Reactions of N-Allyl- and N-Propargyltriflimides with N,N′-Disubstituted Carbodiimides

Article abstract of DOI:10.1134/S1070428018070229

The alkylating activity of N-allyl- and N-propargyltriflimides toward N,N′-dicyclohexyl- and N,N′-diphenylcarbodiimides has been studied. Activation of the nitrogen atom by two electron-withdrawing trifluoromethanesulfonyl groups favors cleavage of the C–N bond in the absence of a catalyst with the formation of N-substituted unsaturated ureas.

Full text of DOI:10.1134/S1070428018070229

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2018, Vol. 54, No. 7, pp. 1103–1105. © Pleiades Publishing, Ltd., 2018.
Original Russian Text © L.L. Tolstikova, Yu.S. Danilevich, B.A. Shainyan, 2018, published in Zhurnal Organicheskoi Khimii, 2018, Vol. 54, No. 7,
pp. 1095–1097.
SHORT
COMMUNICATIONS
Reactions of N-Allyl- and N-Propargyltriflimides
with N,N′-Disubstituted Carbodiimides
L. L. Tolstikovaa, Yu. S. Danilevicha, and B. A. Shainyana*
a Favorskii Irkutsk Institute of Chemistry, Siberian Branch, Russian Academy of Sciences,
ul. Favorskogo 1, Irkutsk, 664033 Russia
*e-mail: bagrat@irioch.irk.ru
Received February 21, 2018
Abstract—The alkylating activity of N-allyl- and N-propargyltriflimides toward N,N′-dicyclohexyl- and
N,N′-diphenylcarbodiimides has been studied. Activation of the nitrogen atom by two electron-withdrawing
trifluoromethanesulfonyl groups favors cleavage of the C–N bond in the absence of a catalyst with the forma-
tion of N-substituted unsaturated ureas.
DOI: 10.1134/S1070428018070229
Unsaturated triflimide derivatives of the general
formula Tf2NR (Tf = CF3SO2, R = CH=CHR′,
CH2CH=CH2, CH2C≡CH) are interesting compounds
from the viewpoints of both their synthetic potential
and probable tautomeric transformations. Their mole-
cules contain two strong electron-withdrawing tri-
fluoromethanesulfonyl groups on the nitrogen atom,
which could considerably extend synthetic potential
of unsaturated triflimide derivatives. Prior to our
studies in this field [1], only N-vinyltriflimides
(Tf2NCH=CHAlk) [2] and N-allyltriflimide
(Tf2NCH2CH=CH2) [3, 4] have been described.
N-Vinyltriflimides were formed as minor products in
the reactions of triflimide potassium salt with (E)-1-al-
kenyl-(4-trifluoromethylphenyl)-λ3-bromanes, the
major products being the corresponding O-vinyl
isomers TfN=S(O)(CF3)OCH=CHAlk [2]. Crude
N-allyltriflimide was isolated as a brown oily material
in the reaction of allylamine with trifluoromethanesul-
fonic anhydride [3, 4]; the pure compound obtained
after distillation was a colorless liquid [1].
conversion by carrying out the reaction in a solvent
(methylene chloride or chloroform), adding Y(OTf)3 as
catalyst, or heating to 50–60°C. NMR analysis of the
reaction mixture showed the presence of three com-
pounds. N,N′,N″-Tricyclohexylguanidinium bis(tri-
fluoromethanesulfonyl)imide (5) was identified by the
signal at δF –78.54 ppm in the 19F NMR spectrum of
the product mixture, which coincided with that of
a sample of 5 prepared by us previously [6]. By
column chromatography we also isolated N,N′-dicyclo-
hexyl-N-propargylurea 6 and N,N′-(1,3-dicyclohexyl-
1,3-diazetidine-2,4-diylidene)dimethanamine 8; the
ratio 5:6:8 was 3:1:5 (Scheme 1). Compound 8 is
a dimer of 3 which is likely to be formed under cata-
lysis by triflimide present in the reaction mixture, by
analogy with the dimerization of 3 catalyzed by tetra-
fluoroboric acid [7, 8].
The NMR spectral data and melting point of 8 coin-
cided with those reported for N,N′-dicyclohexylcarbo-
diimide dimer obtained by treatment of the solid
Scheme 1.
In continuation of our studies on unsaturated
triflimide derivatives [1, 5], herein we report the
reactions of N-propargyl- and N-allyltriflimides 1 and
2 with N,N′-dicyclohexyl- and N,N′-diphenylcarbodi-
imides 3 and 4.
Tf2NR
+
CyN
Cy
C
NCy
(CyNH)3C –NTf2
1, 2
3
5
Cy
N
Cy
NCy
H
N
N
+
+
R
N
In the reaction of pure compounds 1 and 3 at a ratio
of 1:1 at room temperature, the conversion was 20%
after 5 days; the conversion increased to 55% when
2 equiv of 3 was used. We failed to increase the
CyN
Cy
O
6, 7
8
1, 6, R = CH≡CCH2; 2, 7, CH2=CHCH2.
1103

TOLSTIKOVA et al.
1104
Scheme 2.
monomer with SO2 [9], as well as for the minor prod-
uct in the peptide synthesis with 1-hydroxybenzo-
triazole [10] or by-product in the esterification with
carbodiimide 3 as dehydrating agent [11].
Tf2NR
+
CyN
C
NCy
1, 2
3
Cy
H2O
The reaction of N-allyltriflimide 2 with carbodi-
imide 3 at a ratio of 1:2 at room temperature was
characterized by a conversion of higher than 95%, and
the products were N-allyl-N,N′-dicyclohexylurea 7 and
compounds 5 and 8 at a ratio of 1:1:1.
6, 7
CyN
C
N
NTf2
–Tf2NH
R
9, 10
Tf2NH
CyN
C
NCy
5
+ 8
The structure of the products was proved by IR and
1H, 13C, and 19F NMR spectra and elemental analyses.
The IR spectra of ureas 6 and 7 contained a carbonyl
stretching band at 1626 and 1622 cm–1, respectively,
which almost coincided with the νC=O band of N,N′-di-
cyclohexylurea (1626 cm–1). The IR spectrum of 6 also
contained νC≡C (2111 cm–1) and νC–H bands (3309 cm–1)
typical of terminal alkynes. The asymmetric structure
of 6 and 7 followed from the presence in their
1H NMR spectra of two NCH signals belonging to two
nonequivalent cyclohexyl groups; these signals ap-
peared ~0.5 and 0.7 ppm downfield relative to the
corresponding signal of initial carbodiimide 3. In the
spectrum of 6, the CH2 and ≡CH signals were located
in a stronger field (Δδ = ~0.8 and 0.3 ppm, respec-
tively) relative to those of N-propargyltriflimide. The
direction of the double bond polarization in 7 was the
same as in 2. The allyl protons in 7 resonated in
a stronger field (by ~0.95, 0.15, and 0.2 ppm for CH2,
CH=, and =CH2, respectively) relative to the corre-
sponding protons of N-allyltriflimide. In the 13C NMR
spectrum of 6, signals of carbon atoms of the propargyl
group were located at δC 34, 72, and 81 ppm, and the
allyl carbon nuclei in 7 gave rise to signals at δC 49,
116, and 136 ppm. The carbonyl carbon nucleus of
both compounds 6 and 7 resonated at δC 157 ppm.
Our results suggest a reaction mechanism involving
nucleophilic substitution of nucleofugal triflimide
residue in molecule 1 or 2 by the action of N,N′-di-
cyclohexylcarbodiimide with intermediate formation
of salt 9 or 10. Hydrolysis of the latter in the presence
of atmospheric moisture yields N-substituted N,N′-di-
cyclohexylurea 6 or 7 and triflimide molecule. Nucleo-
philic substitution in triflimides with saturated substit-
uents on the nitrogen atom has been reported [12–15].
Triflimide reacts with N,N′-dicyclohexylcarbodiimide
according to the mechanism proposed in [6] to give
salt 5 and, by analogy with [7, 8], catalyzes di-
merization of N,N′-dicyclohexylcarbodiimide with the
formation of compound 8 (Scheme 2).
1, 6, 9, R = CH≡CCH2; 2, 7, 10, CH2=CHCH2.
ditions. Compound 1 failed to react with N,N′-di-
phenylcarbodiimide (4). The low reactivity of N,N′-di-
arylcarbodiimides compared to their N,N′-dialkyl
analogs was noted in some publications; in particular,
this was observed in the reactions with triflamide
leading to guanidines, catalyzed by CuCl and under
mechanical activation (liquid-assisted grinding) [16].
The alkylation of N,N′-diphenylcarbodiimide (4) with
N-allyltriflimide (2) follows Scheme 1; however, we
failed to isolate analytically pure N-allyl-N,N′-di-
phenylurea (11), and it was characterized only by
1H NMR. Compound 11 underwent hydrolysis to
N,N′-diphenylurea and allyl alcohol during attempted
isolation by column chromatography. No diphenylcar-
bodiimide dimer was formed in this reaction.
Thus, the reaction of N-allyl- and N-propargyl-
triflimides with N,N′-dicyclohexyl- and N,N′-diphenyl-
carbodiimides provides a new method of synthesis of
unsaturated N-substituted ureas which can be subjected
to further modification through the multiple bonds.
Reactions of N,N′-dicyclohexylcarbodiimide
with N-propargyl- and N-allyltriflimides (general
procedure). A mixture of N,N′-dicyclohexylcarbodi-
imide and compound 1 or 2 at a ratio of 2 :1 was
stirred for 5 days at room temperature. Unreacted
N-substituted triflimide was removed under reduced
pressure (0.2 mm) at 40°C, and the residue (~0.5 g)
was dissolved in a small amount of chloroform.
Compound 8 and N-substituted urea 6 or 7 were
isolated by column chromatography on silica gel
(0.125–0.200 mm) using hexane–ethyl acetate (4:1 for
6 or 5:3 for 7) as eluent.
N,N′-(1,3-Dicyclohexyl-1,3-diazetidine-2,4-di-
ylidene)dimethanamine (8). Yield ~10%, colorless
crystals, mp 115–120°C; published data [9]: mp 115–
118°C.
Unsaturated triflimide derivatives 1 and 2 did not
react with N,N′-dicyclohexylurea under analogous con-
N,N′-Dicyclohexyl-N-(prop-2-yn-1-yl)urea (6).
Yield 55%, white crystals, mp 93°C. IR spectrum
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 54 No. 7 2018

REACTIONS OF N-ALLYL- AND N-PROPARGYLTRIFLIMIDES
1105
(film), ν, cm–1: 3309 (C≡CH), 3221, 2929, 2855, 2111
(C≡C), 1626, 1529, 1451, 1236. 1H NMR spectrum, δ,
ppm: 1.10–1.21 m (4H, CH2), 1.36 t (6H, CH2, J =
10.1 Hz), 1.63 s (2H, CH2), 1.67–1.71 m (2H, CH2),
1.78–1.80 m (4H, CH2), 1.93–1.96 m (2H, CH2), 2.26 t
(1H, CH, J = 2.4 Hz), 3.67–3.71 m (1H, NCH), 3.86 d
(2H, CH2, J = 2.2 Hz), 4.00–4.05 m (1H, NCH), 4.53 d
(1H, NH, J = 6.1 Hz). 13C NMR spectrum, δC, ppm:
24.83, 25.54, 25.69, 25.84, 31.08, 31.24, 33.74, 49.36,
54.27, 71.81 (≡CH), 80.92 (C≡), 156.85 (C=O).
Found, %: C 72.99; H 10.04; N 10.46. C16H26N2O.
Calculated, %: C 73.24; H 9.99; N 10.68.
The IR spectra were recorded on a Bruker Vertex
70 spectrometer. The NMR spectra were measured on
a Bruker DPX-400 instrument at 400 (1H), 100 (13C),
and 376 MHz (19F) using CDCl3 as solvent and
reference; the chemical shifts are given relative to
tetramethylsilane (1H, 13C) or CCl3F (19F). The prog-
ress of reactions was monitored by TLC on Silufol
UV-254 plates.
This study was performed under financial support
by the Russian Foundation for Basic Research (project
no. 17-03-00213) using the equipment of the Baikal
Joint Analytical Center (Siberian Branch, Russian
Academy of Sciences).
N,N′-Dicyclohexyl-N-(prop-2-en-1-yl)urea (7).
Yield 65%, white crystals, mp 69–70°C. IR spectrum
(film), ν, cm–1: 3349, 2928, 2854, 1622, 1527, 1233.
1H NMR spectrum, δ, ppm: 1.02–1.37 m (10H, CH2),
1.54–1.65 m (4H, CH2), 1.73 t (4H, CH2, J = 14.5 Hz),
1.86–1.90 m (2H, CH2), 3.61–3.64 m (1H, NCH),
3.68 d.d (2H, CH2, J = 4.5, 1.8 Hz), 4.17 t.t (1H, NCH,
J = 11.8, 3.4 Hz), 4.29 d (1H, NH, J = 6.7 Hz),
5.19 d.d (1H, =CH2, J = 10.4, 1.04 Hz), 5.24 d.d (1H,
=CH2, J = 17.5, 0.9 Hz), 5.79 d.d.t (1H, CH=, J = 11.9,
10.4, 5.3 Hz). 13C NMR spectrum, δC, ppm: 24.81,
25.63, 25.72, 25.88, 31.13, 33.76, 44.79, 49.07, 53.66,
116.08, 136.54, 157.58 (C=O). Found, %: C 72.26;
H 10.67; N 10.30. C16H28N2O. Calculated, %: C 72.68;
H 10.67; N 10.59.
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