Reactions of Tris(trimethylsilyl)silyl Radicals with Nitroalkanes. EPR, Kinetic, and Product Studies

Authors:

• Marco Ballestri,
• Chryssostomos Chatgilialoglu,
• Marco Lucarini,
• Gian Franco Pedulli

Abstract

The radical-initiated reaction of tris(trimethylsilyl)silane with a variety of aliphatic nitro derivatives has been investigated. This silane, which for many applications is a valid alternative to tributyltin hydride, is unable to reduce tertiary nitroalkanes to the corresponding hydrocarbons. EPR results, as well as kinetic and products studies, have shown that this “anomalous” behavior is due to the fact that the nitroxide adducts formed by addition of tris(trimethylsilyl)silyl radicals to the nitro compounds fragment preferentially at the nitrogen-oxygen bond rather than at the carbon-nitrogen bond as in the analogous tributyltin adducts. The resulting silyloxy radical, (MegSi)₃SiO•, undergoes a fast rearrangement (k ≥ 10⁷ s^-1 at room temperature) with migration of a Me₃Si group from silicon to oxygen to give (Me₃Si)₂SiOSiMe₃ which adds to the nitro compound affording a secondary nitroxide adduct. The kinetics of the decay of both primary and secondary adducts to nitromethane has been studied over a wide range of temperatures. With tertiary nitroalkanes persistent aminyl radicals, RNOSi(SiMe₃)₃, have also been detected. © 1992, American Chemical Society. All rights reserved.