N‐Oxides as Control Element for the Direction of a Sigmatropic Rearrangement: Application as a Switch for Fluorescence

Abstract

AbstractAn exceptional level of control over the direction of the (2,3)‐sigmatropic rearrangement between N‐oxides and alkoxylamine is achieved by simply changing the solvent in which they are dissolved. Protic solvents like water, methanol and hexafluoroisopropanol favour the N‐oxide form, while other solvents like acetone, acetonitrile and benzene favour the alkoxylamine. The reaction temperature and nature of the substituents on the alkene affect the rate of rearrangement. A N‐oxide fragment was attached to two fluorescent molecules and acted as an on/off switch for their fluorescence. The conversion of alkoxylamines into the corresponding N‐oxides has not previously been described and is here termed the ‘Reverse Meisenheimer Rearrangement’.