The mechanism of the Stevens rearrangement
Abstract
The influence of solvent viscosity and reaction temperature upon the stereoselectivity and intramolecularity of the Stevens [1,2] rearrangement of the ylide (1) has been examined; the results are compatible with two possible mechanisms: (i) a radical pair mechanism with an average geminate recombination rate which is exceptionally fast, or (ii) dual pathways involving concurrent radical pair and concerted processes.