Introduction to the Proceedings of the Fourteenth Symposium on Biotechnology for Fuels and Chemicals

Applied Biochemistry and Biotechnology -     

Intermolecular rhodium catalyzed hydroacylation of allenes: the regioselective synthesis of β,γ-unsaturated ketones

A variety of β-S-substituted aldehydes undergo efficient and regioselective rhodium catalyzed hydroacylation reactions with 1,3-disubstituted and 1,1,3-trisubstituted allenes, to deliver β,γ-unsaturated ketone products. Regioselectivites are controlled primarily by steric factors. The reactions are catalyzed by the complex [Rh(dppe)]ClO₄.     

An efficient synthesis of substituted chrysenes

Substituted chrysenes have been swiftly synthesised by the 6-endo-dig cyclisation of ethynylnaphthalenes using platinum(II) chloride. Cyclisation precursors were directly prepared from commercially available 2-bromoaldehydes in a telescoped synthetic procedure involving a Cannizzaro triggered cascade and subsequent dehydration and desilylation. This short synthetic procedure allows rapid access to derivatives of biologically active molecules with useful electronic properties.     

Use of sugar-based ligands in selective catalysis: Recent developments

This review describes recent development in the use of sugar-derived ligands in the selective synthesis of organic molecules. Developments in the recent literature (2004–2009) are highlighted in the areas of hydrogenation, 1,2- and 1,4-additions of nucleophiles to CO and CNR based substrates, cross-coupling, hydroformylation, oxidation and other reactions. Connections to earlier studies are also noted were relevant. Some suggestions as to the underlying features that make sugar-based ligands highly useful modular ligands in selective catalysis are given. Finally, advice is presented (for the non-specialist) on optimal entry points and basic starting materials for sugar-ligand synthesis.     

Chemoselectivity as a Delineator of Cuprate Structure in Catalytic 1,4‐Addition of Diorganozinc Reagents to Michael Acceptors

Reaction of the cyclic thioacetal (RS)₂CHCHO [R=1/2×? (CH₂)₃? ] with HCCCOMe, followed by treatment with TsCl/DABCO (Ts=tosyl, DABCO=1,4‐diazabicyclo[2.2.2]octane) affords the mono‐protected 1,4‐benzoquinone dithioacetal. The reactivity of this SR‐protected 1,4‐benzoquinone has been compared with the behavior of the analogous OR‐protected acetal in copper‐catalyzed additions of ZnMe₂ by using chiral phosphoramidite ligands. The activation energy for 1,4‐methylation of the latter OR‐acetals with ZnMe₂ (>95 % ee) has been determined for two CuX₂ pre‐catalysts (X=OAc, 12.2 kcal mol^?1; X=OTf, 6.7 kcal mol^?1; Tf=triflate). The dithioacetal SR aromatizes in the presence of Cu^I/ZnMe₂ giving 1,4‐HOC₆H₄S(CH₂)₃SMe through C? S bond formation. The disparate behavior of these two very closely related substrates is in accordance with the formation of closely related cuprate intermediates that were optimized by DFT calculations, supporting the synthetic and kinetic studies and thus defining the mechanisms of both pathways.     

Multifunctional hybrid materials based on transparent poly(methyl methacrylate) reinforced by lanthanoid hydroxo clusters

Three pentanuclear lanthanoid hydroxo clusters of composition [Ln(OH)(5)(abzm)(10)], where Ln = Eu, Tb, Ho and abzm = di(4-allyloxy)benzoylmethanide, have been prepared. The structures have been characterised by means of IR, Raman, elemental analyses and X-ray diffraction, showing a pyramidal square-based cluster core. The clusters (Tb and Ho) exhibit Curie-Weiss Law behaviour, displaying antiferromagnetic ordering at low temperatures. The emission properties of the Eu cluster demonstrate the abzm(-) ligand is an efficient antenna (λ(ex) = 420 nm) only for the sensitisation of Eu luminescence in the visible range, via energy transfer to the (5)D(0) state of the trivalent metal. The clusters have been reacted in the presence of methyl methacrylate and azobisisobutyronitrile to prepare reinforced polymers via radical polymerisation. The obtained materials exhibit swelling upon immersion into organic solvents up to ≈ 110% of their original size, in agreement with the presence of cluster-crosslinked polymeric chains. Also, no loss of transparency was observed in the preparation of the materials. The characteristic red emission of the Eu cluster in also retained in the polymeric material.     

Kinetics study of OH radical reactions with n-octane, n-nonane, and n-decane at 240-340 K using the relative rate/discharge flow/mass spectrometry technique

The kinetics of the reactions of hydroxyl radical with n-octane (k1), n-nonane (k2), and n-decane (k3) at 240-340 K and a total pressure of approximately 1 Torr has been studied using relative rate combined with discharge flow and mass spectrometer (RR/DF/MS) technique. The rate constant for these reactions was found to be positively dependent on temperature, with an Arrhenius expression of k1 = (2.27 +/- 0.21) x 10(-11)exp[(-296 +/- 27)/T], k2 = (4.35 +/- 0.49) x 10(-11)exp[(-411 +/- 32)/T], and k3 = (2.26 +/- 0.28) x 10(-11)exp[(-160 +/- 36)/T] cm3 molecule(-1) s(-1) (uncertainties taken as 2sigma), respectively. Our results are in good agreement with previous studies at and above room temperature using different techniques. Assuming that the reaction of alkane with hydroxyl radical is the predominant form for loss of these alkanes in the troposphere, the atmospheric lifetime for n-octane, n-nonane, and n-decane is estimated to be about 43, 35, and 28 h, respectively.