Kinetic and equilibrium parameters of [4+2] cycloaddition reaction of 2,6-dimethylnaphthalene with 4-phenyl-1,2,4-triazoline-3,5-dione

Article abstract of DOI:10.1007/s11172-014-0506-x

Kinetic parameters of forward and retro Diels-Alder reactions between 2,6-dimethylnaphthalene and 4-phenyl-1,2,4-triazolinedione were determined, as well as the equilibrium parameters of the reaction in 1,2-dichloroethane.

Full text of DOI:10.1007/s11172-014-0506-x

Russian Chemical Bulletin, International Edition, Vol. 63, No. 3, pp. 770—771, March, 2014
770
Kinetic and equilibrium parameters of [4+2] cycloaddition reaction
of 2,6ꢀdimethylnaphthalene with 4ꢀphenylꢀ1,2,4ꢀtriazolineꢀ3,5ꢀdione
V. D. Kiselev,a E. A. Kashaeva,a L. N. Potapova,a D. A. Kornilov,a and A. I. Konovalovb
aA. M. Butlerov Chemical Institute of Kazan Federal University,
18 ul. Kremlevskaya, 420008 Kazan, Russian Federation.
Fax: +7 (843) 292 7278. Eꢀmail: vkiselev.ksu@gmail.com
bA. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center of the Russian Academy of Sciences,
8 ul. Akad. Arbuzova, 420088 Kazan, Russian Federation.
Fax: +7 (843) 273 1872
Kinetic parameters of forward and retro Diels—Alder reactions between 2,6ꢀdimethylꢀ
naphthalene and 4ꢀphenylꢀ1,2,4ꢀtriazolinedione were determined, as well as the equilibrium
parameters of the reaction in 1,2ꢀdichloroethane.
Key words: 2,6ꢀdimethylnaphthalene, 4ꢀphenylꢀ1,2,4ꢀtriazolinedione, Diels—Alder reacꢀ
tion, reaction rate, equilibrium.
Scheme 1
In the sequence of aromatic dienes: benzene, naphthaꢀ
lene, anthracene, only the latter can be relatively easily
involved in the Diels—Alder reaction with dienophiles.1
Benzene fails to give this reaction due to the extremely
unfavorable kinetic and equilibrium parameters. The reꢀ
action adduct between Nꢀphenylmaleimide and naphthꢀ
alene was obtained earlier by gallium chloride catalysis,2
as well as under high pressure, which allowed to use eleꢀ
vated temperature.2,3 The N=N bond in 4ꢀphenylꢀ1,2,4ꢀ
triazolineꢀ3,5ꢀdione is more active by almost five orders of
magnitude in the Diels—Alder reaction than the C=C
bond in the structural analog, Nꢀphenylmaleimide, that
allows one to obtain data on kinetic and equilibrium paꢀ
rameters of the Diels—Alder reaction even with low active
dienes.4 We have obtained kinetic and equilibrium paramꢀ
eters for the Diels—Alder reaction between 4ꢀphenylꢀ
1,2,4ꢀtriazolineꢀ3,5ꢀdione (1) and 2,6ꢀdimethylnaphthaꢀ
lene (2) in 1,2ꢀdichloroethane (Scheme 1). Recently, it
was shown5 that the active 9,10ꢀreaction center in 9,10ꢀdiꢀ
phenylanthracene 4 is completely blocked because of
orthogonality of the anthracene plane and the plane of
phenyl groups, that excludes a possibility of reaction with
all known dienophiles with the C=Cꢀreaction center.
Dienophile 1 was found to react with diene 4 at the
sterically available 1,4ꢀatoms of this diene.5 It was interꢀ
esting to compare kinetic and equilibrium parameters of
the cycloaddition reactions of 4ꢀphenylꢀ1,2,4ꢀtriazolineꢀ
3,5ꢀdione at atoms C(1) and C(4) of dienes 2 and 4.
The equilibrium constants obtained for the reaction
–44.0 2 kJ mol–1 and –130 6 J mol–1 K–1, respectively.
The rate constants of the forward reaction 1 + 2
equal to 3.26•10–4, 4.41•10–4, and 8.25•10–4 L mol–1 s–1
at 20.0, 25.0, and 35.0 C, respectively. From these data,
the activation enthalpy (44.2 4 kJ mol–1) and entropy
(–161 13 J mol–1 K–1) were calculated. The rate conꢀ

3 are
3 are equal to 11.15, 8.40, and 4.48 L mol–1

1 + 2

at 20.0, 25.0, and 35.0 C, respectively. The calculꢀ

ated enthalpy and entropy values of the reaction are
stants of the adduct 3 decomposition (3 1 + 2), calcuꢀ
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 0770—0771, March, 2014.
1066ꢀ5285/14/6303ꢀ0770 © 2014 Springer Science+Business Media, Inc.

2,6ꢀDimethylnaphtalene in the Diels—Alder reaction Russ.Chem.Bull., Int.Ed., Vol. 63, No. 3, March, 2014
771
The data completely agree with the structure of adduct 3 and are
close to the data for the adduct of the reaction of 2 with
4ꢀmethyltriazolinedione.6
lated from the relation of the rate constants of the forward

reaction 1 + 2
3 and the equilibrium constants, are
equal to 2.92•10–5, 5.07•10–5, and 17.6•10–5 s–1 at 20.0,
Solvents were dried using standard procedures.7 Since reꢀ
agent 1 is sensitive to moisture, the constancy of optical density
of solutions in time was controlled before kinetic measurements.
Kinetic measurements were carried out under pseudo first order
conditions on a HITACHI Uꢀ2900 spectrophotometer. Initial
25.0, and 35.0 C, respectively. The activation enthalpy
–1

and entropy of the process 3 1 + 2 are 88.2 4 kJ mol
and –31 13 J mol–1 K–1, respectively.

For the reaction 1 + 4 5, where addition takes place
concentrations of reagents: C2 = 0.17—0.21 mol L–1, C1
=
at atoms C(1) and C(4) of diene 4, the following rate
constants in toluene were obtained: 2.72•10–3; 5.73•10–3
,
= (5.9—7.2)•10–3 mol L–1. The constancy of residual absorpꢀ
tion of 1 with time was a criterion of a steadyꢀstate equilibrium.
The equilibrium was set up within 25 h. The course of the forꢀ
ward reaction was monitored based on the decrease in the abꢀ
and 12.5•10–3 L mol–1 s–1 at 25, 35, and 45 C, respecꢀ
tively. The rate constants of decomposition of adduct
–6

5
1 + 4 for these temperatures are equal to 1.29•10 ,
sorption of 1 in 1,2ꢀdichloroethane, 
= 540 nm ( 178),
5.12•10–6, and 23.4•10–6 s–1, respectively. The calculatꢀ
ed enthalpy and entropy of activation for the reaction
max
where compounds 2 and 3 are transparent. Kinetic measureꢀ

ments for the reaction 1 + 4
5 in toluene were carried out
1 + 4 5 are equal to 58.6 kJ mol–1 and –97 J mol–1 K–1
,


similarly. The rate of the retro reaction 5
1 + 4 was studied
whereas for the reaction 5 1 + 4 to 108.8 kJ mol–1 and
7 J mol–1 K–1. From this it follows that the enthalpy
(–50.2 kJ mol–1) and the entropy (–104 J mol–1 K–1) for

under conditions excluding equilibrium. For this, decomposiꢀ
tion of adduct 5 was carried out in the presence of trans,transꢀ
1,4ꢀdiphenylbutaꢀ1,3ꢀdiene, which rapidly and irreversibly
caught dienophile 1 formed upon decomposition of adduct 5.
The reaction rate was monitored based on the increase in the
absorption of diene 4 on the 395 nm wavelength.

the reaction 1 + 4
5 are close to the corresponding

parameters for the reaction 1 + 2 3.
Earlier, it has been shown4 that the enthalpy in the
Diels—Alder reaction with dienophile 1 and 4ꢀphenylꢀ
maleimide is virtually the same. The enthalpy of the reꢀ
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 12ꢀ03ꢀ
00029a).

action 1 + 2
3 determined in the present work
(–44.0 kJ mol–1) is close to the value calculated earlier1
(–43 4 kJ mol–1) based on the heat of 1,4ꢀdihydrogenaꢀ
tion of the diene.
References
In conclusion, extremely high activity of 4ꢀphenylꢀ
1,2,4ꢀtriazolineꢀ3,5ꢀdione allowed us to determine kinetꢀ
ic and thermodynamic parameters in the Diels—Alder reꢀ
action with strongly conjugated and low active diene, viz.,
2,6ꢀdimethylnaphthalene.
1. V. D. Kiselev, I. I. Shakirova, A. I. Konovalov, Russ. Chem.
Bull. (Int. Ed.), 2013, 62, 285 [Izv. Acad. Nauk, Ser. Khim.,
2013, 290].
2. G. G. Iskhakova, V. D. Kiselev, E. A. Kashaeva, L. N. Poꢀ
tapova, E. A. Berdnikov, D. B. Krivolapov, I. A. Litvinov,
ARKIVOC, 2004, 12, 70.
3. F.ꢀG. Klärner, V. Breitkopf, Eur. J. Org. Chem., 1999, 11, 2757.
4. V. D. Kiselev, I. I. Shakirova, D. A. Kornilov, H. A. Kashaeꢀ
va, L. N. Potapova, A. I. Konovalov, J. Phys. Org. Chem.,
2013, 26, 47.
5. V. D. Kiselev, I. I. Shakirova, H. A. Kashaeva, L. N. Potapoꢀ
va, D. A. Kornilov, D. B. Krivolapov, A. I. Konovalov, Menꢀ
deleev Commun., 2013, 23, 235.
6. G. W. Breton, K. A. Newton, J. Org. Chem., 2000, 65, 2863.
7. J. A. Riddick, W. B. Bunger, T. K. Sakano, Organic Solvents,
New York—Chichester—Brisbane—Toronto—Singapore,
John Wiley, 1986, 4th ed.
Experimental
Dienophile 1 (Aldrich, 97%) was sublimed at 100 oC and 10 Pa;
m.p. 180 C (decomp.), max(benzene) = 540 nm ( 248),
max(dioxane) = 527 nm ( 186). Dienes 2 and 4 (Aldrich, 99%)
were used without additional purification. Product 5 was obꢀ
tained according to the procedure described earlier.5 Physicoꢀ
chemical and spectral characteristics agreed with those given
in work.5
(1R,8S)ꢀ4,15ꢀDimethylꢀ11ꢀphenylꢀ9,11,13ꢀtriazatetracycloꢀ
[6.5.2.02,7.09,13]pentadecaꢀ2,4,6,14ꢀtetraeneꢀ10,12ꢀdione (3).
1H NMR (400 MHz, CDCl3), 25 C,  : 7.20—7.60, 6.29

H
(d.quint, 1 H, J = 5.8 Hz, J = 1.8 Hz); 5.67 (d, 1 H, J = 5.8 Hz);
5.50 (d, 1 H, J = 1.8 Hz); 2.21 (s, 3 H); 1.89 (d, 3 H, J = 1.9 Hz).
Received December 17, 2013;
in revised form March 13, 2014