Synthesis of 1,3,4‐Oxadiazoles and 1,3‐Thiazolidinones Containing 1,4,5,6‐Tetrahydro‐6‐pyridazinone

The reaction of 1,4,5,6‐tetrahydro‐6‐pyridazinone‐3‐carboxylic acid hydrazides ( 1 ) with aromatic aldehydes afforded 1,4,5,6‐tetrahydro‐6‐pyridazinone‐3‐carbonyl aromatic aldehyde hydrazones ( 2a‐2g ). Heterocyclic derivatives linked 1,3,4‐oxadiazole obtained by cyclocondensation of 2a‐2g with acetic anhydride in absolute ethanol, and 2a‐2g cyclized with mercaptoacetic acid in DMF in the presence of anhydrous ZnCl₂ afforded the 1,3‐thiazolidinone derivatives. The structures of the new compounds were established by elemental analyses, IR, ¹H NMR and MS spectral data.     

A three‐dimensional lead(II) coordination polymer: poly[aqua‐μ‐imidazole‐4,5‐dicarboxyl­ato‐lead(II)]

In the title coordination polymer, [Pb(C₅H₂N₂O₄)(H₂O)]_n, the Pb^II atom is seven‐coordinated by one N atom and five O atoms from four individual imidazole‐4,5‐dicarboxyl­ate (HIDC²⁻) groups and one water mol­ecule. It is inter­esting to note that the HIDC²⁻ group serves as a bridging ligand to link the Pb^II atoms into a three‐dimensional microporous open‐framework.     

Poly(2-hydroxyethyl acrylate) hydrogel confined in a hydrophobous porous matrix

A series of interpenetrated polymer networks (IPNs) in which the first component is a porous poly(ethyl methacrylate) (PEMA) hydrophobic network and the second one is a poly(2-hydroxyethyl acrylate) (PHEA) hydrophilic network were synthesized. Equilibrium sorption isotherms can be reduced to a single master curve for all the IPNs when the water absorbed is expressed per gram of PHEA in them. The equilibrium water sorption in immersion is always much smaller than that of pure PHEA. This feature is due to the confining effect of the stiff PEMA matrix. The plasticizing effect of the absorbed water on the PHEA phase was characterized using thermally stimulated depolarization currents, dynamic-mechanical analysis and dielectric relaxation spectroscopy. The results show that the shift of the main relaxation peak towards lower temperatures is unaffected by the presence of the PEMA matrix, and only depends on the water content per gram of PHEA in the IPN.     

Interaction and adhesion properties of polyelectrolyte multilayers

The growth, morphology, and interaction/adhesion properties of supported poly(sodium 4-styrenesulfonate)/poly(allylamine hydrochloride) (PSS/PAH) and DNA/PAH multilayers were investigated by means of surface plasmon resonance spectroscopy, atomic force microscope (AFM) imaging, and AFM-related force measurements. Multilayers were assembled on a prelayer of poly(ethylenimine) (PEI) both with and without drying. SPR results showed a linear growth of the assembly in the case of PSS/PAH multilayers and nonlinear growth for DNA/PAH multilayers. Measurements of forces acting between a bare glass sphere and a multilayer-coated surface indicated repulsive or attractive forces, depending on surface charge, which suggests that, on approach, electrostatic forces dominate. On separation, we observed large pull-off forces in the case of positively charged multilayers and weak pull-off forces in the case negatively charged multilayers. Multiple adhesions and plateau regions observed on separation were interpreted in terms of a bridging of multiple polymer chains between the glass particle and the multilayer and a stretching of the polyelectrolyte loops. The dependence of the pull-off force on the number of deposited layers shows regular oscillations.     

Facile Synthesis and Palladium‐Catalyzed Cross‐Coupling Reactions of 2,3‐Bis(pinacolatoboryl)‐1,3‐butadiene

Treatment of 1,1‐bis(pinacolatoboryl)ethene with an excess of 1‐bromo‐1‐lithioethene gave 2,3‐bis(pinacolatoboryl)‐1,3‐butadiene in high yield. Palladium‐catalyzed cross‐coupling of the resulting diborylbutadiene with aryl iodides took place smoothly in the presence of a catalytic amount of Pd(OAc)₂/PPh₃ and aqueous KOH to give 2,3‐diaryl‐1,3‐butadienes in good yields. The coupling reaction with commercially available 4‐acetoxyphenylmethyl chloride under the same conditions followed by hydrolysis of the acetyl groups gave anolignan B in a one‐pot manner. A variety of [3]‐ to [6]dendralenes were synthesized by palladium‐catalyzed coupling of the diene or 1,1‐bis(pinacolato)borylethene with alkenyl or dienyl halides, respectively, in good yields.     

14‐Membered Cyclopeptides from Paliurus ramosissimus and P. hemsleyanus

Six 14‐membered cyclopeptide alkaloids, i.e., ramosines A–C, mucronine J, and lotusines A and D, were isolated from the roots of Paliurus ramosissimus, and an additional four, hemsines A–D, from the roots of P. hemsleyanus. Among these, ramosines A–C ( 1, 5 , and 6 , resp.) and hemsines A and B ( 7 and 8 , resp.) are new bases of the amphibine‐B type, and hemsines C and D ( 9 and 10 , resp.) are new integerrine‐type alkaloids. Additionally, ramosine C ( 6 ) represents the first 14‐membered cyclopeptide alkaloid possessing a substitution (? OH) at C(13′). Their structural elucidations were based on spectral analysis and molecular‐modeling studies. Pronounced solvent effects in the ¹H‐ and ¹³C‐NMR spectra of these two types of alkaloids were observed.     

Solvothermal Synthesis and Characterization of the New Iron Thioantimonates(III) [Fe(C6H18N4)]FeSbS4 and [Fe(C4H13N3)2]Fe2Sb4S10 Containing FeII and FeIII and Protein‐Analogous [2FeIII‐2S]2+ Clusters

The two new compounds [Fe(tren)]FeSbS₄ ( 1 ) (tren = tris(2‐aminoethyl)amine) and [Fe(dien)₂]Fe₂Sb₄S₁₀ ( 2 ) (dien = diethylendiamine) were prepared under solvothermal conditions and represent the first thioantimonates(III) with iron cations integrated into the anionic network. In both compounds Fe³⁺ is part of a [2Fe^III‐2S] cluster which is often found in ferredoxines. In addition, Fe²⁺ ions are present which are surrounded by the organic ligands. In ( 1 ) the Fe²⁺ ion is also part of the thioantimonate(III) network whereas in ( 2 ) the Fe²⁺ ion is isolated. In both compounds the primary SbS₃ units are interconnected into one‐dimensional chains. The mixed‐valent character of [Fe(tren)]FeSbS₄ was unambiguously determined with Mössbauer spectroscopy. Both compounds exhibit paramagnetic behaviour and for ( 1 ) a deviation from linearity is observed due to a strong zero‐field splitting. Both compounds decompose in one single step.     

Synthesis of Derivatives of Pyrido[4,3‐d]pyrimidin‐4(3H)‐one via an Iminophosphorane

A series of new, 2‐substituted 3‐aryl‐8,9,10,11‐tetrahydro‐5‐methyl[1]benzothieno[3′,2′ : 5,6]pyrido[4,3‐d]pyrimidin‐4(3H)‐ones, compounds 5a – q , were designed and synthesized via the aza‐Wittig reaction as the key step. The iminophosphorane 1 reacted with phenyl isocyanate (or 4‐chlorophenyl isocyanate) to the carbodiimide 4 , which was cyclized to 5 upon addition of different amines, EtOH, or phenols in the presence of a catalytic amount of EtONa or K₂CO₃ (Schemes 1 and 2). The structures of compounds 5 were confirmed by IR, ¹H‐ and ¹³C‐NMR, EI‐MS, elemental analyses, and, in the case of 5l , by single‐crystal X‐ray diffraction (Figure).     

A new rubidium beryllium borate,RbBe4(BO3)3

Single crystals of a new rubdidium beryllium borate, RbBe₄(BO₃)₃, have been obtained by spontaneous nucleation from a high‐temperature melt. This new ortho­rhom­bic (Pnma) structure type contains [Be₂BO₄]⁻ rings, made of two BeO₄ tetra­hedra and one BO₃ triangle, which constitute the basic structural units. The m plane runs through the B and one of the O atoms and intersects the ring. These rings form chains in the a direction, which are connected in the b and c directions to form zeolite‐type cages in which the Rb⁺ cations are located, at sites of m symmetry.