Dipolar Additions with 1-(6-Chloropyridazin-3-yl)pyridinium-3-olate and 1,1′-(Pyridazine-3,6-diyl)di(pyridinium-3-olate)

Abstract

The regio- and stereo-selectivities of the cycloadditions of the title pyridinium-3-olates at the 2- and 6-positions with mono- and di-substituted alkenes are elucidated and rationalised, including secondary orbital overlap and taking into account steric and dipolar effects: for electron-acceptor and conjugated alkenes, all add in the same regioselective sense, with the stereoselectivity being shown to depend on the structure of the pyridinium-3-olate and the addend.