Formation of LiAlyNi1−yO2 solid solutions under high and atmospheric pressure

Three methods were used for the synthesis of LiAl_yNi_1−yO₂ solid solutions with layered crystal structure: citrate and hydroxide precursor methods at atmospheric pressure and high-pressure synthesis in oxygen-rich atmosphere (3 GPa). Structural characterization of the oxides was performed by powder XRD analysis and electron paramagnetic resonance (EPR) spectroscopy. Irrespective of the different preparation techniques used, it was found that LiAl_yNi_1−yO₂ solid solutions can be formed in the limited concentration range of 0?y?0.5 and 0.75?y?1.0. The unit cell parameter a decreases linearly with the Al content whereas the unit cell parameter c increases sharper as compared to the linear interpolation of the c parameter calculated for the two end compositions LiNiO₂ and LiAlO₂. In these compositions, aluminum substitutes for Ni in the NiO₂-layer, the mean Al_yNi_1−y-O bond length decreasing. The extent of the trigonal distortion of Al_yNi_1−yO₆ and LiO₆-octahedra varies with the aluminum content and depends on the synthesis procedure used. The LiO₆-octahedra are more flexible to tolerate the increased trigonal distortion as compared to the Al_yNi_1−yO₆-octahedra. High-pressure synthesis favors the formation of oxides with a higher extent of trigonal distortion of both Al_yNi_1−yO₆ and LiO₆-octahedra. From EPR measurements, it was shown that local cationic distribution in LiAl_yNi_1−yO₂ depends on the synthesis temperature. At atmospheric pressure, higher synthesis temperatures promote the reaction of cation mixing between the layers.     

Synthesis of methyl (5Z,8Z,10E,12E,14Z)-eicosapentaenoate

The first total synthesis of methyl (5Z,8Z,10E,12E,14Z)-eicosapentaenoate has been achieved in seven steps and in 16% overall yield. The synthesis confirmed the assigned structure of this polyunsaturated natural product.     

1,9-Bis(N,N-dimethylaminomethyl)dipyrromethanes in the synthesis of porphyrins bearing one or two meso substituents

A synthesis of 5,15-disubstituted zinc-porphyrins has been developed that employs condensation of a 1,9-bis(N,N-dimethylaminomethyl)dipyrromethane+a dipyrromethane in refluxing ethanol containing zinc acetate followed by oxidation with DDQ. The N,N-dimethylaminomethylation of the dipyrromethane was achieved via Eschenmoser's reagent (N,N-dimethylmethyleneammonium iodide) in CH₂Cl₂ at room temperature. The synthesis is compatible with diverse substituents (e.g., alkyl, aryl, ester, acetal) and enables rapid synthesis of trans-AB-, A₂-, and A-porphyrins. The synthesis of >40 zinc porphyrins has been surveyed; 13 zinc porphyrins were isolated in yields of 5-20% without detectable scrambling.     

Mild and practical stereoselective synthesis of (Z)- and (E)-allyl bromides from Baylis-Hillman adducts using Appel agents (PPh3/CBr4): a facile synthesis of semiplenamides C and E

Appel agents (PPh₃/CBr₄) have been utilized for high-yielding stereoselective synthesis of (Z)- and (E)-allyl bromides from Baylis-Hillman adducts at room temperature. The method has been applied for the synthesis of naturally occurring bioactive fatty acid amides, semiplenamides C and E.     

1,n-Diamines. Part 3: Microwave-assisted synthesis of N-acyl-N′-arylhexahydropyrimidines and hexahydro-1,3-diazepines

In this Letter we present a method for the synthesis of N-acyl-N′-arylhexahydropyrimidines 1, by ring closure of N-acyl-N′-aryl-1,3-propanediamines 3 with formaldehyde. Cyclodehydrations were performed in aqueous medium under microwave irradiation, and led to high yields of the desired compounds in remarkably short reaction times. The method also allowed for the synthesis of hitherto unreported N-acyl-N′-arylhexahydro-1,3-diazepines 2. The acyclic tetramethylenic precursors 4 were synthesized by selective functionalization of N-arylputrescines.     

An efficient synthesis of N-Boc-(2S,3S)-3-hydroxy-2-phenyl piperidine and N-Boc-safingol

An efficient strategy has been developed for the stereo selective synthesis of N-Boc-(2S,3S)-3-hydroxy-2-phenyl piperidine and N-Boc-safingol from benzaldehyde and N-Boc-imine.     

Synthesis of meso-tetraarylporphyrins using SeO2 as oxidant

The oxidative step of the two-step, one-flask synthesis of meso-tetraarylporphyrins is herein conducted with heterogeneous oxidant SeO₂ instead of the usual quinones DDQ or p-chloranil. Evaluation of BF₃O(Et)₂ or I₂ amount for the condensation of the first step combined with the excess of SeO₂ defined porphyrin synthesis conditions employing benzaldehydes and pyrrole (or 5-phenyldipyrromethane) as starting materials. The simplicity of the workup, allied with reaction mild conditions, makes this method a good option for the synthesis of this kind of compound.     

Synthesis of Δ-15-deoxy-PG-J1 methyl ester and epi-Δ-15-deoxy-PG-J1

The synthesis of racemic Δ^12,14-15-deoxy-PG-J₁ is readily achieved in six steps employing as the key transformation a one-pot conjugate addition-Peterson olefination sequence using exo-2-trimethylsilyl-3a,4,7,7a-tetrahydro-4,7-methanoinden-1-one. Additionally a Noyori-type three-component coupling approach is employed for the synthesis of enantioenriched epi-Δ¹²-15-deoxy-PG-J₁ from 4(S)-tert-butyldimethylsilyloxycyclopent-2-enone.     

Synthesis of meso-tetraphenyl porphyrins via condensation of dipyrromethanes with N-tosyl imines

A new synthetic route for the synthesis of 5,10,15,20-tetraphenyl porphyrins has been developed based on the reaction of 5-substituted dipyrromethanes with N-tosyl imines in the presence of a metal triflate catalyst. meso-Substituted tetraphenyl porphyrins were synthesized in a two-step process. The first step of the method is the metal triflate-catalyzed condensation of 5-substituted dipyrromethanes with N-tosyl imines to form a porphyrinogen intermediate and the second step is the oxidation of the porphyrinogen to porphyrin. The method was applied to the synthesis of trans-A₂B₂-tetraarylporphyrins and the products were obtained with only a trace amount of one scrambling product. The synthesis of two important building blocks for porphyrin synthesis, mono and di-sulfonamide alkylated 5-substituted dipyrromethanes, was achieved by the addition of 5-substituted dipyrromethane to N-tosyl imine. The application of mono and di-sulfonamide alkylated 5-substituted dipyrromethanes in ‘2+2’ porphyrin formation reactions is presented.     

A common and stereoselective strategy for the synthesis of N,O,O,O-tetra-acetyl d-ribo-(2S,3S,4R)-phytosphingosine and 2-epi-jaspine B

A common and stereoselective strategy for the synthesis of N,O,O,O-tetra-acetyl d-ribo-(2S,3S,4R)-phytosphingosine and 2-epi-jaspine B was achieved by using Grignard addition on N-benzyl sugar lactamine and Wittig olefination as key steps.     

A total synthesis of (R,S)S-glucoraphanin

A total synthesis of (R,S)_S-glucoraphanin (GRP) has been completed by a novel, simple and convenient method in high overall yield (17% over seven steps). The study describes a method for the synthesis of natural and unnatural (methylsulfinyl)alkyl glucosinolates (GLs) and also opens useful pathways to synthesize GRP as well as other sulfinyl GLs.     

A green route for microwave synthesis of sodium tungsten bronzes NaxWO3 (0<x<1)

A green route has been developed for microwave synthesis of sodium tungsten bronzes Na_xWO₃ (0<x<1) from Na₂WO₄, WO₃ and tungsten powder. The hybrid microwave synthesis was carried out in argon atmosphere using CuO powder as the heating medium. Tungsten powder is used as the reducing agent instead of the alkali metal iodides previously used for the microwave synthesis of oxide bronzes. The prepared samples were characterized by powder X-ray diffraction, energy-dispersive X-ray analysis and scanning electron microscopy, and their phase constitutions, crystal structures and morphologies are in consistence with that in the literature. This synthesis method is simple, green and atom economic, and promising for preparation of other oxide bronzes and related compounds.     

Direct syntheses of Lan+1NinO3n+1 phases (n=1, 2, 3 and ∞) from nanosized co-crystallites

A new direct route for the “bottom up” syntheses of phases in the La_n+1Ni_nO_3n+1 series (n=1, 2, 3 and ∞) has been achieved via single-step heat treatments of nanosized co-crystallized precursors. The co-crystallized precursors were prepared using a continuous hydrothermal flow synthesis system that uses a superheated water flow at ca. 400 °C and 24.1 MPa to produce nanoparticulate slurries. Overall, a significant reduction in time and number of steps for the syntheses of La₃Ni₂O₇ and La₄Ni₃O₁₀ was achieved compared with more conventional synthesis methods, which typically require multiple homogenization and reheating steps over several days.     

Mono-benzyl substituted cis,cis-1,3,5-triaminocyclohexanes

Unsymmetrical derivatives of the versatile molecule cis,cis-1,3,5-triaminocyclohexane (tach) have been prepared using a new metal-promoted synthesis to give the mono N-substituted tach ligands. This new method enables the synthesis of these molecules selectively and in good yields and purity.     

Efficient synthesis of chiral C2-symmetric diamines via allylboration of bis-N,N′-metallodiimines

An enantioselective synthesis of C₂-symmetric bis-homoallylic aromatic and heteroaromatic diamines in 54-89% yields, in 73-94% de and ?98% ee has been achieved via the allylboration of the corresponding N,N′-bis(trimethylsilyl)dialdimines and N,N′-bis(diisobutylalumino)dialdimines with B-allyldiisopinocampheylborane in the presence of methanol, followed by alkaline hydrogen peroxide workup. One-pot synthesis of stable N,N′-bis(benzaldimine-triethylborane) complexes and subsequent allylboration to afford benzene diamines is also described.     

Efficient synthesis of N,N′-dialkyl-N″-dialkylaminocarbothioyl thioureas from cyclic secondary amines, CS2, and N,N′-dialkyl carbodiimides in water

A mild, convenient, and practical one-pot procedure for direct synthesis of N,N′-dialkyl-N″-dialkylaminocarbothioyl thioureas is described via three-component reaction of cyclic secondary amines, CS₂, and N,N′-dialkyl carbodiimides in water at room temperature.     

Synthesis, structure, and magnetic properties of SrMn1−xGaxO3−δ (x=0-0.5) perovskites

We report the synthesis of SrMn_1−xGa_xO_3−δ perovskite compounds and describe the dependence of their phase stability and structural and physical properties over extended cation and oxygen composition ranges. Using special synthesis techniques derived from thermogravimetric measurements, we have extended the solubility limit of random substitution of Ga³⁺ for Mn in the cubic perovskite phase to x=0.5. In the cubic perovskite phase the maximum oxygen content is close to 3−x/2, which corresponds to 100% Mn⁴⁺. Maximally oxygenated solid solution compounds are found to order antiferromagnetically for x=0-0.4, with the transition temperature linearly decreasing as Ga content increases. Increasing the Ga content introduces frustration into the magnetic system and a spin-glass state is observed for SrMn_0.5Ga_0.5O_2.67(3) below 12 K. These properties are markedly different from the long-range antiferromagnetic order below 180 K observed for the layer-ordered compound Sr₂MnGaO_5.50 with nominally identical chemical composition.     

Synthesis and derivatisation of N,N′-trisubstituted 1,2-diamines derived from (1R,2R)-1,2-diaminocyclohexane

The synthesis of N,N′-trisubstituted 1,2-diamines can be achieved by simple reduction of an aminal derived from (1R,2R)-diaminocyclohexane. We comment on the scope and limitation of this reduction and discuss its application towards the synthesis of unsymmetrical N,N′-tetrasubstituted 1,2-diamines.     

Synthesis and reactivity of N-aryl substituted N-heterocyclic silylenes

The synthesis of two N-aryl substituted 2-silaimidazolidenes 9a, b by metal-reduction of the appropriate silicon(IV) heterocycles is reported. Structural as well as spectroscopic data obtained for the N-aryl substituted N-heterocyclic silylenes (NHSi) are very close to those obtained previously for their N-alkyl substituted counterparts. NHSis 9a, b are used as starting materials for the synthesis of a series of dichalcogenadisiletanes 19-24 and for of a mono silylene tungsten complex 29. The reactivity studies revealed only marginally differences between the N-aryl substituted NHSis 9a, b and previously described N-alkyl substituted silylenes.     

A chiron approach to (1R,2R,5S,7R)-2-hydroxy-exo-brevicomin, a component of the volatiles produced by the male mountain pine beetle, Dendroctonus ponderosae

A chiron approach to a synthesis of (1R,2R,5S,7R)-2-hydroxy-exo-brevicomin 1, a component of the volatiles obtained from male mountain pine beetles, Dendroctonus ponderosae has been achieved. Our synthesis started with commercially available d-mannitol and involved Wittig olefination, acid catalysed one-pot hydrogenation and internal acetalization as key steps.