Oxidative primary amines with isocyanides

Oxidative Addition Reactions of Primary Amines with Isocyanides... 

Unsymmetrical carbodiimides. Isocyanides react with primary amines under catalysis of NiCh. Air is the oxidant. 

Formally, carbodiimides may be generated by the addition of a (nucleophilic) primary amine to an isocyanide (with an electron deficiency see constitutional formula 1515b and considerations on isocyanides in the introduction to Section 4.5.2) under release of a reduction equivalent (two electrons) and two protons. The required oxidation equivalent can be provided most easily with an oxygen atom. 

Reaction of isocyanides with primary amines in the presence of selenium and DBU, followed by the introduction of molecular oxygen in refluxing THF, affords unsymmetrical and symmetrical carbodiimides in isolated yields of 58-87% [1282] (see also Section 4.5.3.5, Table 4.48). The oxidation reaction is mediated by selenium with the assistance of base DBU. 

N,N -disubstituted carbodiimides are synthesized from the reaction of isocyanides with primary amines in the presence of a Ni(II) catalyst using oxygen as the oxidant [261]. 

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