(2,2-Dimethylcyclopropyl)carbinyl Grignard Reagents and the Reactivity of Osmium Tetraoxide and Peroxycarboxylic Acids with Low Valent Iridium Compounds

Citation

Audett, Jay Douglas (1984) (2,2-Dimethylcyclopropyl)carbinyl Grignard Reagents and the Reactivity of Osmium Tetraoxide and Peroxycarboxylic Acids with Low Valent Iridium Compounds. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/z4g9-cb82. https://resolver.caltech.edu/CaltechTHESIS:11122018-101217195

Abstract

The formation and rearrangement of Grignard reagents from (2,2-dimethylcyclopropyl)carbinyl halide have been studied. The Grignard reagent from the chloride, 2,2-dimethyl-3-butenyl-1-magnesium chloride, demonstrates the carbanionic influence on the Grignard rearrangement. The bromide yielded no Grignard reagents, only the disproportionated hydrocarbons 4-methyl-1-pentene and 2-methyl-1,4-pentadiene. The dominating radical side reactions for the bromide may be attributed to the weaker carbon-bromine bond which gives rise to complete bond rupture accompanying single-electron transfer from magnesium.

The reactions of several oxidizing agents with Vaska's complex and its derivatives have been investigated. Interesting results with osmium tetraoxide and peroxycarboxylic acids are described. Osmium tetraoxide reacts with Vaska's complex in the presence of pyridine to form a dinuclear, bridging carbon dioxide complex. Characterization is accomplished with ¹³C,³¹P, and ¹H NMR, in addition to infrared labeling studies. Derivatization of this complex with methyl trifluoromethanesulfonate resulted in amethylation of the carbon dioxide moiety giving the structurally characterized dinuclear carbene complex. The reaction of peroxycarboxylic acids with Vaska's complex under a variety of conditions has yielded a series of compounds. When Vaska's complex is exposed to at least two equivalents of peroxycarboxy lie acid, carbon monoxide is oxidized to carbon dioxide and the iridium product is chlorobis(m- chlorobenzoato)bis(triphenylphosphine)-iridium(III). When the reaction is performed in the presence of excess tetrafluoroboric acid, carbon monoxide oxidation is prevented and the observed product is chloro(m-chlorobenzoato)carbonylbis(triphenylphosphine)iridium(III) tetrafluoroborate. The p-methylbenzoato analogue of this compound has been structurally characterized, and the reactions of nucleophiles with these iridium cations are described. The series of reactions performed with peroxycarboxylic acid suggest a previously unconsidered mechanism for the formation of chlorobis(m-chlorobenzoato)bis(triphenylphosphine)iridium(III) from Vaska's complex and the peroxycarboxylic acid.

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