-catalyzed carbonylation of aryl bromides (I) in the presence of phosphonium chloride provides an efficient access to benzoic chlorides, which can be easily transformed into corresponding esters (IV) or hydrazides (V).

Polycrystalline Sr2CaIrO6 (I) and Sr2MgIrO6 (II) are prepared from citrate-nitrate precursors using Sr(NO3)2, IrO2, CaCO3, or MgO in aqueous citric acid and HNO3 evaporated at 140 °C and heated to 600 °C to decompose organic residues and NO3 (950 °C, 12 h, O2 pressure of 200 bar (I), 800 °C, 36 h for (II)).

Double perovskites containing Ir6+/Ir5+ with formula Sr2MIrO6 (M = Ni, Zn) have been synthesized under high oxygen pressure conditions. Their crystal structures have been studied by X-ray and neutron powder diffraction at room temperature (RT) and 2 K. At RT, these oxides crystallize in the monoclinic space group P21/n with unit-cell parameters a ≈ √2a0, b ≈ √2a0, and c ≈ 2a0, and β ≈ 90°. The thermal evolution of the structure of the Ni-containing compound shows the presence of two phase transition in the 373–673 K interval following the sequence P21/n → I4/m → Fm3m. These materials have also been characterized by magnetic measurements, suggesting the onset of antiferromagnetic interactions at TN = 58 and 46 K, for M = Ni, Zn, respectively. X-ray absorption spectroscopy sheds light on the oxidation states of M and Ir ions within these double perovskites.

The series of title compounds is prepared from citrate precursors at 3.5 GPa and 1000 °C (1 h) in the presence of KClO4.

Chiral didehydro amino acid esters 2 3 derived from amino acids are hydrogenated stereoselectively with rhodium catalysts based on achiral ligands, the α,γ-diamino acid derivatives 4 being the major products. The sense and degree of stereoselectivity can be influenced to some extent by the use of chiral diphosphines. The iridium-containing Crabtree-catalyst is particularly effective in the case of the serine derivative 2 (R1 = HOCH2).

Low temperature oxidations of selected higher order cyanocuprates composed of one or two heteroaromatic ligands can be oxidatively coupled in an inter- or intramolecular fashion to afford unsymmetrical biaryls. Non-heteroaromatic systems have also been studied in related intramolecular processes.

Treatment of lower order arylcyanocuprates ArCu(CN)Li with 1 equiv of an aryllithium (Ar'Li) at temperatures around -125 o C leads to higher order reagents Ar(Ar')Cu(CN)Li 2 . Upon exposure of such reagents at this temperature to ground-state molecular oxygen, good yields of the unsymmetrical biaryl Ar-Ar' can be realized. Several different types of aryl ligands have been examined, including naphthalenes, to assess the generality of this method. Spectroscopic data ( 13 C NMR) have been obtained on three different cuprates at -130 o C and at higher temperatures to determine if their kinetic nature, as illustrated by their synthetic chemistry, can be substantiated by physical means

An easy approach to the synthesis of substituted unsaturated lactones is described, and the reactions of these compounds with nucleophiles leading to the formation of useful intermediates are reported.

Generation of an intramolecularly tethered, nonracemic diaryl cuprate followed by its oxidation with ground state oxygen at −78° leads to a biaryl precursor to an ellagitannin. Subsequent attachment of the appropriate glucose unit completes the synthesis of the title compound.

The catalytic repertoire of baker's yeast has been expanded to include enantioselective Baeyer–Villiger oxidations. To create this catalyst, the Acinetobacter sp. cyclohexanone monooxygenase gene was inserted into a yeast expression vector and this was used to create a ‘designer yeast’ that performed oxidation reactions. Whole cell-mediated Baeyer–Villiger reactions were carried out on a 1.0 mmol scale and several cyclic ketones were converted in 20–30 h into the corresponding lactones in isolated yields of 60–83%. Under the reaction conditions, ketone reduction constituted only a minor side-reaction. Oxidation of prochiral 4-substituted cyclohexanones produced lactones with very high enantioselectivities.

This paper describes simple and successful methods for the preparation of stabilized halogenated phosphoylides and discusses their stability, reactivity, and utility in organic synthesis. Preparations of several halogenated compounds including pharmaceutically interesting enol lactones are reported. Keywords: halogenated stabilized ylides, preparation, structure, stability, reactivity, applications; vinylic halides, halo enol lactones.

Hydrolysis of the carcinogenic title compound 1a in 5 vol % CH3CN−H2O, μ = 0.5, 20 °C at pH 7.2 in 0.02 M phosphate buffer, yields the rearranged material 3-(sulfonatooxy)-N-acetyl-4-aminostilbene (4) (23 ± 1%), threo-1,2-dihydroxy-1-phenyl-2-(4-acetamidophenyl)ethane (5) (57 ± 2%), and erythro-1,2-dihydroxy-1-phenyl-2-(4-acetamidophenyl)ethane (6) (20 ± 2%) in the absence of added nucleophiles. Addition of N3- has no effect on the rate constant for decomposition of 1a (ca. 1.9 × 10-2 s-1), but generates a number of adducts that result from trapping of three different electrophilic intermediates. The ortho-N3 adduct 3-azido-N-acetyl-4-aminostilbene (7) is produced from trapping of the nitrenium ion 2. A fit of the product yield data as a function of [N3-] provides the ratio kaz/ks of 280 ± 10 M-1 for competitive trapping of 2 by N3- and H2O. The nucleophilic aromatic substitution product 7 is a minor reaction product. The predominant site of attack by N3- on 2 (ca. 85%) is at the β-vinyl carbon to produce...

Whole cells of an Escherichia coli strain that overexpresses Acinetobacter sp. NCIB 9871 cyclohexanone monooxygenase have been used for the Baeyer−Villiger oxidations of a variety of 4-mono- and 4,4-disubstituted cyclohexanones. In cases where comparisons were possible, this new biocatalytic reagent provided lactones with chemical yields and optical purities that were comparable to those obtained from the purified enzyme or a strain of bakers' yeast that expresses the same enzyme. The efficient production of cyclohexanone monooxygenase in the E. coli expression system (ca. 30% of total soluble protein) allowed these oxidations to reach completion in approximately half the time required for the engineered bakers' yeast strain. Surprisingly, 4,4-disubstituted cyclohexanones were also accepted by the enzyme, and the enantioselectivities of these oxidations could be rationalized by considering the conformational energies of bound substrates along with the enzyme's intrinsic enantioselectivity. The enzyme expr...

Cyclohexanone monooxygenase (CHMO) from Acinetobacter sp NCIMB 9871 expressed in baker's yeast and in E. coli and cyclopentanone monooxygenase (CPMO) from Comamonas (previously Pseudomonas) sp. NCI...

Commercially available, air- and water-stable naphthoquinone imidazolin-2-ylidene-palladium(0) complexes were found to be highly active one-component catalysts for the amination of aryl halides. With these very robust catalysts, the expensive bases Cs 2 CO 3 or NaOt-Bu traditionally used can be replaced by KOH. A convenient reaction protocol has been developed for the coupling of a wide range of aryl chlorides with primary or secondary amines.

The matrix isolation technique has been combined with theoretical calculations to identify and characterize the photoproducts in the reaction of PH3 with OVCl3 and CrCl2O2. In contrast to previous studies, HCl elimination from an initial complex is not observed. Instead, a number of product bands, some quite intense, were observed and have been assigned to phosphine oxide, H3PO, through the direct O atom transfer from the transition metal oxo compound. This identification was supported by extensive isotopic labeling, and by comparison to theoretical calculations. H3PO formed in this manner is cage-paired and interacts with the transition metal fragment (VCl3 or Cl2CrO), leading to a 113 cm-1 red-shift of the PO stretching mode relative to isolated monomeric H3PO.

Chiral β-N,N-dibenzylamino nitriles Bn 2 NCH(R)CH 2 CN, prepared in enantiomerically pure form from α-amino acids, can be deprotonated and stereoselectively alkylated to afford β-amino nitriles Bn 2 NCH(R)CH(R′)CN with two stereogenic centers. LiAlH 4 -reduction leads to the corresponding 1,3-diamines.