The use of optically active compounds in the isomerisation of ethers and the interchange reaction of nitriles

• Main Author: Wotton, David Edward Mudge
• Published: University of Surrey 1960
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.751554

Benzyl methyl ether rearranges to l-phenyl-ethanol, under the influence of Lewis bases, such as phenyl lithium. This is one of the saturated electrophilic rearrangements which are named after Wittig. An investigation of the ether rearrangement was undertaken using optically active compounds, because the mechanism of the closely allied Stevens rearrangement has been successfully studied in this way. The thesis describes the preparation of benzyl, l-phenyl-propan-l-yl, ether and its successful rearrangement to 1,2-diphenylbutan-l-ol. The preparation and rearrangement of the optically active ether then follows. The results support the propositions of earlier workers, but some aspects of the mechanism remain obscure - especially the movement of the metal atom. An alternative approach to the problem is therefore suggested. In the previous reaction, an optically active group moved on to an inactive centre and its route was deduced. In the proposed experiment an optically inactive group would move onto an asymmetric carbon atom, thus showing the route of the metal atom. The complete mechanism of the reaction would then be demonstrated. Several attempts were made to allow ethers of this type to rearrange, but none were successful. In the second section, the resolution of l-phenyl-propan-l-ol (the ether required for the preparation of benzyl-,l-phenyl-propyl ether) is described. l-phenyl-propyl hydrogen phthalate was first prepared and then resolved by means of its quinidine and strychnine salts. On decomposition of the salts, and hydrolysis of the resulting (+)- and (-)-hydrogen phthalates, samples of ( + )- and (-)-l-phenylpropan-l-ol were obtained with the same rotatory power as those obtained by Pickard and Kenyon, by another method, nearly 50 years ago. In. the third section, the Williamson synthesis of ethers is discussed. Previous experiments by other workers had suggested that ethers prepared by this synthesis from optically pure alcohols should be optically pure, and some experiments described in the section support this supposition. However, other experiments have yielded anomalous results, and these are discussed.