Pd-carbene catalyzed carbonylation reactions of aryl iodides

A series of carbene complexes [PdBr(2)((i)Pr(2)-bimy)L] (C2-C13) with different types of co-ligands (L) have been tested for their catalytic activities in the carbonylative annulation of 2-iodophenol with phenylacetylene in DMF to afford the respective flavone 2a. Complex C12 with an N-phenylimidazole co-ligand showed the best activity and also afforded high yields when the substrate scope was extended to other aryl or pyridyl acetylenes. In addition, catalyst C12 was also efficient in the carbonylative annulation of 2-iodoaniline with acid chlorides giving the desirable 2-substituted 4H-3,1-benzoxazin-4-ones (4) in good yields. Additionally, this Pd-NHC complex also proved to be a very efficient catalyst for the hydroxycarbonylation of iodobenzene derivatives at low catalyst loading and under low CO pressure. These results demonstrate the versatility and efficiency of this phosphine-free Pd(II)-NHC complex in different types of carbonylations of aryl iodides under mild conditions.     

pH-Sensitive pentablock copolymer nanocapsules as nontoxic and efficient gene carriers

A biodegradable amphiphilic pentablock copolymer PAE‐PCL‐PEG‐PCL‐PAE with a pH‐sensitive unit was synthesized for use as a nontoxic, biodegradable carrier for gene delivery by forming nanocapsules entrapping nucleic acid drugs. The PAE block can interact with plasmid DNA to form polyelectrolyte complexes in an acidic environment. At physiological pH, the PAE blocks are deprotonated and form an insoluble skin, resulting in the formation of nanocapsules that encapsulate plasmid DNA. The surface charges of the nanocapsules became almost neutral at pH = 7.4, and their size ranged from 210 to 280 nm. The nanocapsule maintained most of its transfection efficiency even in the presence of serum. These nanocapsules are therefore potential carriers for systemic gene therapy.

     

A rapid and economical method for profiling feature heights during microfabrication

Quality control is an important and integral part to any microfabrication process. While the widths of features often can be easily assessed by light microscopy, the heights of the fabricated structures are more difficult to determine. Here, we present a rapid, accurate, and low-cost method to measure the heights of microfabricated structures during and after the fabrication process. This technique is based on white-light interferometry, which offers accuracy on the submicrometre scale.     

Metal-doped apatitic calcium phosphates: preparation,characterization, and reactivity in the removal of hydrogen sulfide from gas phase

With the expansion of human activities, there are more and more living areas adjacent to industrial and/or agricultural activities such as chemical processes, petroleum processes, paint finishing, food processing, livestock farming, composting plants etc. Bad odor is part of several nuisances caused by industrial and/or agricultural activities. Hydrogen sulfide (H₂S) is a typical odorous molecule which causes foul odor at very low concentration. This molecule is formed in different industrial installations, in particular in coal combustion, and petrochemical refinery. The separation and/or transformation of H₂S from gas phase to odorless products are important processes for sustainable development. In this paper, we communicate the preparation of new sorbents for the sorption of H₂S from a synthetic gas effluent. These sorbents consist in an inorganic phase (hydroxyapatite) as host particles, and well-dispersed particles of a metal oxide as guest particles which are the active phase for the removal of H₂S. At room conditions, iron, lead, and zinc doped calcium phosphates were found to be effective for the removal of H₂S. The performance of the sorbents depends on preparation method and the nature of active phases. This opens new prospects for the treatment of H₂S from gas phase.     

Synthese de C-nucleosides—IX : Purines substituees en position 8 par le desoxy-2 ribose

Benzyl 2-deoxy-3,5-di-O-p-toluyl-d-erythro-pentofuranosyl thioformimidate 3, prepared from nitrile 1, reacts with α-aminocyanoacetic acid derivatives to yield C-imidazole nucleosides which are further cyclized into purines. The 6-mercapto purine 2 is obtained in two different ways.     

The integral variation method for solving systems of differential equations

We sketch the integral variation method for generating approximate solutions to initial value problems involving systems of first-order ordinary differential equations. This new constructive technique is illustrated with applications to the damped oscillator, a nonlinear growth equation, and zonal harmonic perturbations of a near Earth satellite orbit.