10 years after rio-concepts on the contribution of chemistry to a sustainable development

The direct amino acid-catalyzed asymmetric incorporation of molecular oxygen to organic compounds

We have disclosed the direct catalytic incorporation of 1O2 to aldehydes. The unprecedented amino acid-catalyzed asymmetric alpha-oxidation of aldehydes with molecular oxygen or air proceeded with high chemoselectivity and was a direct entry for the synthesis of both enantiomers of terminal diols. The results demonstrated that simple amino acids accomplished catalytic asymmetric oxidations with molecular oxygen or air, which has previously been considered to be in the domain of enzymes and chiral transition-metal complexes. The efficiency of the catalytic process may warrant the existence of an ancient pathway for the synthesis of hydroxylated organic compounds.

Environmentally Benign Processes for Making Useful Fluorocarbons: Nickel- or Copper(I) Iodide-Catalyzed Reaction of Highly Fluorinated Epoxides with Halogens in the Absence of Solvent and Thermal Addition of CF2I2 to Olefins

Highly fluorinated epoxides react with halogens in the presence of nickel powder or CuI at elevated temperatures to provide a useful and general synthesis of dihalodifluoromethanes (CF(2)X(2)) and fluoroacyl fluorides (R(F)COF) in the absence of solvent. At 185 degrees C, hexafluoropropylene oxide and halogens produce CF(2)X(2) (X = I, Br) in 68-90% isolated yields, along with small amounts of X(CF(2))(n)()X, (n = 2, 3). With interhalogens I-X (X = Cl, Br), a mixture of CF(2)I(2), CF(2)XI, and CF(2)X(2) was obtained. The fluorinated epoxides substituted with perfluorophenyl, fluorosulfonyl, and chlorofluoroalkyl groups also react cleanly with iodine to give CF(2)I(2) and the corresponding fluorinated acyl fluorides in good yields. The reaction probably involves an oxidative addition of fluorinated epoxides into metal surfaces to form an oxametallacycle, followed by rapid decomposition to difluorocarbene-metal surfaces, which alters the reactivity of the difluorocarbene carbon from electrophilic to nucleophilic. The increase of nucleophilicity of difluorocarbene facilitates the reaction with electrophilic halogens. CF(2)I(2) reacted with olefins thermally to give 1,3-diiodofluoropropane derivatives. Both fluorinated and nonfluorinated alkenes gave good yields of the adducts. Reaction with ethylene, propylene, perfluoroalkylethylene, vinylidene fluoride, and trifluoroethylene provided the corresponding adducts in 58-86% yields. With tetrafluoroethylene, a 1:1 adduct was predominantly formed along with small amounts of higher homologues. In contrast to perfluoroalkyl iodides, CF(2)I(2) also readily adds to perfluorovinyl ethers to give 1,3-diiodoperfluoro ethers.

Cocrystallization model for synthetic biodegradable poly(butylene adipate-co-butylene terephthalate)

Synthetic biodegradable poly(butylene adipate-co-butylene terephthalate), P(BA-co-BT), with 56 mol % butylene adipate, BA, was characterized by solid-state NMR spectroscopy, thermal analysis, X-ray diffraction, computer modeling, and polarization microscopy. The NMR study showed the presence of BA and butylene terephthalate, BT. T(1C) NMR measurements proved that some BA and BT units were in crystalline regions. Thermal analysis showed one glass-transition temperature and a single diffuse melting endotherm corresponding to a large melting-point depression of about 100 degrees C compared with poly(butylene terephthalate), PBT. These results suggest that there is only one crystalline phase. An X-ray fiber diagram of a stretched film could be indexed with the same unit cell as that for PBT. Computer modeling showed that the adipate unit fits into the crystal structure of PBT by adopting a TTGTG dihedral angle sequence in the crystalline conformation proposed for the cocrystallization model. The predicted fiber diagram from the proposed model qualitatively agrees with the experimental one. Polarization microscopy revealed that the spherulite growth rate of P(BA-co-BT) was similar to that for poly(butylene adipate), PBA.

Sustainable chemistry: starting points and prospects

We review here the concept of sustainable chemistry (SC), which is still in its early development. One important element of SC is commonly defined as chemical research aiming at the optimization of chemical processes and products with respect to energy and material consumption, inherent safety, toxicity, environmental degradability, and so on. An increasing number of assessment systems containing quantitative indicators for these aspects are currently being developed. In addition, however, SC should also address the societal aspect of sustainability. With respect to scientific research, the societal aspect is defined here by two requirements: (1) the assumptions, objectives and implications of chemical research and its technical application should be made more transparent to various societal actors; (2) uncertainty and ignorance should be treated more explicitly in the course of scientific research. Meeting these requirements is necessary in order to lift the division between the allegedly disinterested and non-normative scientific research and the value-laden sphere of societal needs, preferences and decision-making situations. This, in turn, is understood here as a contribution to a more sustainable scientific practice. We illustrate the two elements of SC-optimization of products and processes as well as including the societal aspect-with the examples of environmental chemistry, green chemistry and the environmental assessment of chemical products. While considerable progress has been made in these fields, the societal aspect of SC remains to be recognized more fully in all branches of chemical research. One prerequisite for this is the inclusion of SC into chemical education from the very beginning.

Biosynthesis of novel thermoplastic polythioesters by engineered Escherichia coli

The development of non-petrochemical sources for the plastics industry continues to progress as large multinationals focus on renewable resources to replace fossil carbon. Many bacteria are known to accumulate polyoxoesters as water-insoluble granules in the cytoplasm. The thermoplastic and/or elastomeric behaviour of these biodegradable polymers holds promise for the development of various technological applications. Here, we report the synthesis and characterization of microbial polythioesters (PTEs), a novel class of biopolymers of general technological relevance. Biosynthesis of PTE homopolymers was achieved using a recombinant strain of Escherichia coli that expressed a non-natural pathway consisting of a butyrate kinase, a phosphotransbutyrylase, and a PHA synthase. Different homopolymers were produced, consisting of either 3-mercaptopropionate, 3-mercaptobutyrate, or 3-mercaptovalerate repeating units, if the respective mercaptoalkanoic acids were provided as precursor substrates to the fermentative process. The PTEs contributed up to 30% (w/w) of the cellular dry weight and were identified as hydrophobic inclusions in the cytoplasm. The chemical and stereochemical homogeneity of the purified PTEs were identified by different methods, and the estimated physical properties were compared to the oxypolyester equivalents, revealing low crystalline order and, for the poly(3-mercaptopropionate) improved thermal stability. The ability to produce PTEs through a biosynthetic route opens up new avenues in the field of biomaterials.

New supported beta-amino alcohols as efficient catalysts for the enantioselective addition of diethylzinc to benzaldehyde under flow conditions

[formula: see text] Polymeric monoliths 10 containing an amino alcohol moiety derived from an industrial waste material represent one of the best ligands for the enantioselective catalytic addition of ZnEt2 to benzaldehyde (99% ee), being recoverable and usable under flow conditions.

Green chemistry: science and politics of change

The chemical industry plays a key role in sustaining the world economy and underpinning future technologies, yet is under unprecedented pressure from the effects of globalization and change in many of its traditional markets. Against this background, what will be needed for the industry to embrace efforts to make it "greener"? We explore some of the issues raised by the development of "green chemistry" techniques and identify potential barriers to their implementation by industry.