Synthesis and structural characterization of a terminal hydroxide containing alumoxane via hydrolysis of aluminum hydrides

A novel terminal hydroxide containing dinuclear alumoxane LAl(OH)OAlL(OCH=N-tBu) (3; L = HC(CMeNAr)2, Ar = 2,6-iPr2C6H3) was prepared by treatment of aluminum dihydride LAlH2 (1) and tert-butyl isocyanate in the presence of trace amounts of water and alternatively from 1 and LAlH(OCH=N-tBu) (2) with water. Compound 2 was obtained from the reaction of 1 and tert-butyl isocyanate.     

Extension of the tandem conjugate addition-Dieckmann condensation: the formal synthesis of tetracenomycin A2

Tandem cuprate addition-Dieckmann condensation is featured in the construction of the polyketide metabolite tetracenomycin A(2). Thus, cyclization substrate 11 was treated with Gilman cuprate Me(2)CuLi to afford anthracene 12. The phenolic acetate protecting group of 12ensured its chemoselective oxidation to reveal terminal quinone 13, which intercepts the previously reported synthesis of tetracenomycin A(2).     

The nonsymmetric pressure tensor in polyatomic fluids

Nonequilibrium molecular dynamics calculations are used to show that polyatomic fluids can support antisymmetric stress. In a homogeneous system where the time dependence of vorticity is a step function, it is shown that the rate at which intrinsic angular velocity approaches its steady-state value ( = 1/2 × u) is determined by the magnitude of the antisymmetric part of the pressure tensor.     

Crystallization of amorphous germanium films

Kinetics of isothermal crystallization has been studied in the temperature range from 375 to 525°C. The kinetic curves are obtained and the rate of isothermal transformation of amorphous films into crystalline ones has been determined. Using experimentally determined kinetic curves the stability diagram of the amorphous films has been plotted in the temperature range from 400 to 525°C. The value of effective activation energy has been defined.     

Micro- and nano-mechanical characterization of polyamide 11 and its composites containing cellulose nanofibers

Nanocomposites from polyamide 11 and dried cellulose nanofibers (CNs), 16–30 nm in thickness and 50–400 nm in length, were prepared via direct melt mixing and their micro- and nano-mechanical properties were studied. (PF) QNM (Quantitative Nanomechanical Mapping) method was used to map nanomechanical properties at the surface of polyamide 11 and nanocomposites. This new AFM method emphasized both the increased modulus in nanocomposites as compared to the matrix and the microstructure on different levels in polyamide 11 and its nanocomposites. PF QNM showed that their crystalline structure consists of bundles of lamellar stacks, 200–350 nm in width and 20–40 nm wide lamellar stacks. Moreover, PF QNM study emphasized higher structural order in nanocomposites with 3 and 5 wt.% CNs and lower in the nanocomposite with 8 wt.% CNs as compared to the reference. These observations were verified and are consistent with both crystallinity values determined by DSC and micro-mechanical test results. The oriented bundles of lamellar stacks, observed by PF QNM, could be considered as the main blocks determining high mechanical properties for the studied nanomaterials.     

Synthesis of 2-amino-5,5-dialkyl-4-arylmethylidene-2-oxazolines from 2-alkyl-4-arylbut-3-yn-2-ols and guanidine

Reaction between 2-alkyl-4-arylbut-3-yn-2-ols and guanidine in refluxing pyridine affords 2-amino-5,5-dialkyl-4-arylmethylidene-2-oxazolines.     

Expedient Strategy for the Synthesis of 5-Acylethynylpyrrole-2-carbaldehydes

5-Acylethynylpyrrole-2-carbaldehydes have been synthesized from the protected pyrrole-2-carbaldehydes by their transition-metal-free topochemical mechanoactivated ethynylation with acylbromoacetylenes in a solid Al₂O₃ medium (room temperature, 6 h, 41–54% yields).     

A Convenient Method for the Synthesis of α-Functionalized Chlorophosphonic Esters

α-Functionalized chlorophosphonic monoesters were easily prepared by a selective chlorination of the corresponding phosphonic diesters with phosphorus oxychloride.