A well-defined silica-supported aluminium alkyl through an unprecedented, consecutive two-step protonolysis-alkyl transfer mechanism

Impregnation of [(AliBu(3))(Et(2)O)] on partially dehydroxylated SBA-15 affords a mesoporous material bearing the well-defined single site surface aluminium species [(≡SiO)(2)Al(iBu)(Et(2)O)].     

Distribution of Arithmetic Functions on Particular Subsets of Integers

Lithuanian Mathematical Journal - Let Q1, . . . , Qt ∈?[x] be polynomials with no constant term for which each linear combination m1Q1(x) + · · ·+mtQt (x) with m1, . . ....     

Action de l'Acide Perpropionique sur le Phosphate de Diphenyle et de p -Nitrophenyle. Destruction et Etude du Mecanisme D'Hydrolyse en Phase Aqueuse Micellaire

L'action de l'acide perpropionique CH 3 CH 2 CO 3 H a été étudiée en milieu micellaire (chlorure de cétyl triméthyl ammonium, CTACl) sur le phosphate de p -nitrophényle et de diphényle (PNPDPP). La destruction est rapide et totale, elle a montré l'intérêt de ce système non agressif. L'utilisation simultanée des spectroscopies UV-visible, IR, et RMN du 31 P a permis de mieux comprendre la réaction et de proposer un mécanisme pour la déphosphorylation du PNPDPP par l'acide perpropionique comportant la formation d'un peranhydride intermédiaire de formule (PhO) 2 P(O)OOC(O)CH 2 CH 3 ; l'évolution de ce dernier a été étudiée en phase aqueuse micellaire (pH ～ 9, CTACl) et par voie radicalaire. The reaction of perpropionic acid CH 3 CH 2 CO 3 H with p -nitrophenyl diphenyl phosphate (PNPDPP) has been carried out in micellar medium (cetyltrimethylammonium chloride, CTACl) providing the fast and complete destruction of PNPDPP. UV-visible, IR, and 31 P NMR spectroscopies allow a better understanding of the reaction. A mechanism for PNPDPP dephosphorylation by peroxyacids is proposed. A peranhydride intermediate, (PhO) 2 P(O)OOC(O)CH 2 CH 3 , is formed; its evolution in buffered micellar medium (pH ～ 9, CTACl) and under organic radical conditions has been studied.     

A New Route to 2-Aminoalkanephosphonic Acids

The phosphonic acids and their esters, which are more resistant to hydrolysis than phosphates, could find wide application in biochemistry as regulators for metabolic processes¹.     

Precursor-directed assembly of complex oxide nanobeads: the role of strongly coordinated inorganic anions

The use of an inorganic perrhenate ligand in the structure of early-transition-metal alkoxide precursors permits to achieve uniform self-assembly of the primary nanoparticles produced by their hydrolysis. The latter has been carried out in a hydrocarbon reaction medium by the addition of water with vigorous stirring, either in the pure form or in solutions in parent alcohols. The self-assembly is guided by the surface charge enhanced by the presence of strongly coordinated anions as determined by zeta potential measurements. The aggregation process has been followed in real time by nanoparticle tracking analysis (NanoSight technique). The reaction products are spherical aggregates with a size that can be efficiently controlled through the polarity of the reaction medium. The produced nanobeads have been characterized by TEM, SEM-EDS, DLS, nitrogen adsorption, and FTIR. The coordination of metal centers has been investigated using EXAFS spectroscopy. The aggregates remain amorphous on thermal treatment of up to 700 °C (24 h treatment) but crystallize when treated at 1000 °C. This latter process is associated with the total loss of rhenium content and offers early-transition-metal oxides as products.     

Design and synthesis by click triazole formation of paclitaxel mimics with simplified core and side-chain structures

A library of paclitaxel (taxol) mimics was obtained by a straightforward strategy involving rational design and an efficient synthesis of a simplified taxane core substitute, together with a click-chemistry combinatorial search for phenylisoserine side-chain surrogates.     

Alkylation de quelques composés carbonylés par des groupes tertiaires. Utilisation de la réaction de friedel-crafts dans la synthèse d'ésters

t-Alkylation of carboxylic esters via their ketene alkyl trimethylsilyl acetals by the Friedal-Crafts reaction allows the synthesis of new highly hindered compounds. A new route using sodium amide in dimethoxyethane, for the preparation of trimethylsilylenol ethers of ketones, is described. The α-t-butylation of these compounds permits the synthesis of new crowded pentasubstituted ketones. The limits as well as the performance of the method have been studied.