The N-C Rearrangement

Recent investigations by Brook and Duff 3a, 8a) have shown that silicon will rearrange from carbon to nitrogen or vice versa, the direction of migration depending on the particular substituents in the substrate compound. In this the C—N compounds closely resemble the C—O systems described in Section V. 

The first reaction to be described was the catalytic rearrangement of aminomethylsilanes to methylaminosilanes. This proceeds by deprotonation of the amino hydrogen and 1,2-anionic rearrangement followed by reprotonation 3a)  

Studies of NMR spectra in hexane indicate that the position of equilibrium in the anionic rearrangement also depends on phenyl substitution at carbon. Results are given in Eqs. (33-36) 8a). 

The solvent composition also influences the position of equilibrium. Addition of large amounts of THE, or even small amounts of TMEDA, shift the equilibrium in the MeaSiCHPh— NHMe system toward the carbanion. Presumably this effect results from solvation of the lithium cation, which may stabilize the Li+—C relative to the Li — N ion pair. 

The N- C anionic rearrangement is slow enough so that at least for some compounds it can be followed by NMR. A kinetic study of the rearrangement of Eq. (37) showed that the reaction is, as expected, a first-order equilibration. The energies of activation and 

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