- Molybdenum chloride catalysts for Z-selective olefin metathesis reactions
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The development of catalyst-controlled stereoselective olefin metathesis processes has been a pivotal recent advance in chemistry. The incorporation of appropriate ligands within complexes based on molybdenum, tungsten and ruthenium has led to reactivity and selectivity levels that were previously inaccessible. Here we show that molybdenum monoaryloxide chloride complexes furnish higher-energy (Z) isomers of trifluoromethyl-substituted alkenes through cross-metathesis reactions with the commercially available, inexpensive and typically inert Z-1,1,1,4,4,4-hexafluoro-2-butene. Furthermore, otherwise inefficient and non-stereoselective transformations with Z-1,2-dichloroethene and 1,2-dibromoethene can be effected with substantially improved efficiency and Z selectivity. The use of such molybdenum monoaryloxide chloride complexes enables the synthesis of representative biologically active molecules and trifluoromethyl analogues of medicinally relevant compounds. The origins of the activity and selectivity levels observed, which contradict previously proposed principles, are elucidated with the aid of density functional theory calculations.
- Koh, Ming Joo,Nguyen, Thach T.,Lam, Jonathan K.,Torker, Sebastian,Hyvl, Jakub,Schrock, Richard R.,Hoveyda, Amir H.
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- Substituent effects on the disproportionation-combination rate constant ratios for gas-phase halocarbon radicals, Part 5: Reactions of CF3 + CF3CH2CHCH3 and CF3CH2CHCH3 + CF
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Rate constant ratios, kd/kc for the disproportionation/combination reaction have been measured as 0.07 ± 0.02 when an H is removed from the CH2 position of the CF3CH2CHCH3 radical and as 0.
- Ferguson Bert E Holmes, John D.
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p. 549 - 557
(2007/10/03)
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