Asymmetric CuH-catalyzed Reductive Coupling of Allenamides with Carbonyl Electrophiles & Development of Nanocatalysts for Heterogeneously Catalyzed Buchwald-Hartwig Amination

Many drugs and natural products contain multiple stereogenic carbons bearing heteroatoms throughout their carbon framework. Therefore, methods that can efficiently install multiple heteroatoms on a molecule are valuable. Reductive coupling reactions have been extensively studied, and the allylation of carbonyls via the reductive coupling approach has been a key method for generating chiral tertiary and secondary allylic alcohols. This work utilizes inexpensive Cu for the asymmetric reductive coupling of allenamides with carbonyls to simultaneously install two heteroatoms (oxygen and nitrogen) on the product. These molecules have a polarity profile that make them difficult to make using traditional methods. Herein, we report a method for the asymmetric reductive coupling reactions. Chapter 1 describes the development of a regiodivergent and diastereoselective CuH-catalyzed reductive coupling of N-based allenes and carbonyls, where stereoselectivity is controlled by a chiral auxiliary and regioselectivity is modulated by catalyst tuning through choice of ligand. This protocol provides access to novel linear and branched products. The linear products underwent standard chemical transformations to furnish (S)- boivinianin-A, a natural product with a γ-lactone motif. Chapter 2 details the development of the first asymmetric enantioselective aminoallylation of ketones, which features the first reported case of a reversible aminoallylation event in reductive coupling processes. This protocol provides an atom-economical approach for the synthesis of 1,2-aminoalcohols. The reaction paradigm was expanded to incorporate aldehydes as electrophiles to asymmetrically produce secondary alcohols. The Buchwald Hartwig Amination is a powerful reaction for the synthesis of aryl amines. They are extensively used in industrial processes. Currently, homogeneous catalysts are more active and selective than heterogeneous catalysts and are therefore favored in industrial processes. Unfortunately, the use of homogeneous organic palladium complexes as catalysts incurs costs in downstream purification processes when removing palladium impurities. Heterogeneous catalysis faces no such issues because it is easily removed via filtration. These heterogeneous catalysts also have the added benefit of reusability, which makes the development of such a system valuable. Chapter 3 describes our efforts to develop a heterogeneously catalyzed Buchwald-Hartwig Amination employing nanoparticles synthesized via the Strong Electrostatic Absorption method as a catalyst. The development of this reaction, scope, and recycling studies are discussed herein

Technical change and some British multinationals in Kenya: some global considerations

IDS Working Paper No. 228 examined the behaviour of the subsidiaries of seven British Multinationals in Kenya with regard to their generation and acquisition of new technology. This Working Paper is complementary to the earlier one insofar as it examines to that extent the behaviour of the Kenyan subsidiaries is explicable in terms of the organisation of the global market in each industry. The global market is thus described, the role of the particular firm situated and an evaluation made of the extent to which this role explains the behaviour of the Kenyan subsidiaries. Some tentative inclusions are offered, but the limitation of sample size is emphasized

Silicon Burning II: Quasi-Equilibrium and Explosive Burning

Having examined the application of quasi-equilibrium to hydrostatic silicon burning in Paper I of this series, Hix & Thielemann (1996), we now turn our attention to explosive silicon burning. Previous authors have shown that for material which is heated to high temperature by a passing shock and then cooled by adiabatic expansion, the results can be divided into three broad categories; \emph{incomplete burning}, \emph{normal freezeout} and \emph{$\alpha$-rich freezeout}, with the outcome depending on the temperature, density and cooling timescale. In all three cases, we find that the important abundances obey quasi-equilibrium for temperatures greater than approximately 3 GK, with relatively little nucleosynthesis occurring following the breakdown of quasi-equilibrium. We will show that quasi-equilibrium provides better abundance estimates than global nuclear statistical equilibrium, even for normal freezeout and particularly for $\alpha$-rich freezeout. We will also examine the accuracy with which the final nuclear abundances can be estimated from quasi-equilibrium.Comment: 27 pages, including 15 inline figures. LaTeX 2e with aaspp4 and graphicx packages. Accepted to Ap

QUALITATIVE AND QUANTITATIVE PHYTOCHEMICALANALYSIS AND DPPH RADICAL SCAVENGING ACTIVITY OF DIFFERENT EXTRACTSOF FLOWER OF BAUHINIA ACUMINATA LINN

Objective: Bauhinia acuminate L (Fabaceae) is a species of flowering shrub native to tropical south eastern Asia. The flowerof B. acuminataare used against various skin diseases,worms, tumours and diabetes. The Indian vaiydas recommended as a remedy to treat severe biliousness.The qualitative and quantitative estimation of phytochemical constituents in various extracts and the antioxidant potential of flower of Bauhinia acuminata were evaluated.Methods: All the analysis was done based on standard protocols.Results: The phytochemical screening reveals the presence of various primary and secondary metabolites like sugar, carbohydrate, amino acid, fat, quinone, steroids, phenol, saponin, alkaloids, and acid content. In quantitative analysis the important secondary metabolites such as alkaloids and phenolic compounds were estimated in all the extracts.The ethanol and chloroformextract produced significant antioxidant properties in a dose-dependent manner. DPPH free radical scavenging assay of ethanol and chloroform extracts of flower exhibited IC 50 values of 24.44±1.201μg/ml and 196.68±0.456μg/ml respectively. At 1000 μg/ml concentration both extracts shows maximum radical scavenging activity (98.97% and 85.67 %).Conclusion: The findings of this study indicate that this plant is medicinal with prominent antioxidant property

Opportunities in Africa for training in genome science

Genome science is a new type of biology that unites genetics, molecular biology, computational biology and bioinformatics. The availability of the human genome sequence, as well as the genome sequences of several other organisms relevant to health, agriculture and the environment in Africa necessitates the development and delivery of several types and levels of training that will enhance the use of genome data and the associated computational resources. A survey of initiatives that provide opportunities for training in genome science is presented. Current efforts to increase the ability of African scientists to computationally process and analyse genomic and post-genomic data have the potential to produce excellent scientists who perform cutting-edge, hypothesis-based research, and who will accelerate the continent's scientific and technological development