SILPAKORN UNIVERSITY SCIENCE AND TECHNOLOGY JOURNAL, Vol 1, No 2 (2007)

Recent Development in Alkynol Chemistry: Electrophilic Iodonium-Induced Rearrangements

Pakorn Bovonsombat, Pratheep Khanthapura, Juthamard Leykajarakul








Abstract


Recent development in iodonium-induced reactions of alkynols is discussed and analysed herein. Classical Meyer-Schuster and Rupe rearrangements are described as a background to the main body of iodonium-induced reactions. -Iodoenones derived from rearrangement of alkynols, known herein as the Iodo Meyer-Schuster reaction, links the classical Meyer-Schuster reaction to the novel reaction of iodonium-induced rearrangement of alkynols. The rearrangements leading to the formations of β-haloenones and β,β-dihaloenones and enals are discussed with mechanistic considerations, which include stereospecificity of the migrating group and the migratory aptitude differences between the phenyl and the alkyl groups. The role of solvents – namely the water content in organic solvent – is presented with mechanistic consideration of the role of the allenol, the halonium bridge cation intermediates and water in dictating each different reaction pathways. The application of the rearrangement reaction to biological interesting molecule such as glucofuranose and xylofuranose is discussed. Haloetherification reaction, the third type of halonium-induced alkynol reaction, was found to be the exclusive reaction in the halogenation of alkynol derivative of hexofuranoses.

Key Words: Electrophilic halogenations; alkynols; iodonium ions; Meyer-Schuster and Rupe Rearrangements;β-haloenones; β,β-dihaloenones and enals; ring expansion of alkynols

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