Anti migration

Alternatively, oximes may be converted to O-substituted oximes (typically O-tosyl oximes) making the rearrangement much easier. Sometimes, these oxime derivatives rearrange spontaneously under the condition of their formation and cannot be isolated. Usually, O -tosyl ketoximes rearrange smoothly with exclusive anti migration. Relative to the acid-promoted Beckmann rearrangement, the rearrangement of O -tosyl oximes is much milder and specific. 

Tosyl ketoximes generally rearrange smoothly and with exclusive anti migration whoi dissdved in polar media a typical example is depicted in equation (10). The tosyl derivatives frequently rearrange under the conditions of their formation (equation 11), and the mildness and specificity of diis procedure recommend it for use with acid-sensitive substrates (equation 12). ... 

Cristol, S. J., Opitz, R. J. Photochemical transformations. 40. syn and anti Migration in photo-Wagner-Meerwein rearrangements. J. Org. Chem. 1985, 50, 4558-4563. 

A methylaluminium phenoxide derived from 2,6-di-tert-butyl-4-bromophenol can function as a catalyst in the stereoselective anti-migration of the dimethyl-t-butylsiloxy group in the epoxides illustrated to afford siloxyaldehydes in high yields (ref. 116). 

The sterically unfavorable syn migration is a thermally forbidden [tr, + process. The latter designation was erroneously applied to the anti migration (. ) this does not affect the general conclusions, however. 

Therefore, in order to achieve high conductivity it is necessary to avoid contamination from impurities at all costs, and to maintain high purity. Figure 3M shows the variation in value of resistance when Pd and Au are dissolved in Ag (both Ag-Pd and Ag-Au types are solid solution alloys). As noted below, in the case of Ag conductors, there have been many attempts to make alloys in order to improve anti-migration characteristics, but as shown in the figure, with the Ag-Pd type for example, when Pd is dissolved at 60... 

This result is explained by the preferential interaction of the Lewis add at the less crowded side of the epoxide and subsequent anti migration of the propyl group to generate ketone 150. 

This was completely reversed with the isomeric epoxide. From these results one can draw the conclusion that while alkyl residues prefer the anti-migration, hydrogen... 

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