913638-51-4Relevant academic research and scientific papers
Guanylation of aromatic amines catalyzed by vanadium imido complexes
Montilla, Francisco,Pastor, Antonio,Galindo, Agustín
, p. 993 - 996 (2004)
The reaction of formation of guanidines by coupling of carbodiimides and aromatic amines using imido vanadium complexes as catalyst have been investigated. Results demonstrate that the complex V(N-2,6-iPr2C6H3)
Use of vanadium complexes as catalysts in the synthesis-of guanidines: New experimental data and DFT analysis of the carbodiimide interaction with the catalyst
Montilla, Francisco,Del Rio, Diego,Pastor, Antonio,Galindo, Agustin
, p. 4996 - 5002 (2006)
The activity of several imido vanadium complexes as catalysts of the guanylation reaction was studied. Complex V(N-2,6-iPr 2C6H3)Cl3, 1, was found to be an efficient precatalyst for the reaction between carbodiimides and both primary and secondary aryl amines to give the corresponding guanidines 2-6. Two possible pathways for the reaction were considered for a DFT study: (i) [2+2] carbodiimide addition to the vanadium-imido bond, a mechanism previously ascertained by Richeson and co-workers for the synthesis of guanidines catalyzed by titanium imido compounds (J. Am. Chem. Soc. 2003, 125, 8100); and, alternatively, (ii) carbodiimide insertion into the vanadium-amido bond, which would be formed in situ by the interaction of the amine reagent with 1. First, the titanium-catalyzed reaction, using {(Me2N)C(NMe) 2}2Ti(=NMe) (A) as a model complex, was studied. Second, two different vanadium model complexes, V(=NMe)Cl3 (B) and V(=NMe)(NMe2)Cl2 (C), were considered for the guanylation. Noticeably, whereas for model A the [2+2] carbodiimide addition to the metal-imido bond was an exergonic process, for model B the same pathway was not exergonic and gave a much higher activation barrier than that computed for A. Finally, the two pathways were investigated with model C, containing both imido and amido functionalities. The results show that for vanadium-catalyzed guanylation reactions the carbodiimide insertion into the metal-amido bond is favorable with respect to the carbodiimide addition to the metal-imido bond, which is the mechanism operative for titanium.
