IRREVERSIBLE REARRANGEMENT OF SILYL GROUPS BETWEEN OXYGEN AND NITROGEN IN TRIS(SILYL)HYDROXYLAMINES

Diorganofluorosilylation of 1,2-bis(trimethylsilyl)hydroxylamines at l ow temperatures gives exclusively fluorosilyl)-N,N-bis(trimethylsilyl) hydroxylamines 1a,b. The thermal rearrangement of 1a,b to the isomeric fluorosilyl)-N,O-bis(trimethylsilyl)hydroxylamines 2a,b is found to b e irreversible, and the experimental data suggest an intramolecular co urse of the isomerization. Ab initio and density functional calculatio ns for model compounds demonstrate the dyotropic course of the rearran gement. Anomeric stabilization of 2a,b by more favorable negative F-Si -N and O-Si-C hyperconjugation is important for the irreversibility of the reaction.