Catalyst-Free Synthesis of Aryl Diamines via a Three-Step Reaction Process

The formation of C–N bonds
with aryl amines is one of the
most widely studied reactions in organic chemistry. Despite this,
it is still highly challenging, often requiring expensive, precious
metal-based catalysts. Here we report an easy catalyst-free methodology
for constructing C–N bonds. The method, which proceeds via
the in situ formation of closed ring amidinium ions, allows the preparation
of a series of symmetrical and/or unsymmetrical aryl diamines in notably
high yields (82–98%) and purity and with a variety of different
substituents. The methodology is shown successful for the preparation
of aryl diamines having para- and/or meta-substituted carboxyl, nitro, bromo, methoxy, or methyl groups. This
green synthetic pathway, which is catalyst free, requires only three
steps, and proceeds without the need for purification. Further, it
is a new sustainable, economically viable method to achieve an otherwise
challenging bond formation.