Triacylperhydro-1,3,5-triazines over phenylsulfonic acid functionalized mesoporous silica

Article abstract of DOI:10.1080/00397911.2010.517887

An operationally simple, efficient, and environmentally benign synthesis of 1,3,5-triacylperhydro-1,3,5-triazines in good yields by reaction of different organic nitriles and trioxane in the presence of phenylsulfonic acid functionalized mesoporous silica under mild conditions was examined. The yields of the corresponding 1,3,5-trisubstituted perhydro-s-triazines synthesized from acetonitrile, propionitrile, butyronitrile, benzonitrile, and 1.3.5-trioxane were 95.7%, 96.1%, 84.2%, and 98.1%, respectively. The products were characterized by 1H NMR, infrared, mass spectrometry, and elemental analysis. The mechanism of the formation of 1,3,5-triacylperhydro-1,3,5-triazines in acidic conditions was also described using a model reaction of butyronitrile with trioxane.

Full text of DOI:10.1080/00397911.2010.517887

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Triacylperhydro-1,3,5-triazines over
Phenylsulfonic Acid Functionalized
Mesoporous Silica
a
a
a
a
Jianming Yang , Qinwei Yu , Fengwei Zhao , Jian Lu
&
a
Zhongxue Ge
a
Xi'an Modern Chemistry Research Institute , Xi'an Shaanxi , China
Published online: 04 Aug 2011.
To cite this article: Jianming Yang , Qinwei Yu , Fengwei Zhao , Jian Lu & Zhongxue Ge (2011)
Triacylperhydro-1,3,5-triazines over Phenylsulfonic Acid Functionalized Mesoporous Silica, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry,
41:23, 3455-3461, DOI: 10.1080/00397911.2010.517887
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1
Synthetic Communications , 41: 3455–3461, 2011
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2010.517887
TRIACYLPERHYDRO-1,3,5-TRIAZINES OVER
PHENYLSULFONIC ACID FUNCTIONALIZED
MESOPOROUS SILICA
Jianming Yang, Qinwei Yu, Fengwei Zhao, Jian Lu, and
Zhongxue Ge
Xi’an Modern Chemistry Research Institute, Xi’an Shaanxi, China
GRAPHICAL ABSTRACT
Abstract An operationally simple, efficient, and environmentally benign synthesis of
,3,5-triacylperhydro-1,3,5-triazines in good yields by reaction of different organic nitriles
1
and trioxane in the presence of phenylsulfonic acid functionalized mesoporous silica under
mild conditions was examined. The yields of the corresponding 1,3,5-trisubstituted
perhydro-s-triazines synthesized from acetonitrile, propionitrile, butyronitrile, benzonitrile,
and 1.3.5-trioxane were 95.7%, 96.1%, 84.2%, and 98.1%, respectively. The products were
1
characterized by H NMR, infrared, mass spectrometry, and elemental analysis. The mech-
anism of the formation of 1,3,5-triacylperhydro-1,3,5-triazines in acidic conditions was also
described using a model reaction of butyronitrile with trioxane.
Keywords Environmentally benign synthesis; nitrile; 1,3,5-triazines; solid acid
Received December 12, 2007.
Address correspondence to Jianming Yang, Xi’an Modern Chemistry Research Institute, 168
Zhangba Donglu, Xi’an Shaanxi, 710065, China. E-mail: yangjm204@163.com
3
455

3456
J. YANG ET AL.
INTRODUCTION
Substituted 1,3,5-triazines are of considerable importance as reinforcement pro-
[1,2]
moters in polymer chemical industry.
In addition, these compounds are used as a
key precursor for the synthesis of RDX (hexogen, trimethylene trinitramine) by
further nitration, so the syntheses of 1,3,5-triazines have been the subject of investiga-
tions. Generally, 1,3,5-triazine compounds have been prepared by reaction of organic
nitriles with polymeric formaldehyde such as paraformaldehyde or trioxane and an
aliphatic anhydride in the presence of sulfuric acid, p-toluenesulfonic acid, and
[3]
ion-exchange resins as catalysts. However, most of the procedures suffer from diffi-
culties separating catalyst from the reaction mixture, environmental problems, or ero-
sion problems. The acidic ion-exchange resins possess poor heat resistance and are
easily swollen in organic solvents for a longer time. The method described has proven
unsatisfactory for commercial usage because the reaction has been found to be uncon-
trollable and quite violent after an unpredictable and rather long induction period
upon scale-up. Therefore, an operationally simple, efficient, and environmentally
benign synthesis of these compounds that overcomes these deficiencies is in demand.
Recently, the use of sulfonic acid functionalized mesoporous silica has
[
4–8]
attracted great interests.
porous silica is a green, reusable, and versatile acidic catalyst in organic syntheses
We found that phenylsulfonic acid functionalized meso-
[
9–11]
such as esterification, ethericication, and condensation.
With the aim of obtain-
ing a more practical synthesis of this group of compounds, here we present a novel
modification of the synthesis of 1,3,5-triacylperhydro-1,3,5-triazines from 1,3,5-
trioxane (paraformaldehyde 1) and organic nitriles using a solid acid catalyst of phe-
nylsulfonic acid functionalized mesoporous silica (Scheme 1).
RESULTS AND DISCUSSION
The phenylsulfonic acid functionalized mesoporous silica is as reported in the
It belongs to the mesoporous material, with surface area of
[
10]
previous work.
7
2
22 m g , mean pore size of 14.3 nm, and pore volume of 0.59 mLg . The introduced
ꢀ1
ꢀ1
Scheme 1. Syntheses of 1,3,5-triacylperhydro-1,3,5-triazines from 1,3,5-trioxane (paraformaldehyde 1)
and nitriles.

CATALYTIC SYNTHESIS OF 1,3,5-TRIAZINES
3457
Table 1. Condensation of model reaction in various solvents
Entry
Solvents
Time (h)
Yield (%)
1
2
3
4
5
6
7
8
9
1,1,1-Trichloroethane
1,1,2-Trichloroethane
1,2-Dichloroethane
Tetrachloromethane
DMF
8
8
71.0
55.6
8
96.1
74.5
8
18
18
16
18
18
<10
<10
DMSO
DMI
<10
—
H
2
O
CS
2
Very low
sulfonic acid groups by sulfonation are highly dispersed in the precursor and bonded
on the meta-position of the phenyl ring, which covalently is anchored onto the
organic–inorganic hybrid material. So we use the prepared material as the catalyst
in our experiments.
Searching for the appropriate solvent is of important for successful syntheses.
First, a combination of propionitrile and trioxane is chosen a model for the reaction
of organic nitriles with trioxane. The reactions were carried out with propionitrile and
ꢁ
trioxane in a molar ratio of 4:1 in the presence of the catalyst at 80 C in various solvents
such as 1,1,1-trichloroethane, 1,2-dichloroethane, tetrachloromethane, dimethylforma-
mide (DMF), dimethylsulfoxide (DMSO), and 1,3-dimethyl-imidazolinone (DMI). The
results are summarized in Table 1. The results in Table 1 indicate that the crude products,
1,3,5-tripropionylperhydro-1,3,5-triazines, obtained with 1,2-dichloroethane have been
in every case superior to those obtained under any other conditions, and therefore they
are the better choice. However, strongly polar nonprotonic solvents as DMF, DMSO,
and DMI afford relatively poor yields of 1,3,5-triacylperhydro-1,3,5-triazines (entries
5
–9, Table 1), and a bulk of the staring material is recovered in the same conditions.
Having established the better reaction conditions, various 1,3,5-triacylperhydro-
,3,5-triazines are synthesized in good yields by reaction of different organic nitriles
1
with trioxane. Several representative titled compounds are summarized in Table 2.
In all cases of the organic nitriles, either the aliphatic nitriles or the aromatic
nitriles, as the starting materials, 1,3,5-triacylperhydro-1,3,5-triazines were the sole
products in better and more reproducible yields in dichloroethane (entries 1–4,
Table 2). The amides fail to give the corresponding 1,3,5-triazines when the reactions
ꢁ
are performed at 80 C within 18 h (entries 5–7), and the reason might be the poor
nucleophilicity of the amides. Unexpectedly, it has been found that the formation
of 1,3,5-triacylperhydro-1,3,5-triazines in condensation of organic nitriles with triox-
ane is relatively susceptible to moisture. To verify this finding, the experiment was
carried out in the presence of a slight trace of water, affording the corresponding
methyl-bisamides, as listed in Table 2 (entry 8). As far as cyanoacetamide is con-
cerned, the reaction does not proceed well in the same condition; moreover, the pro-
duct of the corresponding 1,3,5-triazine is unobtainable even if the reaction
ꢁ
temperature is raised to 140 C.
On the basis of the experimental results reported previously, a mechanism
for the condensation of organic nitriles with trioxane is proposed, as shown in
Scheme 2. First, trioxane 1 undergoes a tautermic process to form formaldehyde,

3458
J. YANG ET AL.
Table 2. Synthesis of the representative 1,3,5-triacylperhydro-1,3,5-triazines compounds
a
Entry
Nitrile R¼
CH
Molar ratio
Solvents
Products
Yield (%)
1
2
3
4
5
6
7
8
3
4:1
4:1
4:1
4:1
4:1
4:1
4:1
4:1
1,2-dichloroethane
1,2-dichloroethane
1,2-dichloroethane
1,2-dichloroethane
1,2-dichloroethane
1,2-dichloroethane
1,2-dichloroethane
1,2-dichloroethane
3a
3b
3c
3d
—
—
—
—
88.0
95.7
84.2
98.1
—
CH CH
CH CH
3
2
3
2
CH
2
Phenyl
CNCH CONH
CH CONH
CH CH CONH
Butyl
2
2
c
3
2
93.9
c
3
2
2
89.6
b
85.6
a
Isolated yields from solution.
The reaction is performed in the presence of a slight trace of water; the product is methyl bis-amides.
The yields of the starting materials recovered.
b
c
with protonization occurring in the presence of the acid catalyst, thus generating an
oxonium ion of formaldehyde and forming a carbonation ion 4 by a tautermic process.
The carbonation ion 4 suffers from a nucleophilic attack by the organic nitrile 2 and
gives rise to an adduct 5, which then transforms an acyl imide 6 through an electron-
transfer process and a deprotonation process. The intermidiate 6 are unstable in acidic
surroundings and readily to proceed to a cyclization reaction to afford the products
1
,3,5-triacylperhydro-1,3,5-triazines 3. When the reaction is performed in a moist
environment and the reactants are the butyronitrile and trioxane, the product methylene
bis-butyric acid amides will be generated. A plausible elucidation is shown in Scheme 3.
In conclusion, a novel and highly efficient approach to the synthesis of
1
,3,5-triacylperhydro-1,3,5-triazines by the condensation reaction of organic nitriles
with trioxane catalyzed by phenylsulfonic acid functionalized mesoporous silica has
been established. The method offers several significant advantages such as high con-
versions, easy handling, and a clean reaction profile, which make it a useful and
attractive process for the rapid synthesis of 1,3,5-triacylperhydro-1,3,5-triazines.
Scheme 2. Proposed mechanism of the formation of the 1,3,5-triacylperhydro-1,3,5-triazines.

CATALYTIC SYNTHESIS OF 1,3,5-TRIAZINES
3459
Scheme 3. Proposed mechanism of the formation of the methylene bis-butyric acid amide.
EXPERIMENTAL
Typical Procedure for Synthesis of 1,3,5-Tributyrylperhydro-
,3,5-triazines
1
To a solution of 11.0 g (0.16 mol) of freshly distilled butyronitrile in 70 mL of
dry 1,2-dichloroethane, 2 g of phenylsulfonic acid functionalized mesoporous silica
was added. Another solution of 11.0 g (0.16 mol) of butyronitrile and 7.2 g
(0.08 mol) of trioxane in 50 mL of 1,2-dichloroethane was added dropwise to the sol-
ution with stirring under reflux. After completion of the reaction, the catalyst was
filtered, and a white solid was precipitated, the filtrate being cooled to rt. The preci-
pitated solid was collected and recrystallized with cyclohexane to afford the product
with a purity of 99.51%.
1
13
H NMR and C NMR spectra were recorded on a Bruck Gemini 500-MHz
spectrometer, and chemical shifts are reported in d units (ppm) relative to tetra-
methylsilane (TMS) as an internal standard. Fourier transform infrared (FTIR)
spectra of all the products were recorded on a Nicolet spectrometer with KBr pellet
in the transmission. High-performance liquid chromatographic (HPLC) analyses
were carried out on a Varian liquid chromatograph (250 ꢂ 4.6 mm C18 column,
gradient elution 60% methanol and 40% H O, 1 mL=min, ultraviolet detection at
2
2
54 nm). All the regents used were of analytical reagent grade.
DATA
1,3,5-Triacetyclperhydro-1,3,5-triazines
ꢁ
1
Yield 88.0%, mp 70.3–71.8 C; H NMR (DMSO-d , 500 MHz), d: 2.12 (s, 9H,
6
1
3
CH ), 5.22 (s, 6H, N-CH -N); C NMR (DMSO-d , 125 MHz) d: 20.88, 55.98,
3
2
6
ꢀ þ
1
169.32; IR (KBr) 2970, 1635 cm ; ES=MS m=z (%): 213 (M ), 43 (100). Anal. calcd.
for C H O N : C, 50.70; H, 7.042; N, 19.61. Found: C, 50.61; H,7.031; N, 19.72.
9
15
3
3
1,3,5-Tripropionylperhydro-1,3,5-triazines
ꢁ
1
Yield 95.7%, mp 173.1–173.8 C; H NMR (DMSO-d , 500 MHz), d: 0.96–0.99
6
1
t, 9H, CH ), 2.45–2.51 (q, 6H, CH ), 5.23 (s, 6H, N-CH -N); C NMR (DMSO-d6,
3
(
3 2 2
1
25 MHz) d: 13.67, 34.66, 55.93, 172.25; IR (KBr) 2980, 2943, 2881, 1464, 1369,

3460
J. YANG ET AL.
ꢀ
1
650 cm ; ES=MS m=z (%): 255(M ), 57(100). Anal. calcd. for C H O N : C,
þ
1
5
1
2
21
3
3
6.47; H, 8.235; N, 16.47. Found: C, 56.51; H, 8.231; N, 16.41.
1,3,5-Tributyrylperhydro-1,3,5-triazines
ꢁ
1
Yield 84.2%, mp: 69.2–79.2 C; H NMR (DMSO-d , 500 MHz), d: 0.94–0.97
6
(
t, 3H, CH ), 1.61–1.69 (q, 2H, CH ), 2.49–2.52 (t, 2H, CH ), 5.28 (s, 6H, N-CH -
3
3 2 2 2
1
N); C NMR (DMSO-d , 125 MHz) d: 13.67, 18.21, 34.66, 55.93, 172.25; IR
6
ꢀ
1
KBr) 2960, 2934, 2873, 1466, 1649 cm ; ES=MS m=z (%): 297 (M ), 43 (100). Anal.
þ
(
calcd. for C H O N : C, 60.61; H, 9.091; N, 14.14. Found: C, 60.54; H, 9.085; N,
1
5
27
3
3
1
4.09.
1,3,5-Tribenzoylperhydro-1,3,5-triazines
ꢁ
1
Yield 98.1%, mp: 220.3–223.0 C; H NMR (DMSO-d , 500 MHz), d: 5.33 (s,
6
1
3
6
1
7
H, N-CH -N), 7.36–7.42 (m, 15H, aromatic); C NMR (DMSO-d , 125 MHz) d:
2 6
27.33, 128.34, 130.52, 133.67, 169.18; IR (KBr) 3034, 3058, 1670, 1649, 1601,
þ
ꢀ1
21, 697 cm ; ES=MS m=z (%): 398 (M ꢀ 1), 105 (100). Anal. calcd. for
C H O N : C, 72.62; H, 5.61; N, 10.16. Found: C, 71.60; H, 5.60; N, 10.15.
3
2
5
23
3
Methylene Bis-butyric Acid Amide
ꢁ
1
Yield 85.6%, mp: 181.3–182.5 C; H NMR (DMSO-d , 500 MHz), d:
6
0
.92–0.95 (t, 3H, CH ), 1.61–1.69 (q, 2H, CH ), 2.14–2.17 (t, 2H, CH ), 4.57–4.60
3 2 2
1
3
(t, 1H, N-CH -N), 6.93 (s, 1H, CH -NH-CO); C NMR (DMSO-d , 125 MHz) d:
2 2 6
ꢀ
1
1
3.79, 19.04, 38.35, 44.65, 174.39; IR (KBr) 2960, 2934, 2873, 1466, 1649 cm
þ
;
ES=MS m=z (%): 173.2(M þ 1), 43 (100). Anal. calcd. for C H O N : C, 55.79;
8
16
2
2
H, 9.36; N, 14.27. Found: C, 55.83; H, 9.34; N, 14.23.
ACKNOWLEDGMENT
Financial support from the Major State Basic Research Foundation
Department of Equipment, China, is grateful acknowledged.
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