13C NMR spectra of 4-hydroxymethylpyrazoles and their chemical behavior at heating

Article abstract of DOI:10.1134/S1070363210050245

It was established that in the¹³C NMR spectra of 4-hydroxymethylpyrazoles the carbon atom of hydroxymethyl group of 1,3,5-trimethyl-4-hydroxymethylpyrazole is deshielded by 6.28-6.78 ppm compared to 1-methyl-4-hydroxymethyl-, 1,3-dimethyl-4-hydroxymethyl-and 1,5-dimethyl-4-hydroxymethylpyrazoles. It is assumed that this difference is related to their dissimilar behavior at heating. Pleiades Publishing, Ltd., 2010.

Full text of DOI:10.1134/S1070363210050245

ISSN 1070-3632, Russian Journal of General Chemistry, 2010, Vol. 80, No. 5, pp. 1001–1003. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © A.O. Baltayan, V.I. Rstakyan, S.K. Antanosyan, D.A. Tadevosyan, O.S. Attaryan, G.V. Asratyan, 2010, published in Zhurnal
Obshchei Khimii, 2010, Vol. 80, No. 5, pp. 831–833.
13C NMR Spectra of 4-Hydroxymethylpyrazoles
and Their Chemical Behavior at Heating
A. O. Baltayana, V. I. Rstakyana, S. K. Antanosyana,
D. A. Tadevosyana, O. S. Attaryanb, and G. V. Asratyanb
a Institute of Organic Chemistry, the National Academy of Sciences of Republic of Armenia,
ul. Zakaria Sarkavaga 167a, Yerevan, 375091 Armenia
e-mail: angelabaltayan@mail.ru
b Institute of Applied Chemistry “ARIAK” of Republic of Armenia, Yerevan, Armenia
Received August 4, 2009
Abstract―It was established that in the 13C NMR spectra of 4-hydroxymethylpyrazoles the carbon atom of
hydroxymethyl group of 1,3,5-trimethyl-4-hydroxymethylpyrazole is deshielded by 6.28–6.78 ppm compared
to 1-methyl-4-hydroxymethyl-, 1,3-dimethyl-4-hydroxymethyl- and 1,5-dimethyl-4-hydroxymethylpyrazoles.
It is assumed that this difference is related to their dissimilar behavior at heating.
DOI: 10.1134/S1070363210050245
It was found that distillation of 1,3,5-trimethyl-4-
hydroxymethylpyrazole IV led to the formation of the
corresponding symmetrical ether V in ~90 % yield [1].
1-methyl-4-hydroxymethylpyrazole I, 1,3-dimethyl-4-
hydroxymethylpyrazole II, and 1,5-dimethyl-4-hyd-
roxymethylpyrazole III.
In order to ascertain the general nature of the
detected cross-coupling of 4-hydroxymethylpyrazoles
I–III, in this study we have carried out the synthesis of
The study showed that in contrast to 1,3,5-tri-
methyl-4-hydroxymethylpyrazole IV compounds I–III
did not enter the cross-coupling reaction at distillation.
R
R
O
R
IV
HO
R'
N
N
N
R' R'
N
N
I_III
N
Me
Me
Me
V
I_IV
I: R = R' = H; II: R = CH3, R' = H; III: R = H, R' = CH3; IV–V: R = R' = CH3.
13
The comparison of the 13C NMR spectral data listed
in the table shows that in the compound IV the total
electron density on the ring carbon atoms is reduced
compared to compounds I–III, and chemical shifts in
13C NMR spectra in total increase, the difference is
7.28 ppm compared to I, 2.38 ppm compared to II and
3.54 ppm compared to III. This is due to the fact that
in going from compound I to IV the electron density
on the nitrogen atoms increases because of the
influence of donor methyl groups. This is in agreement
with the available literature data on the increase of the
relative basicity of N-vinylpyrroles at the introduction
into the ring of alkyl substituents [2]. A change in C
NMR chemical shifts of 160–200 ppm corresponds to
the full transition of one π-electron [3, 4].
Interestingly, in compound IV the carbon atom of
hydroxymethyl group “feels” the increase in the
electron density on the nitrogen atom and suffers a
shift of its signal downfield by 6.28–6.70 ppm
compared to compounds I–III.
This unexpected demonstration of the effect of
“long-range” action most likely is due to the inter-
action of π-electronic systems through the nitrogen
1001

1002
BALTAYAN et al.
Parameters of 13C NMR spectra of 4-hydroxymethylpyrazoles I–IV
Chemical shifts, δ, ppm
Compounds I–IV
С1
С2
С3
ΣС
ΔΣС
С*
ΔС*
132.27
121.95
127.28
385.50
7.28
54.36
6.28
*HO
N
N
Me
Me
145.51
118.63
127.26
391.40
2.38
54.29
6.35
*HO
N
N
Me
*HO
Me
137.32
145.28
118.02
112.35
134.90
136.15
390.24
393.78
3.54
53.94
60.64
6.7
N
N
Me
Me
–
–
*HO
Me
N
N
Me
heteroatoms of the molecules of compound IV.
Deshielding of the carbon nucleus of hydroxymethyl
group in compound IV is likely to cause its different
behavior at the distillation as compared to compounds
I–III.
at cooling with ice water for 1 h, then at room
temperature for 3 h. The solution was acidified with
hydrochloric acid, the reaction mixture was neutralized
with potassium carbonate, extracted with chloroform,
and the extract was dried over magnesium sulfate.
After distilling the solvent off, the residue was distilled
in a vacuum.
EXPERIMENTAL
Yield 81 %, bp 92–94°C (1 mm Hg), nD20 1.5122,
IR spectra were taken on a Specord 75-UR
d420 1.0591. IR spectrum, ν, cm–1: 1520 (heterocycle,
1
instrument (thin layer), the H and 13C NMR spectra
1
ring), 3200–3400 (OH). H NMR spectrum (DMSO-
were recorded on a Varian Mercury device (300 MHz)
from solutions in DMSO-d6.
d6), δ, ppm, J (Hz): 3.80 s (3H, N–CH3), 3.92 br.t (1H,
OH, J 3.4), 4.20 br.d (2H, CH2, J 3.4), 7.74 s (1H, 3-
H), 8.10 s (1H, 5-H). Found, %: C 53.28, H 6.84; N
25.57. C8H5N2O. Calculated, %: C 53.57, H 7.14; N
25.00.
The original 4-formylpyrazoles are synthesized by
known methods described in [5, 6], 1-methyl-4-for-
mylpyrazole, bp 80–81°C (1 mm Hg), 1,3-Dimethyl-4-
formylpyrazole, mp 50°C, 1,5-dimethyl-4-formyl-
pyrazole, mp 60°C.
1,3-Dimethyl-4-hydroxymethylpyrazole
(II).
Similarly, from 0.1 mol of 1,3-dimethyl-4-formyl-
pyrazole in 82% yield was prepared compound II, bp
107–109°C (1 mm Hg), nD20 1.5135, d420 1.0691. IR
spectrum, ν, cm–1: 1530 (heterocycle, ring), 3200–3400
1-Methyl-4-hydroxymethylpyrazole (I). To a cold
solution of 0.1 mol of 1-methyl-4-formylpyrazole,
1.2 g of triethylbenzylammonium chloride in 50 ml of
water over 1 h was added by portions 0.1 mol of
sodium borohydride maintaining the temperature of the
reaction mixture below 10°C. The mixture was stirred
1
(OH). H NMR spectrum (DMSO-d6), δ, ppm, J (Hz):
2.15 s (3H, 3-CH3), 3.31 s (3H, N–CH3), 3.84 br.t (1H,
OH, J 3.5), 4.25 br.d (2H, CH2, J 3.4), 8.15 s (1H,
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 5 2010

13C NMR SPECTRA OF 4-HYDROXYMETHYLPYRAZOLES
5-H). Found, %: C 56.72, H 7.24; N 22.57. C6H10N2O.
REFERENCES
1003
Calculated, %: C 57.14, H 7.94; N 22.22.
1. Attaryan, O.S., Gevorgyan, A.A., Antanosyan, S.K.,
Martirosyan, S.S,, Panosyan, G.A., and Matsoyan, S.G.,
Zh. Obshch. Khim., 2005, vol. 75, no. 9, p. 1575.
1,5-Dimethyl-4-hydroxymethylpyrazole
(III).
Prepared like preceding compound from 0.1 mol of
1,5-dimethyl-4-formylpyrazole in 85% yield, bp 115–
117°C (1 mm Hg), mp 81–82°C. IR spectrum, ν, cm–1:
2. Trofimov, B.A., Golovanova, N.I., Mikhaleva, A.I.,
Korostova, S.E., Balabanova, L.N., and Vasil’ev, A.N.,
Khim. Geterotsikl. Soedin., 1977, no. 7, p. 915.
3. Lauterbur, P.S., J. Am. Chem. Soc., 1961, vol. 83, p. 1838.
4. Spiesecke, H. and Shnider, W.G., Tetrahedron. Lett.,
1
1530 (heterocycle, ring), 3200–3400 (OH). H NMR
spectrum (DMSO-d6), δ, ppm, J (Hz): 2.21 s (3H, 5-
CH3), 3.95 s (3H, N–CH3), 3.85 br.t (1H, OH, J 3.5),
4.25 br.d (2H, CH2, J 3.4), 7.62 s (1H, 3-H). Found, %:
C 57.68, H 7.38; N 22.61. C6H10N2O. Calculated, %: C
57.14, H 7.94; N 22.22.
1961, no. 5, p. 468.
5. Finar, I.L. and Lord, G.H., J. Chem. Soc., 1957, no. 7,
p. 3314.
6. Antanosyan, S.K., Khim. Zh. Armenia, 2006, vol. 59,
no. 2, p. 99.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 5 2010