It's well documented that silyl group has a tendency to migrate to the neighboring location as long as the geometry favors the move. During my graduate study, an 1, 4-N to C anionic migration was observed, in which the Me3Si group on the allylic amine nitrogen underwent an intramolecular migration to the vinylic carbon anion generated by transmetallation of Bu3Sn group that has a Z-configuration ( Corriu and Geng et al: J. Org. Chem., 1993, 58 , 1443). In contrast, the N, N-bis(Me3Si)-E-Bu3Sn substituted allylic amine gives no migration upon lithiation, which comfirmed the steric requirement.
A similar 1, 4-N to C anionic migration was recognized by an Italian group a bit earlier (Ricci et al: Synlett., 1991, 712). In this case the allylic anion was produced by deprotonating the allylic C-H in N, N-bis(Me3Si)-E-Me3Si substituted allylic amine. Interestingly, over a decade and half later, these remain as the only two examples of 1, 4-N to C-silyl migration. During the last 20 years, a number of other 1, 4-silyl migrations have been reported, such as, from O to C ( Mitchell et al: Tet. Lett., 1999, 55, 1285; Lautens et al: J. Org. Chem., 1992, 57, 3270), from C to O (Takeda et al: Chem. Commun., 2002, 2218) and from C to C (Kawachi et al: Organometallics, 2006, 25, 2390). All these 1,4-silyl migrations will find more synthetic applications in the future.
A similar 1, 4-N to C anionic migration was recognized by an Italian group a bit earlier (Ricci et al: Synlett., 1991, 712). In this case the allylic anion was produced by deprotonating the allylic C-H in N, N-bis(Me3Si)-E-Me3Si substituted allylic amine. Interestingly, over a decade and half later, these remain as the only two examples of 1, 4-N to C-silyl migration. During the last 20 years, a number of other 1, 4-silyl migrations have been reported, such as, from O to C ( Mitchell et al: Tet. Lett., 1999, 55, 1285; Lautens et al: J. Org. Chem., 1992, 57, 3270), from C to O (Takeda et al: Chem. Commun., 2002, 2218) and from C to C (Kawachi et al: Organometallics, 2006, 25, 2390). All these 1,4-silyl migrations will find more synthetic applications in the future.
