PART I. FACTORS GOVERNING THE REVERSIBLE ADDITION OF ALLYLIC ORGANOMETALLIC REAGENTS TO HINDERED KETONES. PART II. THE CLEAVAGE OF DI-N-BUTYL ETHER BY GRIGNARD REAGENTS. PART III. THE FORMATION OF IODOTRIMETHYLSILANE IN REACTIONS INVOLVING PHENYLTRIMETHYLSILANE - IODINE
Abstract
(I) The solvent and phenyl effects on the rearrangement of hindered homoallylic alkoxides were investigated. Polar or cation solvating solvents were found to enhance the rate of rearrangement. The rearrangement was found to be predominantly intramolecular. The ketone was shown to be produced through its enolate in the very fast rearrangements and was also formed independent of rate. Mechanistic considerations of the rearrangement were discussed. The phenyl effect was determined to be largely a steric effect with minimal contribution from electronic factors. Substitution at the ortho position of the phenyl ring was found to enhance the rate of rearrangement. The addition of crotyl Grignard reagent to hindered ketones was discussed in terms of a pseudo-cyclohexane transition state. The resulting diastereomers were identified and the diastereomeric ratio was subject to change by lowering the temperature of the reaction. (II) The minor product in the coupling reaction of the ethyl Grignard reagent with allyl bromide was reinvestigated. The literature report that it was isopropylethylene was shown to be incorrect. Instead it was shown to be a mixture of 1-pentene and 1-butene, the latter arising from a slight cleavage of the di-n-butyl ether by the ethyl Grignard reagent. (III) The cleavage of phenyltrimethylsilane by iodine was found to proceed faster than previously thought. This fact was used to rationalize the enhanced rate of cleavage of esters by phenyl-trimethylsilane-iodine instead of with iodotrimethylsilane alone. The catalytic effect of iodine in cleavage reactions with iodotrimethylsilane demonstrated by Mozdzen was also shown to be present in the phenyltrimethylsilane-iodine combination. The mechanism of this reaction was discussed.
Degree
Ph.D.
Subject Area
Organic chemistry
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