[1,2]‐Wittig Rearrangement

Abstract

The transformation of an ether into a secondary alkoxide via a [1,2]‐carbon shift by treatment of the ether with a strong base such as alkyl lithium is generally known as the [1,2]‐Wittig rearrangement. Similarly, the analogous transformation of thioether into thiol is called the thio ‐Wittig rearrangement, and the corresponding conversion of imine is known as imino 1,2‐Wittig rearrangement. The driving force for this reaction is the instability of the α‐oxygenated carbanion. The reaction rate has been reported to increase with more base. It has been noticed that the yield of the [1,2]‐Wittig rearrangement is usually low, and the reaction might be complicated by other reactions. It has been found that the [1,2]‐Wittig rearrangement is solvent dependent. In spite of the fact that the [1,2]‐Wittig rearrangement proceeds via homolytic dissociation and the radical recombination mechanism, the stereogenicities of the two proradical centers are retained to appreciable extents. This reaction has limited applications in organic synthesis.