Synthetic And Mechanistic Studies In Oxime And Amide Chemistry

Abstract

The thesis entitled “Synthetic and Mechanistic Studies in Oxime and Amide Chemistry” consists of two chapters. Chapter 1 contains 3 parts, dealing with the Beckmann rearrangement under solvent free conditions, Mitsunobu conditions, and with catalytic succinic anhydride-ZnCl2. Chapter 2 deals with bond length and reactivity studies with several oxime esters. CHAPTER 1 Part 1: This describes studies aimed at the development of the Beckmann rearrangement in the solid state using phenylboronic acid. The adsorption of ketoximes on a mixture of phenylboronic acid and neutral alumina followed by heating >120 °C, afforded the expected amides, although with competing hydrolysis to corresponding ketones. It appeared that phenylboronic acid was being converted under the reaction conditions to triphenyl boroxine, which was presumably the active species effecting the Beckmann rearrangement. This was experimentally confirmed when the amide products were obtained in good yields when the reaction was performed with triphenyl boroxine. Part 2: This describes the Beckmann rearrangement under Mitsunobu conditions. Triphenyl phosphine and diethyl azodicarboxylate can react with various oximes to produce corresponding amides. Part 3: This describes the Beckmann rearrangement of oximes to amides by a combination of succinic anhydride and zinc chloride as catalyst. Zinc chloride can activate succinic anhydride, the activated succinic anhydride then reacting with the oximes. This forms the oxime ester of succinic acid, which undergoes the Beckmann rearrangement as shown. CHAPTER 2: This describes bond length and reactivity studies with several oxime esters. It was of interest to obtain a correlation between bond length and reactivity in ketoxime derivatives which are known to undergo the Beckmann rearrangement. Towards this end the crystal structures of a variety of oxime esters have been determined. The results indicate that the alkyl group anti to the oxime hydroxyl group is pre-disposed towards migration onto the nitrogen center. (pl refer the thesis for structural formula)