Mild and Efficient PtO2-Catalyzed One-Pot Reductive Mono-N-alkylation of Nitroarenes

A mild and efficient one-pot reductive monoalkylation of nitroarenes has been described using aldehydes as alkylating agents, molecular hydrogen as a reducing agent, and PtO₂ as a catalyst in methanol. This methodology is found to be applicable for both aliphatic and aromatic aldehydes and for a wide variety of nitroarenes.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Commuications® to view the free supplemental file.     

Three-component coupling reactions in ionic liquids: One-pot synthesis of isoxazolidines

1-Butyl-3-methylimidazolium based ionic liquids are found to accelerate significantly the intermolecular 1,3-dipolar cycloaddition of nitrones derived in situ from aldehydes and phenyl hydroxylamine, with electron deficient olefins to afford enhanced rates and improved yields of isoxazolidines with high regio- and diastereoselectivity.     

Influence of varying hard segments on the properties of chemically crosslinked moisture‐cured polyurethane‐urea

Polyurethane prepolymers are widely used in the reactive hot melt adhesives and moisture‐cured coatings. The chemically crosslinked moisture‐cured formulation based on PEG‐1000 and isophorone diisocyanate was prepared with NCO/OH ratio of 1.6:1.0. Trimethylol propane was used as a crosslinking agent. The excess isocyanate of the prepolymer was chain extended in the ratio of 2:1 (NCO/OH) with different aliphatic diols, and 4:1 with different aromatic diamines. The polymer network maturation during moisture cure was followed by dynamic mechanical thermal analyzer (DMTA) instrument. The thermal and dynamic mechanical properties of the crosslinked polymers were evaluated using thermogravimetric analysis, differential scanning calorimetric analysis and DMTA. Surface properties were evaluated through angle‐resolved X‐ray photoelectron spectroscopy. The present article discusses the physical properties of moisture‐cured polyurethane‐urea (MCPU) containing chemical crosslinks in the hard segment. The complete moisture‐cured polymers showed amorous results toward room temperature modulus, tensile strength, hardness, thermal stability, and transparency. The surface properties showed the enrichment of soft segments. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 102–118, 2006     

Studies on physico-chemical changes in zeolite beta in mononitration of toluene

In the present work, the stability and regenerability of H-Beta zeolite in toluene mononitration is studied. Nitration of toluene is carried out in batch mode under reflux conditions using various molar ratios of toluene and nitric acid. Semi batch experiments under reflux are also conducted where nitric acid is dosed at predetermined rates to the reaction mixture containing toluene and the catalyst. The catalyst used in semi batch experiments is found to exhibit consistent performance upto three cycles. The possible cause of consistent activity of the catalyst with respect to para-selectivity has been explored. The physico-chemical changes, if any, in the catalyst is examined for structural stability and presence of pore blockages using sophisticated analytical tools like XRD, EDX, FTIR and ²⁷Al MAS-NMR. These studies indicate the commercial potential of cleaner option of replacing sulfuric acid with zeolites in toluene nitration. Published in Russian in Kinetika i Kataliz, 2009, Vol. 50, No. 1, pp. 141–148. The article is published in the original.     

A simple and efficient enantioselective route to 2,6-disubstituted piperidines: synthesis of (2R,6S)-isosolenopsin A and (2S,6R)-isosolenopsin

The enantioselective synthesis of 2,6-cis-disubstituted piperidine alkaloids, (2R,6S)-isosolenopsin A 2 and (2S,6R)-isosolenopsin 5 from fire ant venom is described. Starting from the dodecanal and decanal, the synthesis presents two key steps. The first step involves Keck allylation to afford the chiral homoallylalcohol with the required stereochemistry and the second key step consists of Grubbs olefin cross metathesis. The synthesis was achieved in five steps with 44% overall yield.     

Understanding the differences between single- and multiobjective optimization for the conservation of multiple species

The purpose of this study is to understand how solutions from single- and multiobjective optimization for the conservation of multiple species are different and what impacts these differences. We identify optimal conservation investment allocations maximizing expected species' habitat ranges for multiple pairs of species using two approaches in the central and southern Appalachian region. We find that disparities between the two approaches are affected by differences in the involved species' expected habitat ranges (i.e., contrasting and similar) and their correlation pattern (i.e., positive, negative, and insignificant). Using a single metric by aggregating species' habitats for multiple species to carry out single-objective optimization is shown to favor the species with a larger habitat distribution more if the involved species' expected habitat distributions are negatively correlated and their distribution difference is larger. Framing multiple metrics of species' habitats separately using multiobjective optimization for the same set of multiple species, in contrast, does not show such a drastic disparity.     

An overview of degradation in solid oxide fuel cells-potential clean power sources

Journal of Solid State Electrochemistry - Solid oxide fuel cells (SOFCs) have emerged as the potential power generating devices, being profoundly effective, biofuel-based, and causing negligible...     

Thrust distribution and decays of the ϒ bound states

We have studied the topologies of hadronic events in e⁺e^- annihilation data taken in the region of the upsilon resonances with the non-magnetic CUSB detectors at CESR. Using a thrust-like variable we compare the decay of ?, ?′ and ?Prime; find for ?″ a significant excess of high thrust events, which we interpret as evidence for electric dipole transitions.     

The inclusive reactions π+d → π− + anything and π+d → π−π− + anything at 6 and 24 GeV/c

Inclusive production of π^? mesons has been studied with 6 and 24 GeV/cπ⁺ beams interacting in deuterium bubble chambers. The energy dependence of the inclusive spectra is discussed. In comparisons with π⁺p inclusive interactions, we observe that projectile fragmentation is not independent of the nature of the target at 6 GeV/c. Cross sections and ratios of cross sections are presented. Two-particle correlations are found to be similar at both energies.     

Bifunctional nanocrystalline MgO for chiral epoxy ketones via Claisen-Schmidt condensation-asymmetric epoxidation reactions

Design and development of a truly nanobifunctional heterogeneous catalyst for the Claisen-Schmidt condensation (CSC) of benzaldehydes with acetophenones to yield chalcones quantitatively followed by asymmetric epoxidation (AE) to afford chiral epoxy ketones with moderate to good yields and impressive ee's is described. The nanomagnesium oxide (aerogel prepared) NAP-MgO was found to be superior over the NA-MgO and CM-MgO in terms of activity and enantioselectivity as applicable in these reactions. An elegant strategy for heterogenization of homogeneous catalysts is presented here to evolve single-site chiral catalysts for AE by a successful transfer of molecular chemistry to surface metal-organic chemistry with the retention of activity, selectivity/enantioselectivity. Br?nsted hydroxyls are established as sole contributors for the epoxidation reaction, while they add on to the CSC, which is largely driven by Lewis basic O2-sites. Strong hydrogen-bond interactions between the surface -OH on MgO and -OH groups of diethyl tartrate are found inducing enantioselectivity in the AE reaction. Thus, the nanocrystalline NAP-MgO with its defined shape, size, and accessible OH groups allows the chemisorption of TBHP, DET, and olefin on its surface to accomplish single-site chiral catalysts to provide optimum ee's in AE reactions.