I. Low Temperature Deoxygenation Reactions Involving Dihalophosphites. II. The Mechanism of Nucleophilic Substitution at Phosphorus : Evidence for an SNl(P) Mechanism
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Doctor of Philosophy (PhD)
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Part 1: An intermediate species in the Arbuzov ring opening of bicyclic phosphites was discovered. Addition of chlorine or bromine to l-alkyl-4-phospha-3, 5, 8-trioxabicyclo(2. 2.2) and octane at low temperatures produced a solid P, P-dihalo phosphonium intermediate which ring-opened at room temperature to form the 5-alkyl-5-halomethyl-2-halo-2-oxo-1, 3, 2-dioxaphosphorinan. The intermediate was found to deoxygenate alcohols, ethers, aldehydes and ketones to produce the bicyclic phosphate and the various alkyl halides. The intermediate also cleaved acids and esters to form the acyl halides. The mechanism of the deoxygenation reaction was proposed to involve a type of SNi pathway that included the collapse of a pentacovalent phosphorus intermediate. Part 2: A system which may shed new light on the chemistry of nucleophilic substitution at phosphorus was investigated. Three isomeric 5-methyl-5-chloromethyl-2-oxo-2-alkylamino-1, 3,2 dioxaphosphorinans were synthesized from l-methyl-4-phospha-3, 5,8-trioxabicyclo(2. 2. 2)octane.
Methanolysis of the trans-5-methyl-5-chloromethyl-2-oxo-2- chloro-1, 3, 2-dioxaphosphorinan produced two isomeric easters, and is proposed to have proceeded via an SN1(P) mechanism involving a phosphoryl cation intermediate. The kinetics of the methanolysis reaction of the chlorophosphorinan of the methyl ester was found to produce an amine salt of the acid together with the N-methyl amine. The reactions which were investigated should increase our understanding of the chemistry of phosphorus esters and their derivatives. These types of compounds are important in biological systems such as ATP and ADP.
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South Dakota State University
Horten, Henry Liland, "I. Low Temperature Deoxygenation Reactions Involving Dihalophosphites. II. The Mechanism of Nucleophilic Substitution at Phosphorus : Evidence for an SNl(P) Mechanism" (1970). Electronic Theses and Dissertations. 5160.