Working capital management at Keren Metal, Wood and Cement Works : a manufacturing firm in Eritrea.

Thesis (MBA)-University of Kwazulu-Natal, 2004.Working capital management refers to the financing, investment and control of net current assets within policy guidelines. It seems to have been relatively overlooked, although it is realized that a high proportion of business failures are due to poor decisions concerning the working capital of the firms. This case study is devoted to analyze the working capital practices of Keren Metal, wood and Cement Works, a manufacturing firm operating under joint venture in Eritrea. The study covers areas of working capital management, which encompasses, the working capital investment, working capital finance and working capital policies of the firm. To this end, relevant literature is reviewed and compared to the actual practices of the firm. Based on the gap identified from the comparison of the theory and the application, recommendations has been forwarded as how the working capital should be practiced, so as create value to the partners of the firm

Six-membered ring systems: with O and/or S atoms

A large variety of publications have emerged in 2012 involving O- and S-6- membered ring systems. The increasing number of reviews and other communica- tions dedicated to natural and synthetic derivatives and their biological significance highlights the importance of these heterocycles. Reviews on natural products involve biosynthesis and isolation of enantiomeric derivatives h12AGE4802i, biosynthesis, isolation, synthesis, and biological studies on the pederin family h12NPR980i and xanthones obtained from fungi, lichens, and bacteria h12CR3717i and on the potential chemotherapeutic value of phyto- chemical products and plant extracts as antidiabetic h12NPR580i, antimicrobial, and resistance-modifying agents h12NPR1007i. A more specific review covers a structure–activity relationship of endoperoxides from marine origin and their antitry- panosomal activity h12OBC7197i. New synthetic routes to naturally occurring, biologically active pyran derivatives have been the object of several papers. Different approaches have been discussed for the total synthesis of tetrahydropyran-containing natural products (")-zampanolide h12CEJ16868, 12EJO4130, 12OL3408i, (")-aspergillides A and B h12H(85)587, 12H(85)1255, 12TA252i, (þ)-neopeltolide h12JOC2225, 12JOC9840, 12H(85) 1255i, or their macrolactone core h12OBC3689, 12OL2346i. The total synthesis of bistramide A h12CEJ7452i and (þ)-kalihinol A h12CC901i and the stereoselec- tive synthesis of a fragment of bryostatin h12S3077, 12TL6163i have also been sur- veyed. Other papers relate the total synthesis of naturally occurring carbocyclic and heterocyclic-fused pyran compounds, such as (")-dysiherbaine h12CC6295i, penos- tatin B h12OL244i, Greek tobacco lactonic products, and analogues h12TL4293i and on the structurally intriguing limonoids andhraxylocarpins A–E h12CEJ14342i. The stereocontrolled synthesis of fused tetrahydropyrans was used in the preparation of blepharocalyxin D h12AGE3901i. Polyphenolic heterocyclic compounds have also received great attention in 2012. The biological activities and the chemistry of prenylated caged xanthones h12PCB78i, the occurrence of sesquiterpene coumarins h12PR77i, and the medicinal properties of the xanthone mangiferin h12MRME412i have been reviewed. An overview on the asymmetric syntheses of flavanones and chromanones h12EJO449i, on the synthesis and reactivity of flavones h12T8523i and xanthones h12COC2818i, on the synthesis and biosynthesis of biocoumarins h12T2553i, and on the synthesis and applications of flavylium compounds h12CSR869i has been discussed. The most recent developments in the synthesis and applications of sultones, a very important class of sulfur compounds, were reported h12CR5339i. A review on xanthene-based fluorescent probes for sensing cations, anions, bio- logical species, and enzyme activity has described the spiro-ring-opening approach with a focus on the major mechanisms controlling their luminescence behavior h12CR1910i. The design and synthesis of other derivatives to be used as sensors of gold species h12CC11229i and other specific metal cations h12PC823i have also been described. Recent advances related to coumarin-derived fluorescent chemosen- sors for metal ions h12COC2690i and to monitoring in vitro analysis and cellular imaging of monoamine oxidase activity h12CC6833i have been discussed. The study of various organic chromophores allowed the synthesis of novel dica- tionic phloroglucinol-type bisflavylium pigments h12SL2053i, and the optical and spectroscopic properties of several synthetic 6-aryldibenzo[b,d]pyrylium salts were explored h12TL6433i. Discussion of specific reactions leading to O- and S-membered heterocyclic compounds covers intramolecular radical cyclization h12S2475i and asymmetric enamine and dienamine catalysis h12EJO865i, oxa-Michael h12CSR988i and dom- ino Knoevenagel–hetero-Diels–Alder (hDA) reactions h12T5693i, and the versatility in cycloadditions as well as nucleophilic reactions using o-quinones h12CSR1050i. The use of specific reagents relevant to this chapter includes molecular iodine h12CEJ5460, 12COS561i, samarium diiodide–water for selective reductive transfor- mations h12CC330i, o-quinone methides as versatile intermediates h12CEJ9160i, InCl3 as catalyst h12T8683i, and gold and platinum p-acid mediated insertion of alkynes into carbon–heteroatom s-bonds h12S3401i. The remainder of this chapter discusses the most studied transformations on O- and S-6-membered heterocycles

A comparative study of the Au-catalyzed cyclization of hydroxy-substituted allylic alcohols and ethers

The Au(I)-catalyzed cyclization of hydroxyallylic ethers to form tetrahydropyrans is reported. Employing (acetonitrile)[(o-biphenyl)di-tert-butylphosphine]gold(I) hexafluoroantimonate, the cyclization reactions were complete within minutes to hours, depending on the substrate. The reaction progress was monitored by GC, and comparisons between substrates demonstrate that reactions of allylic alcohols are faster than the corresponding ethers. Additionally, it is reported that Reaxa QuadraPureTM MPA is an efficient scavenging reagent that halts the reaction progress

The Importance of Hydrogen Bonding to Stereoselectivity and Catalyst Turnover in Gold-Catalyzed Cyclization of Monoallylic Diols

Density functional calculations and experiment were used to examine the mechanism, reactivity, and origin of chirality transfer in monophosphine Au-catalyzed monoallylic diol cyclization reactions. The lowest energy pathway for cyclization involves a two-step sequence that begins with intramolecular C–O bond formation by <i>anti</i>-addition of the non-allylic hydroxyl group to the Au-coordinated alkene followed by concerted hydrogen transfer/<i>anti</i>-elimination to liberate water. Concerted S_N2′-type transition states were found to be significantly higher in energy. The two-step cyclization pathway is extremely facile due to hydrogen bonding between diol groups that induces nucleophilic attack on the alkene and then proton transfer between diol groups after C–O bond formation. Importantly, intramolecular proton transfer and elimination provides an extremely efficient avenue for catalyst regeneration from the Au–C σ-bond intermediate, in contrast to other Au-catalyzed cyclization reactions where this intermediate severely restricts catalyst turnover. The origin of chirality transfer and the ensuing alkene stereochemistry is also the result of strong hydrogen-bonding interactions between diol groups. In the C–O bond-forming step, requisite hydrogen bonding biases the tethered nucleophilic moiety to adopt a chair-like conformation with substituents in either axial or equatorial positions, dictating the stereochemical outcome of the reaction. Since this hydrogen bonding is maintained throughout the course of the reaction, establishment of the resultant olefin geometry is also attributed to this templating effect. These computational conclusions are supported by experimental evidence employing bicyclic systems to probe the facial selectivity

Synergistic Configuration of Diols as Br??nsted Bases

As viscous hydroxylic organic compounds, diols are of interest for their functional molecular conformation, which is based on inter- and intramolecular hydrogen (H)-bonds. By utilising steady-state electronic and vibrational spectroscopy, time-resolved fluorescence spectroscopy, and computational analyses, we report the association of the hydroxyl groups of diols via intra- or intermolecular H-bonds to enhance their reactivity as a base. Whereas the formation of an intermolecularly H-bonded dimer is requisite for diols of weak intramolecular H-bond to extract a proton from a model strong photoacid, a well-configured single diol molecule with an optimised intramolecular H-bond is revealed to serve as an effective Br??nsted base with increased basicity. This observation highlights the collective role of H-bonding in acid-base reactions, and provides mechanistic backgrounds to understand the reactivity of polyols in the acid-catalysed dehydration for the synthesis of cyclic ethers at the molecular level