Mechanism of the Stevens rearrangement of ammonium ylides

Abstract

Isomerization of trimethylammonium N-benzylide 2 failed to occur at room temperature in a non-basic medium (HMPA) or at -78 °C in the presence of butyllithium in THF. However, N,N-dimethyl-1-phenylethylamine 4 (Stevens rearrangement product) was formed when the temperature of the latter reaction was raised to room temperature. The mechanism of the Stevens rearrangement is discussed.