1,3-dipolar [3+2] cycloaddition of N-alpha-diphenyl nitrone to the benzene ligand in reductively activated [Mn(CO)(3)(eta(4)-C6H6)](-)

摘要

We have established that the eta(4)-benzene ligand in [Mn(CO)(3)(eta(4)-C6H6)](-) undergoes a stepwise cycloaddition reaction with N-alpha-diphenyl nitrone in a sequence in which the Lewis acid BF3 is first used to induce nucleophilic addition of [Mn(CO)(3)(eta(4)-C6H6)](-) to N-alpha-diphenyl nitrone. The BF3 can be removed by protonation to give the neutral intermediate [Mn(CO)(3)-{eta(5)-C6H6CHPhN(Ph)OH}], which can be cyclized by addition of excess KH and PPNCl to drive ring closure and form PPN[Mn(CO)(3){eta(4)-C6H6{CHPhN(Ph)O}], containing an isoxazolidine ligand that is the [3 + 2] cycloaddition product of the nitrone with benzene. [References: 24]