The Huisgen 1,3-dipolar cycloaddition reaction of organic azides and alkynes has gained considerable attention in recent years due to the introduction in 2001 of Cu(1) catalysis by Tornoe and Meldal, leading to a major improvement in both rate and regioselectivity of the reaction, as realized independently by the Meldal and the Sharpless laboratories. The great success of the Cu(1) catalyzed reaction is rooted in the fact that it is a virtually quantitative, very robust, insensitive, general, and orthogonal ligation reaction, suitable for even biomolecular ligation and in vivo tagging or as a polymerization reaction for synthesis of long linear polymers. The triazole formed is essentially chemically inert to reactive conditions, e.g. oxidation, reduction, and hydrolysis, and has an intermediate polarity with a dipolar moment of ∼5 D. The basis for the unique properties and rate enhancement for triazole formation under Cu(1) catalysis should be found in the high ∆G of the reaction in combination with the low character of polarity of the dipole of the noncatalyzed thermal reaction, which leads to a considerable activation barrier. In order to understand the reaction in detail, it therefore seems important to spend a moment to consider the structural and mechanistic aspects of the catalysis. The reaction is quite insensitive to reaction conditions as long as Cu(1) is present and may be performed in an aqueous or organic environment both in solution and on solid support.

Cu-catalyzed azide-alkyne cycloaddition.

Introduced to the Market in the Last Decade (2001−2011) Jiang Wang,† María Sańchez-Rosello,́‡,§ Jose ́ Luis Aceña, Carlos del Pozo,‡ Alexander E. Sorochinsky, Santos Fustero,*,‡,§ Vadim A. Soloshonok,* and Hong Liu*,† †Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Shanghai 201203, China ‡Department of Organic Chemistry, Faculty of Pharmacy, University of Valencia, Av. Vicente Andreś Estelleś, 46100 Burjassot, Valencia, Spain Laboratorio de Molećulas Orgańicas, Centro de Investigacioń Príncipe Felipe, C/ Eduardo Primo Yuf́era 3, 46012 Valencia, Spain Department of Organic Chemistry I, Faculty of Chemistry, University of the Basque Country UPV/EHU, Paseo Manuel Lardizab́al 3, 20018 San Sebastian, Spain IKERBASQUE, Basque Foundation for Science, Alameda Urquijo, 36-5 Plaza Bizkaia, 48011 Bilbao, Spain Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine, Murmanska Street 1, 02660 Kyiv-94, Ukraine

Fluorine in pharmaceutical industry: fluorine-containing drugs introduced to the market in the last decade (2001-2011).

Secondary organic aerosol (SOA) accounts for a significant fraction of ambient tropospheric aerosol and a detailed knowledge of the formation, properties and transformation of SOA is therefore required to evaluate its impact on atmospheric processes, climate and human health. The chemical and physical processes associated with SOA formation are complex and varied, and, despite considerable progress in recent years, a quantitative and predictive understanding of SOA formation does not exist and therefore represents a major research challenge in atmospheric science. This review begins with an update on the current state of knowledge on the global SOA budget and is followed by an overview of the atmospheric degradation mechanisms for SOA precursors, gas-particle partitioning theory and the analytical techniques used to determine the chemical composition of SOA. A survey of recent laboratory, field and modeling studies is also presented. The following topical and emerging issues are highlighted and discussed in detail: molecular characterization of biogenic SOA constituents, condensed phase reactions and oligomerization, the interaction of atmospheric organic components with sulfuric acid, the chemical and photochemical processing of organics in the atmospheric aqueous phase, aerosol formation from real plant emissions, interaction of atmospheric organic components with water, thermodynamics and mixtures in atmospheric models. Finally, the major challenges ahead in laboratory, field and modeling studies of SOA are discussed and recommendations for future research directions are proposed.

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The formation, properties and impact of secondary organic aerosol: current and emerging issues

Due to their abundance, high strength and stiffness, low weight and biodegradability, nano-scale cellulose fiber materials (e.g., microfibrillated cellulose and bacterial cellulose) serve as promising candidates for bio-nanocomposite production. Such new high-value materials are the subject of continuing research and are commercially interesting in terms of new products from the pulp and paper industry and the agricultural sector. Cellulose nanofibers can be extracted from various plant sources and, although the mechanical separation of plant fibers into smaller elementary constituents has typically required high energy input, chemical and/or enzymatic fiber pre-treatments have been developed to overcome this problem. A challenge associated with using nanocellulose in composites is the lack of compatibility with hydrophobic polymers and various chemical modification methods have been explored in order to address this hurdle. This review summarizes progress in nanocellulose preparation with a particular focus on microfibrillated cellulose and also discusses recent developments in bio-nanocomposite fabrication based on nanocellulose.

Microfibrillated cellulose and new nanocomposite materials: a review

Asymmetric enamine catalysis.

An enzymatic approach to combine ring-opening polymerization of e-caprolactone and regioselective acylation of methyl glycopyranosides has been investigated. Candida antarctica lipase B (Novozym 435) catalyzed the regiospecific acylation of methyl galacto- and glucopyranoside and the ring-opening polymerization of e-caprolactone to give methyl 6-O-poly(e-caprolactone)glycopyranosides. The synthetic strategy led to the synthesis of methyl 6-O-poly(e-caprolactone)-β-d-glucopyranoside with a Mw of 3750 and a polydispersity of 1.3. The best results were obtained by drying the system and carrying out the polymerization at 60 °C in bulk, without solvent. The overall conversion from methyl β-d-glucopyranoside was 80%.

Lipase-catalyzed synthesis of methyl 6-O-poly(ε-caprolactone)glycopyranosides

A highly chemo- and enantioselective organocatalytic addition of fluorocarbon nucleophiles, such as 1-fluoro-bis(phenylsulfonyl)methane, toα,β-unsaturated aldehydes is presented (see scheme). The reactions are catalyzed by simple chiral amines and give access to optically active fluorine derivatives in good yields and up to 95 % ee. Notably, the methodology can be applied to the formation of a chiral quaternary carbon center bearing a fluorine atom with high enantioselectivity.

Enantioselective organocatalytic conjugate addition of fluorocarbon nucleophiles to α,β-unsaturated aldehydes

Amino acid-catalyzed direct enantioselective synthesis of β-amino-α-oxyaldehydes

A simple one-pot, three-component, catalytic, highly enantioselective isoxazolidine synthesis

Highly diastereo- and enantioselective catalytic domino thia-Michael/aldol reactions: Synthesis of benzothiopyrans with three contiguous stereocenters

Armando Córdova

Papers

Lipase-catalyzed synthesis of methyl 6-O-poly(ε-caprolactone)glycopyranosides

Enantioselective organocatalytic conjugate addition of fluorocarbon nucleophiles to α,β-unsaturated aldehydes

Amino acid-catalyzed direct enantioselective synthesis of β-amino-α-oxyaldehydes

A simple one-pot, three-component, catalytic, highly enantioselective isoxazolidine synthesis

Highly diastereo- and enantioselective catalytic domino thia-Michael/aldol reactions: synthesis of benzothiopyrans with three contiguous stereocenters