Crystallographic report: 1,3,5,7‐Tetraisopropyl‐2,4,6,8,9,10‐hexathia‐1,3,5,7‐tetrastanna‐adamantane

The crystal structure of ⁱPr₄Sn₄S₆ consists of isolated molecules that contain an adamantane‐like Sn₄S₆ core. The tin atoms are coordinated nearly tetrahedrally, with Sn–S distances ranging from 2.397(1) to 2.411(1) Å. Copyright © 2004 John Wiley & Sons, Ltd.     

3‐Diphenyl­phosphino‐1,2:5,6‐di‐O‐isopropyl­idene‐4‐O‐methyl‐1d‐chiro‐inositol

The novel title compound, C₂₅H₃₁O₆P, contains rigid fused rings which are shown to be similar to the precursor structures. Weak C—H⋯O inter­molecular inter­actions produce two‐dimensional sheets composed of R₄⁴(28) rings.     

Palladium‐katalysierte Kohlenstoff‐Kohlenstoff‐Kupplungsreaktionen: Synthesemethoden

Palladium‐catalyzed coupling reactions belong to the most versatile processes for the construction of carbon‐carbon bonds. This article features the Heck, Stille, and Suzuki reaction, which are especially effective for the coupling of alkenes and arenes.     

1‐allyloxy‐2‐hydroxy‐propyl‐starch: Synthesis and characterization

New reactive unsaturated starch derivatives, 1‐allyloxy‐2‐hydroxy‐propyl‐starches (AHP‐starches), were synthesized by the reaction of waxy maize starch (WMS) and amylose‐enriched maize starch (AEMS) with allyl glycidyl ether in a heterogeneous alkaline suspension containing NaOH and Na₂SO₄. The degree of substitution (DS) was determined by ¹H NMR spectroscopy, and a DS of 0.20 ± 0.01 was found for both AHP‐WMS and AHP‐AEMS, respectively. The AHP derivatives of WMS and AEMS were further characterized with ¹H and ¹³C NMR. It was shown that the AHP substitution was located on the C‐6 hydroxyl group of the glucose residues in the starch. The substitution pattern of the AHP groups along the polymer chain was randomly clustered, as determined by enzymatic digestion using pullulanase, α‐amylase, and amyloglucosidase, followed by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry analysis of the digestion products. With X‐ray diffraction and scanning electron microscopy, no changes in the granular morphology and crystallinity between the unmodified starches and AHP‐starches were detected. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2734–2744, 2007     

Cyclotrimerization of ‘Oxabenzonorbornadiene’: Synthesis of syn‐ and anti‐5,6,11,12,17,18‐Hexahydro‐5,18:6,11:12,17‐triepoxytrinaphthylene

An efficient synthetic route to the concave‐shaped, potentially ionophoric syn‐ and anti‐isomers of 5,6,11,12,17,18‐hexahydro‐5,18:6,11:12,17‐triepoxytrinaphthylene ( 4 ) was elaborated. Starting from ‘oxabenzonorbornadiene’ ( 5 ), the stannylated precursor 9 was prepared in three steps, followed by cyclotrimerization catalyzed by copper(I) thiophene‐2‐carboxylate (CuTC) , which afforded 4 in a syn/anti ratio of 5 : 4.     

1,2:1,3‐Bis(μ‐p‐toluato‐O:O′)‐1‐(triphenylphosphine‐P)‐1‐ruthena‐closo‐undecaborane

The title compound, [(PPh₃)(p‐MeC₆H₄COO)₂RuB₁₀H₈], contains an 11‐vertex closo‐type RuB₁₀ cluster fused to two symmetric exo­poly­hedral Ru—O—C—O—B five‐membered rings. Principal distances include Ru—B 2.010 (5)–2.392 (4) Å and Ru—O 2.218 (5) and 2.222 (2) Å.     

Acid‐Labile Amphiphilic PEO‐b‐PPO‐b‐PEO Copolymers: Degradable Poloxamer Analogs

Poly ((ethylene oxide)‐b‐(propylene oxide)‐b‐(ethylene oxide)) triblock copolymers commonly known as poloxamers or Pluronics constitute an important class of nonionic, biocompatible surfactants. Here, a method is reported to incorporate two acid‐labile acetal moieties in the backbone of poloxamers to generate acid‐cleavable nonionic surfactants. Poly(propylene oxide) is functionalized by means of an acetate‐protected vinyl ether to introduce acetal units. Three cleavable PEO‐PPO‐PEO triblock copolymers (M_n,total = 6600, 8000, 9150 g·mol⁻¹; M_n,PEO = 2200, 3600, 4750 g·mol⁻¹) have been synthesized using anionic ring‐opening polymerization. The amphiphilic copolymers exhibit narrow molecular weight distributions (Ð = 1.06–1.08). Surface tension measurements reveal surface‐active behavior in aqueous solution comparable to established noncleavable poloxamers. Complete hydrolysis of the labile junctions after acidic treatment is verified by size exclusion chromatography. The block copolymers have been employed as surfactants in a miniemulsion polymerization to generate polystyrene (PS) nanoparticles with mean diameters of ≈200 nm and narrow size distribution, as determined by dynamic light scattering and scanning electron microscopy. Acid‐triggered precipitation facilitates removal of surfactant fragments from the nanoparticles, which simplifies purification and enables nanoparticle precipitation “on demand.”

     

9‐Methyl‐3‐phenyl­diazenyl‐9H‐carbazole: X‐ray and DFT‐calculated structures

The title compound, C₁₉H₁₅N₃, was prepared by condensation of 3‐nitroso­carbazole and aniline with subsequent methyl­ation. The structure is built up of stacks of almost planar mol­ecules. Density functional theory (DFT) calculations predict a completely planar conformation, different from that observed in the crystal lattice. HOMA (harmonic oscillator model of aromaticity) indices, calculated for three aromatic rings, demonstrate the small influence of the azo substituent on π electrons in the carbazole system.