(1) the use of Nitrosoalkenes, Vinylnitrosonium cations, and Nitroalkenes in Heterodiene (4+2); Cycloadditions. (2) Experimental, spectroscopic, and theoretical investigations of Phosphorus (V) stabilized Allyl anions

Cramer, Christopher John

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Title

(1) the use of Nitrosoalkenes, Vinylnitrosonium cations, and Nitroalkenes in Heterodiene (4+2); Cycloadditions. (2) Experimental, spectroscopic, and theoretical investigations of Phosphorus (V) stabilized Allyl anions

Author(s)

Cramer, Christopher John

Issue Date

1988

Department of Study

Chemistry

Discipline

Chemistry

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Chemistry, Organic
• Chemistry, Physical

Abstract

• 1. (4+2) -Cycloadditions of nitrosoalkenes, vinylnitrosonium cations, and nitroalkenes are discussed.
• The silyloxime of an $\alpha$-chloroalkylphenylketone produced a nitrosoalkene which cyclized intramolecularly with an unactivated olefin. Cycloaddition was stereospecific for a trans-fused product via an exo transition state.
• $\alpha{,}\beta$-Epoxyaldonitrones were prepared in high yields and transformed into vinylnitrosonium cations which underwent intramolecular cyclization with unactivated olefins upon treatment with trimethylsilyl trifluoromethane-sulfonate. VT-NMR indicated cycloaddition to occur at $-30\sp\circ$C. The cycloadditions were stereoselective, forming products via a parallel, exo transition state.
• Both intra- and intermolecular cycloadditions of nitroalkenes with unactivated olefins under Lewis-acid catalysis were investigated. Tin tetrachloride was the Lewis acid of choice. VT-NMR studies were done on the nitroalkene/tin tetrachloride complex. The equilibrium thermodynamic parameters for complexation were determined in two solvents. The complex was 1:1 in stoichiometry. The intramolecular cycloadditions were found to be stereospecific with both (E)-and (Z)-trisubstituted nitroalkenes. Intermolecular cycloadditions were found to proceed efficiently and stereoselectively with 1-nitrocyclohexene. Elaboration of the cycloadducts was investigated, including their use as 1,3-dipoles in (3+2) -cycloadditions, and their cleavage to afford hydroxy ketones or derivatives thereof.
• 2. Anions derived from allyl phosphonic diamides were examined for their $\alpha/\gamma$-selectivites upon substitution with alkyl halides/sulfates, carbonyl compounds, enones, and trialkylsilyl chlorides. Selectivities were strongly dependent on electrophile, bulk of the phosphonic diamide, and allylic substitution.
• NMR indicated phosphorus-(V)-stabilized, allyl anions in ethereal and hydrocarbon solvents to be mixtures of probably monomeric (E)- and (Z)-isomers with the (E)-isomer predominating. The carbon bearing phosphorus was shown to undergo substantial sp$\sp3$ $\to$ sp$\sp2$ rehybridization upon anion formation.
• Large-basis-set, well-correlated, ab initio calculations were performed on phosphine oxide and phosphinous acid. The difference in equilibrium stabilities was 2.8 kcal/mole and the barrier to unimolecular rearrangement was 68 kcal/mole. Allyl phosphonic diamide was studied at the 3-21G(*) level as a neutral, free-anionic, and lithiated species. The free anion was found to exist in both (E)- and (Z)-forms with a planar allylic $\pi$ system eclipsing the P-O bond. Inclusion of lithium distorted the allyl system and changed the relative energy from favoring E to Z. In both isomers the lithium atom made both oxygen and carbon contacts. Anions showed highly ionic bonding and charge localization. Mulliken populations were consistent with spectroscopic results and isomer assignments.

Graduation Semester

1988

Type of Resource

text

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