Browsing by Author "Brownsey, Duncan K."

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    Beyond geminal diesters: increasing the scope of metal-mediated vinylcyclopropane annulations while decreasing pre-activation
    (2018-01) Brownsey, Duncan K.; Gorobets, Evgueni; Derksen, Darren J.
    The utilization of unactivated substrates in annulation reactions provides access to complex products without the need for subsequent removal of the activating group. Vinylcyclopropanes (VCPs), occurring naturally in several monoterpene natural products, are an important building block for organic chemistry, and can be activated by electron withdrawing substituents directly on the cyclopropane to facilitate ring opening reactions. However, many VCPs that lack these activated groups remain reactive with several group 8, 9 and 10 transition metals, by alternative modes of activation, forming metallacycles. These useful intermediates produce annulation products in reactions with unsaturated π-units, providing rapid access to new carbocycles. Several formal cycloadditions that incorporate unactivated VCPs as substrates have been developed, including [5 + 2], [5 + 2 + 1], [5 + 1 + 2 + 1], [3 + 2], [3 + 2 + 1], [5 + 1], and others, using Rh, Ni, Ru, Ir, Fe and Co based catalysts. Mono- and polycyclic ring systems have been made using these methods with their utility demonstrated through the synthesis of complex natural products. This review will summarize the annulations of VCPs that lack geminal diesters, but retain reactivity via transition metal catalysts.
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    Emissions of C9 – C16 hydrocarbons from kelp species on Vancouver Island: Alaria marginata (winged kelp) and Nereocystis luetkeana (bull kelp) as an atmospheric source of limonene
    (Elsevier, 2019-01-24) Tokarek, Travis W.; Brownsey, Duncan K.; Jordan, Nick; Garner, Natasha M.; Ye, Connie Z.; Osthoff, Hans D.
    In this paper, measurements of C9 – C16 biogenic volatile organic compounds (BVOCs) in the headspaces above near-shore marine vegetation samples of Fucus gardneri (rock weed), Ulva spp. (sea lettuce), Callophyllis spp. (red sea fans), Alaria marginata (winged kelp), and Nereocystis luetkeana (bull kelp) collected on the west coast of Vancouver Island, British Columbia, Canada, are presented. Numerous BVOCs were observed in the headspace samples, including n-alkanes (e.g., n-dodecane, n-tridecane, n-tetradecane and n-pentadecane) and oxygenated hydrocarbons (e.g., octanal, nonanal, geranyl acetone, and 6-methyl-hepten-2-one), though the majority of VOCs emitted was not identified. The emissions from Ulva spp., Callophyllis spp. and F. gardneri samples contained a similar assortment of n-alkanes and oxygenated BVOCs (e.g., n-aldehydes) as observed at Mace Head, Ireland, whereas the headspaces above N. luetkeana and A. marginata contained monoterpenes, foremost limonene, and toluene. Further studies are needed to constrain emissions of BVOCs from near-coastal vegetation as they have the potential to substantially impact coastal O3 budgets and the organic content of marine derived aerosol.
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    Principal component analysis of summertime ground site measurements in the Athabasca oil sands with a focus on analytically unresolved intermediate-volatility organic compounds
    (European Geosciences Union, 2018-12-14) Tokarek, Travis W.; Odame-Ankrah, Charles A.; Huo, Jennifer A.; McLaren, Robert; Lee, Alex K. Y.; Adam, Max G.; Willis, Megan D.; Abbatt, Jonathan P. D.; Mihele, Cristian; Darlington, Andrea; Mittermeier, Richard L.; Strawbridge, Kevin; Hayden, Katherine L.; Olfert, Jason S.; Schnitzler, Elijah G.; Brownsey, Duncan K.; Assad, Faisal V.; Wentworth, Gregory R.; Tevlin, Alex G.; Worthy, Douglas E. J.; Li, Shao-Meng; Liggio, John; Brook, Jeffrey R.; Osthoff, Hans D.
    In this paper, measurements of air pollutants made at a ground site near Fort McKay in the Athabasca oil sands region as part of a multi-platform campaign in the summer of 2013 are presented. The observations included measurements of selected volatile organic compounds (VOCs) by a gas chromatograph–ion trap mass spectrometer (GC-ITMS). This instrument observed a large, analytically unresolved hydrocarbon peak (with a retention index between 1100 and 1700) associated with intermediate-volatility organic compounds (IVOCs). However, the activities or processes that contribute to the release of these IVOCs in the oil sands region remain unclear. Principal component analysis (PCA) with varimax rotation was applied to elucidate major source types impacting the sampling site in the summer of 2013. The analysis included 28 variables, including concentrations of total odd nitrogen (NOy), carbon dioxide (CO2), methane (CH4), ammonia (NH3), carbon monoxide (CO), sulfur dioxide (SO2), total reduced-sulfur compounds (TRSs), speciated monoterpenes (including α- and β-pinene and limonene), particle volume calculated from measured size distributions of particles less than 10 and 1 µm in diameter (PM10−1 and PM1), particle-surface-bound polycyclic aromatic hydrocarbons (pPAHs), and aerosol mass spectrometer composition measurements, including refractory black carbon (rBC) and organic aerosol components. The PCA was complemented by bivariate polar plots showing the joint wind speed and direction dependence of air pollutant concentrations to illustrate the spatial distribution of sources in the area. Using the 95 % cumulative percentage of variance criterion, 10 components were identified and categorized by source type. These included emissions by wet tailing ponds, vegetation, open pit mining operations, upgrader facilities, and surface dust. Three components correlated with IVOCs, with the largest associated with surface mining and likely caused by the unearthing and processing of raw bitumen.