Aim and Objective: A wide variety of synthesized amidine derivatives are bioactive
compounds. They show a vast range of medical properties. Therefore, a simple route for synthesis of
novel class of amidine derivatives called amidino carboxylic acids and their use as catalysts in
Strecker reaction has been reported in the current work. The stability, local charge density and
hydrogen bond parameters were calculated for eight derivatives with different substituents.
Materials and Methods: In order to synthesize these amidino carboxylic acids, we initially prepared
Knovenogel condensation products via the reaction of isatin derivatives with malonitrile. When the
reaction was performed in water, the resulting nitrile groups of malonitrile derivatives was
hydrolyzed with HOAC/ H2SO4 to generate the desired amide groups. The amide groups in resulting
compound converted to amine groups with two Hoffman rearrangements in the presence of
NaOH/Br2. Further neutralization led to the final zwitterionic α-amidino carboxylic acids. In the next
step, the catalytic activity of these compounds as H-bond donor catalyst was investigated in Strecker
Results: The overall yields of the derivatives with substituent on the aromatic ring of starting isatins
are higher than that for the overall yields of nitrogen-substituted isatins. The reaction of 5-nitro isatin
with the next reagent gives lower yield in aryl-substituted products. An increase of catalytic activity
is observed by rising the electron-withdrawing power of the aromatic ring substituents., The
presence of nitro group in the structure of catalyst caused a large increase of catalytic activity in
Strecker reaction. DFT calculations at B3LYP/6-31++g(d,p) and Lanl2dz level of theory showed that
these compounds act as single H-bond catalysts and higher yields were obtained for complexes with
stronger hydrogen bond.
Conclusion: A simple and efficient method for synthesis of ɑ-amidino carboxylic acids was
developed in this research. These compounds have been used as a single H-bond donor catalyst in
the Strecker reaction. DFT calculations were carried out to confirm the experimental results. The
obtained data from computations are in good agreement with experimental results.