Organocatalytic Trapping of Elusive Carbon Dioxide Based Heterocycles by a Kinetically Controlled Cascade Process

A conceptually novel approach is described for the synthesis of six-membered cyclic carbonates derived from carbon dioxide. The approach utilizes homoallylic precursors that are converted into five-membered cyclic carbonates having a β-positioned alcohol group in one of the ring substituents. The activation of the pendent alcohol group through an N-heterocyclic base allows equilibration towards a thermodynamically disfavored six-membered carbonate analogue that can be trapped by an acylating agent. Various control experiments and computational analysis of this manifold are in line with a process that is primarily dictated by a kinetically controlled acylation step. This cascade process delivers an ample diversity of six-membered cyclic carbonates in excellent yields and chemoselectivities under mild reaction conditions.     

Interest of absorption spectroscopy for the control of industrial processes. Application to H2 massive production

Absorption and TDLA spectroscopies find their applications in a lot of fields of research. The purpose of this article is to show how these methods can bring significant advances in chemical research projects. “H₂ massive production” using nuclear heat together with a thermochemical cycle is an important way to massively produce hydrogen, a potential energy vector. The sulfur–iodine cycle and the hybrid copper-chloride thermochemical cycles are some good candidates for water splitting.     

A synthetic approach to palmerolides via Negishi cross coupling. The challenge of the C15–C16 bond formation

The esterification of fragment C1–C8 (2) with fragment C16–C23 (3) to give iodo derivative 4, followed by a Pd-catalysed coupling with a C9–C15 fragment (7 or 8), may provide a common precursor of most palmerolides. Ligands and reaction conditions were exhaustively examined to perform the C15–C16 bond formation via Negishi reaction. With simple models, pre-activated Pd–Xantphos and Pd–DPEphos complexes were the most efficient catalysts at RT. Zincation of the C9–C15 fragment (8) and cross coupling with 4 required 3 equiv of t-BuLi, 10 mol % of Pd–Xantphos and 60 °C.     

Effect of Bee Pollen on the Mechanical and Thermal Properties of Starch Films

The use of casein, starch and bee pollen as biodegradable materials has been promise. The objective of this work was the development and characterization of films containing casein, pollen and starch. The films were obtained by casting process and the solvent evaporation was performed at 40 °C/24 h. The films characterization was carried out by microscopy, thermal analysis, opacity test, mechanical properties and barrier methods. The starch films presented heterogeneous on microscopy analysis. The thermal behaviors of pollen films were similar. The formulation containing only pollen 3% was unable to form film. The introduction of pollen in starch film formulation improved the mechanical characteristic and thermal stability of films.     

Highly Enantioselective Cross‐Aldol Reactions of Acetaldehyde Mediated by a Dual Catalytic System Operating under Site Isolation

Polystyrene‐supported (PS) diarylprolinol catalysts 1 a (Ar=phenyl) and 1 b (Ar=3,5‐bis(trifluoromethyl)phenyl) have been developed. Operating under site‐isolation conditions, PS‐ 1 a / 1 b worked compatibly with PS‐bound sulfonic acid catalyst 2 to promote deoligomerization of paraldehyde and subsequent cross‐aldol reactions of the resulting acetaldehyde in one pot, affording aldol products in high yields with excellent enantioselectivities. The effect of water on the performance of the catalytic system has been studied and its optimal amount (0.5 equiv) has been determined. The dual catalytic system ( 1 / 2 ) allows repeated recycling and reuse (10 cycles). The potential of this methodology is demonstrated by a two‐step synthesis of a phenoperidine analogue (68 % overall yield; 98 % ee) and by the preparation of highly enantioenriched 1,3‐diols 4 and 3‐methylamino‐1‐arylpropanols 5 , key intermediates in the synthesis of a variety of druglike structures.     

A DFT study of the electronic spectrum of the alpha-keggin anion [Co(II)W(12)O(40)](6-)

Multiplet splittings for several excited configurations of [Co(II)W(12)O(40)](6-) were calculated using DFT methods. In agreement with the experimental interpretation of the spectrum the calculations found that the first strong band corresponds to Co d-d transitions, but it is worth noting that superposed to these transitions there are charge transfer transitions from cobalt to tungsten. The calculations also showed the importance of Jahn-Teller distortions in the excited states. With the exception of the consequences derived from a smaller splitting of d cobalt orbitals the d-d spectrum of [CoCl(4)](2-) is similar to that of the more complex Keggin anion. Finally, the energy of the bielectronic transition (4)A(2) --> (4)T(1)(P) was estimated via an approximate procedure based on ligand field theory.     

Micellar electrokinetic chromatography estimation of size and composition of procyanidins after thiolysis with cysteine

This paper describes the characterization of procyanidin mixtures by acid depolymerization in the presence of cysteine (thiolysis with cysteine) and micellar electrokinetic chromatography (MEKC). Reversed-phase liquid chromatography (RP-HPLC) and MEKC were investigated for the separation of the major components of the depolymerized mixtures (catechins and their cysteinyl derivatives). The solutes could only be effectively separated using MEKC. Two background electrolytes (BGEs) are recommended: (i) 50 mM phosphate at pH 7, containing 40 mM sodium cholate (SC) and 10 mM sodium dodecyl sulfate (SDS); (ii) a BGE with the same composition but containing only 50 mM SDS. The MEKC procedures here reported, are cheap, reliable and fast, and their potential in the determination of the size and composition in procyanidin mixtures has been shown. The proposed MEKC methods were validated by comparison with our intralaboratory reference RP-HPLC method using cysteamine as thiol donor.     

An effectiveness factor you can see

Effectiveness factor values corresponding to carrageenan immobilized yeast beads packed in a continuous tubular fermenter are obtained from the mathematical modelization of the reactor performing ethanol fermentation. Simultaneously, microscopical direct observation of transversal sections corresponding to two different points in the fermenter is in good agreement with the calculated values: An effectiveness factor near to unity gives a uniform cell distribution in beads, as an effectiveness factor near to 0.75 corresponds to a non-uniform cell growth in beads. This observation gives a visual evidence of the validity of the approach used to treat diffusional limitations in biocatalytic particles.