Migratory aptitudes

Migratory aptitude roughly follows the ability of the group to stabilize positive charge ... 

Examination of the migratory aptitude of groups in a variety of unsym-metrical ketones indicates that the group best able to accept a positive charge will usually migrate most readily. ... 

From the data eolleeted in Table VII, it follows that the migratory aptitude of the Si-, Ge-, and Sn-eentered groups in the rearrangement 40a 40b inereases from SiRj to SnRj groups. 

The reaction is facilitated when R is electron withdrawing, when R has a high migratory aptitude (ability to stabilize a carbonium ion), and by polar reaction media. 

The carbocations generated by non-Kolbe electrolysis can rearrange by alkyl, phenyl or oxygen migration. The migratory aptitudes of different alkyl groups have been studied in the rearrangement of a-hydroxy carboxylic acids (Eq. 34) [323]. 

Migratory aptitude vinyl > iso-propyl > cyclopropyl > benzyl... 

With unsymmetrical cyclic ketones, however, mixtures due to similar migratory aptitudes of the different groups are obtained (Table 13, Nos. 2, 3). The rearrangement has also been used as key step in a d,/-muscone synthesis (Table 13, No. 4). 

In order to answer the question about inherent migratory aptitudes, the obvious type of substrate to use (in the pinacol rearrangement) is R RC—CRR since the... 

Migratory aptitudes have been measured for the phenyl and vinyl groups, and for... 

It has been shown that methyl and phenyl have lower migratory aptitudes than hydrogen in thermal sigmatropic rearrangements Shen, K. McEwen, W.E. Wolf, A.P. Tetrahedron Lett., 1969, 827 Miller, L.L. Greisinger, R. Boyer, R.F. J. Am. Chem. Soc., 1969, 91, 1578. 

---