Molecular complexes of 4-nitropyridine and 4-nitroquinoline N-oxides with boron trifluoride and hydrogen chloride as intermediates in SNAr reactions

Complexation of 4-nitropyridine N -oxides with ν - (BF 3 , HCl) and π-acceptors (tetracyanoethylene, chloranil, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, 7,7,8,8-tetracyanoquinodimethane) activates the nitro group to nucleophilic replacement by chlorine. Adducts formed by 4-nitropyridine and 4-nitroquinoline N -oxides with boron trifluoride and hydrogen chloride were studied by IR spectroscopy. It was shown that these complexes belong to the n , ν type and that the donor-acceptor interaction therein involves the oxygen atom of the N -oxide group.