Heterocycles from dinitriles

Without additional reagents o-Amino-o -halogeno-N-heterocyclics from dinitriles... 

Selectivity decreases when the chain length of dinitriles increases from six to ten carbon atoms per molecule, but this relationship levels off at each extreme of the range. We propose to explain this observation by invoking an intramolecular interaction leading to a heterocyclic (n+1) conformation, containing imino- form of the CN, in equilibrium with the linear form. Hence, for example, for the five carbon system ... 

High selectivity to aminonitriles can be achieved when hydrogenation of dinitriles containing from 5 to 12 carbon atoms per molecule over Raney catalysts as Ni/CrFe, and Ni/Mo is carried out, at moderate conditions of temperature and pressure, in solvents such as MeOH + NaOH, or in liquid ammonia. Observed dependence of selectivity on the carbon chain length can be explained by an equilibrium between linear and heterocyclic forms of aminonitriles. 

When some heterocyclic dicarboxylic anhydrides are heated in contact with a glowing nichrome wire, the dinitrile is formed [167] probably via a heteryne, for example, o-phthalonitrile was obtained in 72% yield from quinoxaline-2,3-dicarboxylic anhydride. 

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