An Unusual Rearrangement and its Dependence on Configuration

Abstract

In the course of a synthetic study, we encountered an unusual rearrangement that we now report, one that involves a 5-nitronorbornenyl system having 7-endo- and 7-exo-pyridin-2-yl groups being treated under Nef-reaction conditions. The stereoisomers differ in their Nef-reaction behavior: the isomer with the pyridin-2-yl group exo to the NO2 moiety primarily affords the Nef reaction, however, with formation of a rather unusual rearrangement side-product. The endo-pyridyl stereoisomer proceeded exclusively with rearrangement.