Reactivity of (E)-4-aryl-4-oxo-2-butenoic acid phenylamides
and washed with few drops of Et2O, then dried in air.
Yield: 96.5 %; white solid; m.p.: 82–83 °C (Et2O/hexane);
1H NMR (CDCl3, 500 MHz): d = 9.54 (s, 1H), 7.57 (d,
J = 7.9 Hz, 2H), 7.49 (s, 1H), 7.33–7.36 (m, 4H), 7.31 (d,
J = 7.9 Hz, 2H), 7.27 (t, b, 1H), 7.18 (d, J = 7.9 Hz, 1H),
7.08–7.12 (m, 2H), 3.93 (d, J = 13.0 Hz, 1H), 3.83 (d,
J = 12.7 Hz, 1H), 3.77 (dd, J1,2 = 3.8 Hz, J1,3 = 7.5,
1H), 3.50 (dd, J1,2 = 3.4 Hz, J1,3 = 17.5 Hz, 1H), 3.34
(dd, J1,2 = 7.5 Hz, J1,3 = 17.5 Hz, 1H), 2.45 (s, 3H), 2.34
(s, 3H) ppm; 13C NMR (CDCl3, 125 MHz): d = 202.4,
171.6, 139.3, 137.7, 136.7, 135.4, 132.7, 132.0, 129.6,
129.0, 128.7, 128.1, 127.5, 124.1, 119.3, 59.1, 52.5, 42.4,
21.1, 20.8 ppm; HR/MS: calc for C25H26N2O2 (M ? H?)
387.20670, found 387.20584.
2.5 9 10-5 mol of 1–10 were dissolved in methanol in
volumetric flask of 10.00 cm3 to obtain stock solutions.
Around 1 9 10-5 mol of 11–13 were used because of limited
solubility of compounds in MeOH. Aliquots (*2 9 10-7
mol) of stock solutions of 1–13 were added in a quartz
cuvette with the automatic pipette, and then 20-fold molar
excess of deprotonated amine (C5H10N:- or BzNH:-) in
methanol (c = 0.02 M) was added. Deprotonated amines
were prepared by the addition of stoichiometric equivalent of
strong base, KOH, dissolved in MeOH. Pseudo first order
rate constants (k0) were calculated by linearization of time
scan plots, Eq. (2):
ꢀ
ꢁ
At ꢂ A0
ln
¼ ꢂk0 ꢀ t;
ð2Þ
A0 ꢂ A1
where At is an absorbance of the solution in the time t, A?
is the absorbance after completing of the reaction, and A0 is
the initial absorbance. The k0 was obtained as a mean from
six independent measurements, using the same molar
excess of amines. Second order rate constants were
obtained by dividing k0 with an amine/investigated com-
pound molar ratio.
Modeling
The values of Hammett substituent constants used in cor-
relations were adopted from the literature [19, 20].
Cumulative substituent constants were used for compounds
5 and 13. Nucleophilicity parameters N for piperidine and
benzylamine are adopted from H. Mayr’s ‘Database of
Nucleophilicities and Electrophilicities’ [21]; using the
data experimentally obtained in CH3OH/CH3CN (91/9)
mixture [14], with the experimental setup closest to the
experimental conditions used in this work. Initial geome-
tries of compounds 1–13, 1a, and 6a were obtained from
SMILES notation in OMEGA [22, 23], as global minima
with MMFF94s force field. The full geometry optimization
was done in the Gaussian03 program [24] on the MP2 level
of theory, using the 6-311G basis set, and tight criteria for
self-consistent field convergence (SCF = tight keyword).
The optimization of the (intermediate) geometries of
compounds 1a and 6a on a semiempirical level of theory
was done by the PM6 method [25] in MOPAC2012 [26,
27], using the implicit solvent model (COSMO). The UV/
Vis spectra of compound 1, 6, 1a, and 6a were calculated
from geometries found as the global minima on MP2 level
of theory, by the semiempirical ZINDO/S method [28],
using the implicit solvent model (polarizable continuum
model, PCM—methanol). Time-dependent density func-
tional (B3LYP/6-311g) and ZINDO/S calculations were
performed in Gaussian09. All molecular orbitals are
Acknowledgments The Ministry of Education, Science and Tech-
nological Development of Serbia support this work under Grant
172035. Authors gratefully acknowledge OpenEye Scientific Soft-
ware, Santa Fe, NM, for the free academic licensing of software tools.
The work reported makes use of results produced by the High-Per-
formance Computing Infrastructure for South East Europe’s Research
Communities (HP-SEE), a project co-funded by the European Com-
mission (under Contract Number 261499) through the Seventh
gratefully acknowledge computational time provided on the PARA-
DOX cluster at the Scientific Computing Laboratory of the Institute of
Physics Belgrade (SCL-IPB), supported in part by the Serbian Min-
istry of Education, Science and Technological Development under
projects No. ON171017 and III43007, and by the European Com-
mission under FP7 projects PRACE-3IP and EGI-InSPIRE.
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