Aurivillius Phases in the Bi4Ti3O12/BiFeO3 System: Thermal Behaviour and Crystal Structure

Four compounds of the Bi₄Ti₃O₁₂/BiFeO₃ system with the formula Bi₂Bi_n?1(Ti,Fe)_nO_3n+3, n = 3, 4, 4.5 and 6 were studied using high‐temperature X‐ray powder diffraction and differential thermoanalysis methods. The crystal structure of the n = 6 phase was refined by the Rietveld method. An unusual behaviour of thermal expansion attributed to an orthorhombic‐to‐tetragonal transformation was revealed. For all the compounds, the lattice parameter c vs temperature T dependence has three regions in the range of T = 20 –750 °C interpreted as (1) expansion of the initial orthorhombic phase, (2) a pronounced structure reconstruction to the tetragonal phase, (3) an expansion of the tetragonal phase. The crystal structure of Bi₇Ti₃Fe₃O₂₁ based on 6‐layer‐perovskite blocks is proposed from X‐ray powder diffraction data. The Rietveld refinement of the structure in the orthorhombic space group F2mm with lattice parameters a = 5.4699(3), b = 5.4924(3), c = 57.551(3) Å (R_p = 9.4, R_wp = 11.9, R_exp = 4.7, R_B = 4.4 %) shows that a distorted 6‐layer model fits the data of Bi₇Ti₃Fe₃O₂₁.     

Synthesis of 4‐(Isothiazol‐3‐yl)morpholines and 1‐(Isothiazol‐3‐yl)piperazines,and Their Inhibitory Activity towards Acetylcholinesterase

The synthesis of novel triaryl‐substituted 4‐(isothiazol‐3‐yl)morpholines 7 and 8 , and 1‐(isothiazol‐3‐yl)piperazines 9 – 13 by reaction of the corresponding isothiazolium salts 5 and 6 with secondary amines in the presence of t‐BuOK in absolute THF is described. Some representatives of the isothiazoles were evaluated as inhibitors of acetylcholinesterase from Electrophorus electricus.     

The Synthesis of New Organoselenium Heterocyclic Compounds: 2‐aryl‐4‐phenyl‐5,6,7,8‐tetrahydro‐4H‐selenochromenes

We have explored the reactions of 2‐(3‐oxo‐1‐aryl‐3‐phenylpropyl)cyclohexanone ( 1–3 ) with hydrogen selenide in situ in conditions of acid catalysis, and synthesized new 2‐aryl‐4‐phenyl‐5,6,7,8‐tetrahydro‐4H‐selenochromenes ( 4–6 ).     

Synthesis of Substituted 4‐Aroyl‐1‐indanone and 5‐Aroyl‐1‐tetralone

Several substituted 4‐aroyl‐1‐indanones 2 and 5‐aroyl‐1‐tetralones 3 were prepared in good yields from 1‐indanones 1 via a series of reasonable transformations.     

Synthesis, structure and characterisation of the n=4 Aurivillius phase Bi5Ti3CrO15

The n=4 Aurivillius phase, Bi₅Ti₃CrO₁₅, was synthesised by solid state reaction. Rietveld analysis of high resolution neutron diffraction data demonstrated this material to adopt the polar space group A2₁am at room temperature, transforming to the aristotype I4/mmm structure above 650 °C. This phase transition is coincident with an anomaly in DSC signal and relative permittivity, which are characteristic of a ferroelectric-paraelectric phase transition. Bi₅Ti₃CrO₁₅ exhibits paramagnetic behaviour at low temperature, with short range antiferromagnetic interactions, but no evidence for long range magnetic ordering. This is considered a consequence of significant disorder of Ti and Cr over the available octahedral sites, as demonstrated by analysis of neutron diffraction data.     

Preparation and Structures of 2‐Substituted 5‐Benzyl‐3‐methylimidazolidin‐4‐one‐Derived Iminium Salts,Reactive Intermediates in Organocatalytic Transformations Involving α,β‐Unsaturated Aldehydes

Preparations of the title compounds, 5 – 7 (Scheme 1 and Table 1), of their ammonium salts, 9 – 11 (Scheme 2 and Table 2), and of the corresponding cinnamaldehyde‐derived iminium salts 12 – 14 (Scheme 3 and Table 3) are reported. The X‐ray crystal structures of 15 cinnamyliminium PF₆ salts have been determined (Table 4). Selected ¹H‐NMR data (Table 5) of the ammonium and iminium salts are discussed, and structures in solution are compared with those in the solid state.     

Synthesis,Characterization and Crystal Structure of Some Novel 1‐Aryl‐2‐Thioxo‐2,3‐Dihydro‐1H‐Quinazolin‐4‐Ones

The base catalyzed intramolecular nucleophilic cyclization of 1‐(2‐haloaroyl)‐3‐aryl thioureas ( 1a‐i ), in the presence of DMF afforded the 1‐aryl‐2‐thioxo‐2,3‐dihydro‐1H‐quinazolin‐4‐ones ( 2a‐i ). The structures were confirmed by spectroscopic data, elemental analyses and in case of the 2c by single crystal X‐ray diffraction data. The mechanistic studies support an intramolecular nucleophilic substitution (S_NAr mechanism) rather than intramolecular aromatic substitution (S_RN1 mechanism).     

Synthesis of 15‐Cyano‐12‐oxopentadecano‐15‐lactone and 15‐Cyano‐ 12‐oxopentadecano‐15‐lactam

15‐Cyano‐12‐oxopentadecano‐15‐lactone was synthesized in 59% total yield starting from 2‐nitrocyclododecanone by Michael addition to acrylaldehyde, followed by reaction with trimethylsilylcyanide, hydrolysis, ring‐expansion, and Nef reaction. A two‐step, one‐pot synthesis of intermediate 2‐hydroxy‐4‐(1‐nitro‐2‐oxycyclododecyl)butanenitrile from 3‐(1‐nitro‐2‐oxocyclododecyl)propanal was developed and the conditions for the Nef reaction were studied. 15‐Cyano‐12‐oxopentadecano‐15‐lactam was synthesized in 40% total yield starting from 2‐nitrocyclododecanone by Michael addition to acrylaldehyde, followed by Strecker reaction, ring‐expansion, and Nef reaction. The conditions for the Strecker and Nef reactions were studied. The structures of the target compounds, intermediates, and by‐product were characterized by IR, ¹H‐ and ¹³C‐NMR, and elemental analysis or MS.     

The Reconstructive Phase Transformation β‐Co2P → α‐Co2P and the Structure of the High‐Temperature Phosphide β‐Co2P

Metallographical and differential thermoanalytical (DTA) investigatitons indicate that the well known phosphide Co₂P (Pearson code oP12, space group Pnma, Co₂Si type) is not stable up to the melting point, T = 1659 K; it is therefore designated as the low‐temperature phase α‐Co₂P. In the temperature range from 1428 to 1659 K, another, high‐temperature phase, designated as β‐Co₂P, exists. X‐ray powder diffraction investigation of liquid quenched alloys in the composition range x_P = 0.25 to 0.335, with x_P as the mole fraction, show that the high‐temperature phase β‐Co₂P is isotypic with Fe₂P (hP9, P 6 2m). For the ideal composition Co₂P, the unit cell parameters are: a = 5.742(2) Å, c = 3.457(5) Å, c/a = 0.621. Among the binary transition metal‐containing phosphides and arsenides isotypic with Fe₂P, β‐Co₂P is the only known high‐temperature phase and it shows (i) the highest axial ratio c/a and (ii) the “smallest” distortion of the hcp substructure formed by the transition metals atoms in the Fe₂P structure type.     

Synthesis and Reactivity of 2‐(2,2‐Dicyano‐1‐methylvinyl)benzothiazole in Heterocyclic Synthesis: Convenient Route to Some Pyridazinone,Hydrazonoethyl, Thiophene,Phathalic Anhydride and Benzene Derivatives Incorporating a Benzothiazole Moiety

A facile route to some pyridazinone, hydrazonoethyl, thiophene, phathalic anhydride and benzene derivatives incorporating a benzothiazole moiety is reported.     

Chiral NMR discrimination of the diastereoisomeric salts of the H3‐antagonist 2‐[3‐(1H‐imidazol‐4‐ylmethyl)piperidin‐1‐yl]‐1H‐benzimidazole

Diastereomeric salts with optically pure (S)‐α‐methoxy‐α‐(trifluoromethyl)phenylacetic acid (MTPA) were used to discriminate the enantiomers of the chiral H₃‐antagonist 2‐[3‐(1H‐imidazol‐4‐ylmethyl)piperidin‐1‐yl]‐1H‐benzimidazole. Chemical‐shift differences (Δδ) in NMR spectra strongly depend on solvent and stoichiometric ratio. The better observable differentiation occurred for the proton at the 2‐position of the imidazole ring. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and Molecular Structure of New S‐Nucleosides of 5‐(4‐Pyridyl)‐4‐Aryl‐4H‐1,2,4‐Triazole‐3‐Thiols

The synthesis of some new S‐nucleosides of 5‐(4‐pyridyl)‐4‐aryl‐4H‐1,2,4‐triazole‐3‐thiols ( 4a‐n ) is described. Direct glycosylation of ( 4a‐n ) with tetra‐O‐acetyl‐α‐D‐glucopyranosyl bromide in the presence of potassium hydroxide followed by deacetylation using dry ammonia in methanol gave the corresponding 3‐S‐(ñ‐D‐glucopyranosyl)‐5‐(4‐pyridyl)‐4‐aryl‐4H‐1,2,4‐triazoles ( 6a‐n ) in good yields. All the compounds were fully characterized by means of ¹HNMR, ¹³C NMR spectra and elemental analyses. To assist in the interpretation of the spectroscopic data, the crystal structure of 3‐S‐(2′,3′,4′,6′‐tetra‐O‐acetyl‐β‐D‐glucopyranosyl)‐5‐(4‐pyridyl)‐4‐phenyl‐4H‐1,2,4‐triazole ( 5a ) was determined by X‐ray diffraction.     

固相合成甲胺基阿维菌素苯甲酸盐

To implement the solid phase synthesis of 4““-epi-methylamino-4““-deoxyavermecfin B1 benzoate, tert-butyldimethylsilylchloride was chosen for the first solution synthesis. Then a novel silyl chloride resin 1, achieved from hydroxymethyl polystyrene resin and dimethyldichlorosilane, was used successfully for the attachment of avermectin B1 2. Through oxidation, amination formation, cleavage, and benzoate formation, resin bounded avermectin B1 9 gave 4““-epi-methylamino-4““-deoxyavermectin B1 benzoate 3.     

A Convenient Synthesis of Functionalized α‐Methylidenebutano‐4‐lactams

A concise synthetic approach to functionalized α‐methylidenebutanolactams has been developed. The synthetic strategy is based on the preliminary assembly of the lactam template equipped with appropriate functionalities. Subsequent installation of the methylidene by a metalation/alkylation/elimination sequence completed the elaboration of the racemic title compounds.     

Synthesis,Crystal Structure and Characterization of Hexakis[2‐methoxy‐4‐formylphenoxy]cyclotriphosphazene

The new cyclotriphosphazene derivative N₃P₃(OC₆H₃OCH₃COH)₆ ( 1 ) was synthesized from hexachlorocyclotriphosphazene, N₃P₃Cl₆, and 4‐hydroxy‐3‐methoxybenzaldehyde in acetonitrile in the presence of K₂CO₃. The structure of 1 was verified by means of elemental analysis, IR, ¹H NMR, ¹³C NMR, ³¹P NMR spectra, thermal analysis and X‐ray diffraction.     

Synthesis,Molecular Structure and Coordination Chemistry of the First 1‐Aza‐3,7‐diphosphacyclooctanes

The first representatives of a novel type of cyclic bis‐phosphines, namely, 1‐aza‐3,7‐diphosphacyclooctanes ( 4 , 5 ), were synthesized by condensation of 1,3‐bis(arylphosphino)propanes ( 2 , 3 ; aryl = phenyl or mesityl), formaldehyde and 5‐aminoisophthalic acid. Only the meso isomers were obtained, in good to satisfactory yield. The cyclic bis‐phosphines readily form P,P chelate complexes ( 6 , 7 ) with [PtCl₂(cod)] (cod = 1,5‐cyclooctadiene). The bisphosphine 4 and the corresponding complex 6 are soluble in water in the presence of two equivalents of alkali metal hydroxide. The molecular structures of 1‐(meta‐dicarboxyphenyl)‐3,7‐dimesityl‐1‐aza‐3,7‐diphosphacyclooctanes ( 5 ) and cis‐{P,P‐1‐(meta‐dicarboxyphenyl)‐3,7‐diphenyl‐1‐aza‐3,7‐diphosphacyclooctane}dichloroplatinum(II) ( 6 ) are reported.     

Two‐Step Synthesis of 1,3‐Disubstituted 3,4‐Dihydro‐4‐thioxoquinazolin‐2(1H)‐ones from 1‐Bromo‐2‐fluorobenzenes

An efficient synthesis of 3‐alkyl‐3,4‐dihydro‐4‐thioxobenzoquinazolin‐2(1H)‐ones 3 has been accomplished in two steps and in satisfactory yields from 1‐bromo‐2‐fluorobenzenes 1 . Thus, the reaction of 1‐fluoro‐2‐lithiobenzenes, generated by the Br/Li exchange between 1 and BuLi, with alkyl isothiocyanates, gives N‐alkyl‐2‐fluorobenzothioamides 2 , which, in turn, react with a series of isocyanates in the presence of NaH to give the desired products 3 .