28 research outputs found

    A One-Pot Tandem Olefin Isomerization/Metathesis-Coupling (ISOMET) Reaction

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    A tandem catalytic reaction has been developed as part of a process to discover tungsten-based olefin metathesis catalysts that have a strong preference for terminal olefins over cis or trans internal isomers in olefin metathesis. This tandem isomerization/terminal olefin metathesis reaction (ISOMET) converts C[subscript n] trans internal olefins into C[subscript 2n–2] cis olefins and ethylene. This reaction is made possible with Ru-based “alkene zipper” catalysts, which selectively isomerize trans olefins to an equilibrium mixture of trans and terminal olefins, plus tungsten-based metathesis catalysts that react relatively selectively with terminal olefins to give Z homocoupled products. The most effective catalysts are W(NAr)(C[subscript 3]H[subscript 6])(pyr)(OHIPT) (Ar = 2,6-diisopropylphenyl; pyr = pyrrolide; OHIPT = O-2,6-(2,4,6-i-Pr[subscript 3]C[subscript 6]H[subscript 2])[subscript 2]C[subscript 6]H[subscript 3]) and various [CpRu(P–N)(MeCN)]X (X[superscript –] = [B(3,5-(CF[subscript 3])[subscript 2]C[subscript 6]H[subscript 3])[subscript 4][superscript –]], PF[subscript 6][superscript –], B(C[subscript 6]F[subscript 5])[subscript 4][superscript –]) isomerization catalysts.National Science Foundation (U.S.). Center for Chemical Innovation. Center for Enabling New technologies through Catalysis (Phase II Renewal. CHE-120518)National Science Foundation (U.S.) (CHE-1059107

    Update of the 2014 Drought on California Rangelands

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    On the Ground • Droughts are common on California rangelands. • The current drought in California is listed as severe or exceptional for most of the state. • The drought has affected rangeland, and the livestock industry, more than other commodities. • The actual costs associated with this drought are just beginning to be realized.The Rangelands archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform March 202
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