A case of disseminated Candida dubliniensis in a preterm infant : the importance of early detection and management of invasive fungal infections in neonates

This case report highlights the importance of timely diagnosis of disseminated fungal infections in neonates, as well as the increased incidence of infection with non-albicans Candida, and the association with surgical conditions such as necrotising enterocolitis.http://www.sajch.org.za/index.php/SAJCHhb201

Fischer dinuclear and mononuclear bis-carbene complexes of thiophene and thiophene derivatives

The reaction of dilithiated thiophene and thiophene derivatives with group 6 transition metal carbonyl precursors and subsequent alkylation afforded linearly arranged Fischer 2,5-bis-carbene and the rare unsymmetrical 2,3-bis-carbene chelated complexes. The latter requires a second lithiation to occur at an adjacent, less reactive site on the thiophene ring. The control of reactivity sites was investigated and achieved by either blocking more reactive positions with substituents or activating less reactive positions by lithium−halogen exchange reactions. A series of Fischer bis-carbene chelates were synthesized by manipulating the above variables. Structural features of Fischer mono-carbene, mononuclear bis-carbene, and bis-carbene chelated complexes were studied by IR, NMR, and single-crystal X-ray diffractionThe National Research Foundation of South Africa under Grant No. 73679 (S.L.)http://pubs.acs.org/journal/orgnd7hb2017ChemistryChurch History and Church PolicyCivil EngineeringClinical Epidemiolog

Preparation of higher alpha olefin oligomers

M.Sc.The economic growth of a country can be stimulated by value-adding to basic resources e.g., chemical intermediates. Alpha olefins are products of the Sasol Fischer-Tropsch process and oligomerization is one of the most significant beneficiation processes available for these alpha olefins. Alpha olefin oligomers obtained from the cationic oligomerization with BF3/ROH, have been used mainly as base stocks in synthetic lubricants. These oligomers consist of a mixture of isomeric products that complicates the investigation and rational modification of this and other closely related oligomerization processes. A comparison of these isomeric mixtures to alkane standards could assist in the study of these processes, but almost no standards are available. This project was aimed, in part, at establishing a methodology for the synthesis of 1-pentene model oligomers. A model branched 1-pentene dimer and trimer as well as a precursor to the analogous tetramer were prepared. The syntheses of other model oligomers in conjunction with the comparison of the properties of model oligomers with different branching patterns will certainly be of value. Some of the main classes of catalysts were evaluated for the oligomerization of higher alpha olefins and especially of 1-pentene. The BF3/n-BuOH cationic oligomerization of 1-pentene yielded dimers, trimer, tetramers and pentamers consisting of a large number of isomers and the product distribution peaked at the trimer. This is in agreement with previous results for other monomers. Radical oligomerization of 1-pentene with organic peroxide initiators proceeded in low yield. Dimers and trimers consisting of a mixture of isomers were mainly formed. Metallocene catalysts offer a convenient route to single component, structurally well characterized alpha olefin oligomers. A variety of functional group transformations and consequent applications are possible for these oligomers. The general nature of the oligomerization of 1-pentene, 1-hexene and 1-octene with allocene/methylaluminoxane catalysts was investigated. The influence of different metals, the number of cyclopentadienyl groups and substitution on the cyclopentadienyl groups in the metallocene moiety, the reaction temperature and the purity of the monomer were studied. By employing the appropriate metallocene in combination with methylaluminoxane, higher alpha olefin dimers and trimers could be formed in high yield at ambient temperatures. Cp2ZrC12 was the most active of the metallocene catalysts and single isomers were formed with high selectivity. The etallocene-based oligomerization of higher alpha olefins offers great scope for further research and promises a new era in olefin oligomerization

Synthesis and reactivity of metal carbene complexes with heterobiaryl spacer substituents

Mono- and binuclear Fischer carbene complexes, [M(CO)5{C(OR)Ar-ArX}], X = H, {C(OR)M(CO)5}; M, M = W or Cr; R = Me, Et or (CH2)4OMe; Ar = thiophene, N-methylpyrrole or furan units 1–20, were synthesized. For this purpose, mono-, bi- or stepwise lithiated bithiophene, N,N-dimethylbipyrrole, thienylfuran and N-methyl(thienyl)pyrrole were reacted with chromium and tungsten hexacarbonyl precursors. Dilithiation in the 2- and 9-positions of N-methyl(thienyl)pyrrole could not be achieved. Alkylation of acyl metallates with triethyloxonium tetrafluoroborate or methyl trifluoromethanesulfonate in THF afforded not only the expected carbene complexes with ethoxy or methoxy substituents, but in the case of bithiophene with methyl trifluoromethanesulfonate, carbene complexes with alkoxy substituents incorporating a ring-opened tetrahydrofuran moiety. X-Ray crystallographic structure determinations were performed on [W(CO)5{C(OMe)(thienylfuran)}] ( 14), [W(CO)5{C(OMe)(N-methylthienylpyrrole)}] ( 20) and [{W(CO)5}2{µ-C(OEt)(N,N-dimethylbipyrrolylC(OEt)}] ( 12) to assess the role of the heterobiaryl substituent on the structural features of the carbene ligand in the complexes. Complexes [{Cr(CO)5}2{µ-C(OMe)bithienylC(OEt)}] ( 3), [(CO)5Cr{µ-C(OMe)bithienylC(OMe)}W(CO)5] ( 5) and [{Cr(CO)5}2{µ-C(OMe)thienylfuranC(OMe)}] ( 15) were reacted with 3-hexyne to study their behaviour in benzannulation reactions. The major products generated by the biscarbene complexes were regio-selectively determined by the nature of the metal site and that of the heteroatom in the arene rings. The monocarbene complexes [Cr(CO)5{C(OMe)thienylfuran] ( 13) and [Cr(CO)5{C(OEt)(N-methylthienylpyrrole)}] ( 19) were refluxed in THF for 2 hours in the presence of [Pd(PPh4)4] to afforded the carbene–carbene coupled olefinic products and small amounts of the corresponding 2-ethyl(biheteroaryl)acetate. By contrast, the biscarbene complex of thienylfuran ( 15), afforded only the 2,9-diester of thienylfuran

Fischer Dinuclear and Mononuclear Bis-Carbene Complexes of Thiophene and Thiophene Derivatives

The reaction of dilithiated thiophene and thiophene derivatives with group 6 transition metal carbonyl precursors and subsequent alkylation afforded linearly arranged Fischer 2,5-bis-carbene and the rare unsymmetrical 2,3-bis-carbene chelated complexes. The latter requires a second lithiation to occur at an adjacent, less reactive site on the thiophene ring. The control of reactivity sites was investigated and achieved by either blocking more reactive positions with substituents or activating less reactive positions by lithium–halogen exchange reactions. A series of Fischer bis-carbene chelates were synthesized by manipulating the above variables. Structural features of Fischer mono-carbene, mononuclear bis-carbene, and bis-carbene chelated complexes were studied by IR, NMR, and single-crystal X-ray diffraction

Fischer Dinuclear and Mononuclear Bis-Carbene Complexes of Thiophene and Thiophene Derivatives

The reaction of dilithiated thiophene and thiophene derivatives with group 6 transition metal carbonyl precursors and subsequent alkylation afforded linearly arranged Fischer 2,5-bis-carbene and the rare unsymmetrical 2,3-bis-carbene chelated complexes. The latter requires a second lithiation to occur at an adjacent, less reactive site on the thiophene ring. The control of reactivity sites was investigated and achieved by either blocking more reactive positions with substituents or activating less reactive positions by lithium−halogen exchange reactions. A series of Fischer bis-carbene chelates were synthesized by manipulating the above variables. Structural features of Fischer mono-carbene, mononuclear bis-carbene, and bis-carbene chelated complexes were studied by IR, NMR, and single-crystal X-ray diffractionThe National Research Foundation of South Africa under Grant No. 73679 (S.L.)http://pubs.acs.org/journal/orgnd7hb2017ChemistryChurch History and Church PolicyCivil EngineeringClinical Epidemiolog