University of Windsor

About: University of Windsor is a education organization based out in Windsor, Ontario, Canada. It is known for research contribution in the topics: Population & Argumentation theory. The organization has 10654 authors who have published 22307 publications receiving 435906 citations. The organization is also known as: UWindsor & Assumption University of Windsor.

Metal‐Free Catalytic Hydrogenation

Abstract: Hydrogenation is the addition of hydrogen to unsaturated organic compounds. Such reactions are used for the production of a myriad of chemical products worldwide, from largescale operations including the upgrading of crude oil and the production of bulk commodity materials to the synthesis of a variety of fine chemicals used in the food, agricultural, and pharmaceutical industries. The process of hydrogen addition to unsaturated precursors is mediated by either homogeneous or heterogeneous transition-metal-based catalysts. Blaser et al. place the importance of this chemistry in context, stating that “hydrogen is the cleanest reducing agent and hydrogenation is arguably the most important catalytic method in synthetic organic chemistry both on the laboratory and the production scale”. Historically, hydrogenation began with Sabatier%s 1897 discovery that traces of nickel could mediate the catalytic hydrogenation of olefins and culminated in a share of the 1912 Nobel Prize with Grignard. In the 1960s, the advent of organometallic chemistry gave rise to homogeneous transition-metal-based hydrogenation catalysts for a variety of substrates. The operation of these catalysts hinges on the key step of oxidative addition of hydrogen. More recently, transition-metal systems that effect heterolytic cleavage of hydrogen at a metal center have been uncovered. In these cases, a metal hydride is formed with concurrent protonation of an amido ligand. Non-transition-metal catalysts for hydrogenation reactions are all but unknown. KOtBu has been shown to act as a catalyst effecting the addition of H2 to benzophenone under forcing conditions of 200 8C and greater than 100 bar H2. [6] Organocatalysts have been developed for hydrogenations of enones and imines; however, such systems do not employ H2 directly but rather a surrogate such as a Hantzsch ester as the stoichiometric source of hydrogen. The development of nonmetal hydrogenation catalysts hinges on the discovery of systems that react cleanly with H2, but few are known. Power and co-workers reported the hydrogenation of Ge2–alkyne analogues to give a mixture of Ge2 and primary germane products. Recently we have introduced the concept of “frustrated Lewis pairs”, bulky Lewis acids and bases which are sterically precluded from forming simple Lewis adducts. Mixtures of “frustrated” phosphines and boranes can heterolytically cleave H2, forming phosphonium borates of the form [R3PH][BHR’3]. [14] In very recent work, Bertrand and co-workers have demonstrated that selected carbenes exhibit transition-metal-like reactivity and cleave hydrogen or ammonia to effect a formal oxidative addition of the carbene C atom. Last year, we reported the only nonmetal system known to reversibly activate and liberate H2. The phosphonium borate (2,4,6-Me3C6H2)2PH(C6F4)BH(C6F5)2 (1) is formed by reaction of the phosphine–borane species (2,4,6-Me3C6H2)2P(C6F4)B(C6F5)2 (3) with H2 while heating of the zwitterion 1 above 100 8C liberates hydrogen and regenerates the phosphine–borane 3. Herein, we demonstrate that this system and a related system provide the first metalfree hydrogenation catalysts that effect the addition of molecular H2 to imines, nitriles, and aziridines to produce primary and secondary amines in high yields under relatively mild reaction conditions. The reduction of imines and nitriles is one of the best synthetic methods to generate secondary and primary amines, and has found tremendous importance in the pharmaceutical and fine chemicals industry. The airand moisture-stable phosphonium borates (R2PH)(C6F4)BH(C6F5)2 (R= 2,4,6Me3C6H2 (1) [16] and tBu (2)) are active catalysts for the hydrogenation of C N multiple bonds with H2. For example, imines are reduced in toluene to the corresponding amines cleanly and in high yield at slightly elevated temperatures (80–140 8C) and H2 pressures (1–5 atm) in sealed glass bombs (Table 1, entries 1–6). The amine products are readily separated from residual catalyst by filtration through a plug of silica gel; no other side products are observed in the NMR spectra of the crude reaction mixtures. In the case of a sterically less demanding imine (Table 1, entry 6) no catalytic turnover was noted. Similarly, nitriles are not catalytically reduced, as these donors intervene in the catalytic cycle by binding strongly to the B center of the catalyst. Sequestering the N lone pair by coordination of Ph(H)C=NCH2Ph to B(C6F5)3 (Table 1, entry 7) allowed catalytic imine reduction to proceed. In a similar fashion, by employing the more active 2 as the catalyst, alkyl and aryl B(C6F5)3-bound nitriles are also successfully reduced and isolated as the corresponding primary amine–borane adducts (Table 1, entries 8–10). In these cases, partial reduction of nitriles to the corresponding imines can not be intercepted or observed. It is noteworthy that the bis-borane adduct of adiponitrile is also fully reduced under similar conditions to give the bis-borane adduct of 1,6diaminohexane (Table 1, entry 10). Attempts to reduce similar B(C6F5)3–isonitrile adducts were unsuccessful. However, catalytic reductive ring opening of an unactivatedN-aryl aziridine functionality is achieved under similar conditions (Table 1, entry 11). [*] P. A. Chase, G. C. Welch, T. Jurca, Prof. Dr. D. W. Stephan Department of Chemistry and Biochemistry University of Windsor Windsor, Ontario, N9B 3P4 (Canada) Fax: (+1)519-973-7098 E-mail: stephan@uwindsor.ca

Complexity in engineering design and manufacturing

Abstract: This paper reviews the breadth of complexity of the design process, products, manufacturing, and business. Manufacturing is facing unprecedented challenges due to increased variety, market volatility and distributed global manufacturing. A fundamental residue of globalization and market uncertainty is the increasing complexity of manufacturing, technological and economic systems. The nature and sources of complexity in these areas are reviewed and complexity modeling and management approaches are discussed. Enterprises that can mitigate the negative aspects of complexity while managing its positives should thrive on the continuous change and increasing complexity. To reap these benefits in the future, manufacturing companies need to not only adopt flexible technical solutions but must also effectively innovate and manage complex socio-technical systems.

A Short Review of Techniques for Phenol Removal from Wastewater

Abstract: Phenolic compounds are priority pollutants with high toxicity even at low concentrations. In this review, the efficiency of both conventional and advanced treatment methods is discussed. The applicability of these treatments with phenol and some common derivatives is compared. Conventional treatments such as distillation, absorption, extraction, chemical oxidation, and electrochemical oxidation show high efficiencies with various phenolic compounds, while advanced treatments such as Fenton processes, ozonation, wet air oxidation, and photochemical treatment use less chemicals compared to the conventional ones but have high energy costs. Compared to physico-chemical treatment, biological treatment is environmentally friendly and energy saving, but it cannot treat high concentration pollutants. Enzymatic treatment has proven to be the best way to treat various phenolic compounds under mild conditions with different enzymes such as peroxidases, laccases, and tyrosinases. This review covers papers from 2013 through January 2016.