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Tautomeric perferences in solution and crystaline state of new ylidenemalonodinitrile, fungicidal species precursor.

Jacek M. Grochowski 1Paweł Serda 1Michał Markiewicz 1Bartłomiej Kozik 2Janusz J. Sepioł 2

1. Jagiellonian University, Regional Laboratory of Physicochemical Analysis and Structural Research (REG LAB UJ), Ingadena 3, Kraków 30-060, Poland
2. Jagiellonian University, Departament of Organic Chemistry (Org.Chem, UJ), Ingadena 3, Kraków 30-060, Poland


Some aromatic, vicinal aminonitriles exhibit strong fungicidal properties against selected tested fungi [1]. This encouraged us to search for easily synthesized carbocyclic, aromatic aminonitriles. Using the Knoevenagel condensation of 2,2-bis(4-chlorophenyl)acetaldehyde with malonodinitrile and chromatographic purification, a slowly solidifying oily product was obtained. NMR spectra recorded in CDCl3 revealed presence of two tautomeric forms which arose through the migration of the carbon-carbon double bond. The ratio of the expected tautomer (3,3-bis(4-chlorophenyl)-1-propene-1,1-dicarbonitrile) and the second tautomer (3,3-bis(4-chlorophenyl)-2-propene-1,1-dicarbonitrile) was estimated from 1H NMR spectrum as 3.8:1. The former is a precursor for 1-amino-4-(4-chlorophenyl)-naphthalene-2-carbonitrile which belongs to a group of compounds with proven fungicidal acitivity. Analytical sample of ylidenemalonodinitrile was recrystallized from petroleum ether (bp: 60-90oC) affording yellowish crystals, mp 101.5-103.5oC, monoclinic system, space group P21/c, lattice parameters a=13.8905(9), b=7.7323(4), c=14.335(1) A, β=93.846(2) o. The structure was solved by direct methods and refined using full-matrix LSQ procedure. All hydrogen atoms were located on the difference Fourier map of electron density.
Both the hydrogen atom position bonded to the carbon coordinating two chlorophenyl groups and the double bond position indicated univocally the presence of solely tautomer 1 in the crystalline phase.
The energy calculations for both tautomers were carried out in order to find the most stable conformer for each tautomer and then compare their energy values to prove which tautomer is energetically preferred. The resulting energy differences are rather low indicating that both tautomers are energetically equivalent in vacuum.

[1] J. Wilamowski, E. Kulig, J.J. Sepiol, Z.J. Burgiel, Pest Manag. Sci. 57 (2001) 625.


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Presentation: poster at E-MRS Fall Meeting 2003, Symposium B, by Jacek M. Grochowski
See On-line Journal of E-MRS Fall Meeting 2003

Submitted: 2003-07-10 13:48
Revised:   2009-06-08 12:55