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Diastereoselective Synthesis of Seven-Membered Ring trans-Alkenes and Development of Stereospecific Nickel-Catalyzed Cross-Coupling Reactions

Posted on:2014-05-21Degree:Ph.DType:Dissertation
University:University of California, IrvineCandidate:Greene, Margaret AFull Text:PDF
GTID:1451390005999478Subject:Chemistry
Abstract/Summary:
The understanding of the reactivity of strained silacyclopropanes has been expanded to include the reactivity of vinylsilacyclopropanes, formed by silylene transfer to a 1,3-diene. The reactivity of vinylsilacyclopropane with carbonyl compounds has been explored and is shown to yield trans -oxasilacycloheptenes. trans-Oxasilacycloheptenes are formed stereoselectively as a result of carbonyl insertion through allylic transposition. trans-Oxasilacycloheptene is a highly strained compound that exhibits elevated reactivity. trans-Oxasilacycloheptene rearranges at room temperature to vinyloxasilacyclopentane by a 1,3-silyl migration. trans-Oxasilacycloheptene has been trapped by a variety of methods.;Adapting conditions established in the Jarvo laboratory for stereospecific nickel-catalyzed cross-coupling of naphthylic ethers with methyl Grignard reagent, work is presented which expands the scope of these reactions to include benzylic ethers. A traceless directing group is employed to facilitate the coupling of this challenging class of substrates. This method is shown to increase the reactivity of benzylic ethers, which is proposed to occur by magnesium salt coordination to the directing group. The reaction proceeds with excellent transfer of stereochemical information.;The mechanism of nickel-catalyzed Kumada cross-coupling of naphthylic ethers with methyl Grignard reagent has been studied. The reaction is first order in electrophile, catalyst, and magnesium iodide. The rate of the reaction shows no dependence on methyl magnesium iodide. Competition experiments demonstrate the importance of the traceless directing group for the coupling of benzylic ethers.;A method has been developed for the stereospecific nickel-catalyzed cross-coupling of naphthylic carbamates with aryl boronic esters. Products with retention or inversion can be formed from the same enantiomer of starting material with proper choice of an achiral catalyst. Phosphine ligand provides product with retention and N-heterocyclic carbene ligand provides products with inversion at the electrophilic carbon.
Keywords/Search Tags:Stereospecific nickel-catalyzed cross-coupling, Reactivity, Reaction
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