Facile N-nitrosation of secondary amines using poly(N,N'-dibromo-Nethylene- benzene-1,3-disulfonamide) and N,N,N′,N′-tetrabromobenzene-1,3- disulfonamide/NaNO2 under mild conditions

Article abstract of DOI:10.2174/1570178611310030011

In this research project, a combination of poly(N,N′-dibromo-N- ethylene-benzene-1,3-disulfonamide) [PBBS] and/or (N,N,N′,N′- tetrabromobenzene-1,3-disulfonamide) [TBBDA] with sodium nitrite in the presence of wet SiO₂ (50% w/w) was used as an efficient nitrosating agent for the conversion of secondary amines to their corresponding nitroso compounds. N-Nitrosation reaction has been performed in dichloromethane at room temperature under mild and heterogeneous conditions. The reaction is operationally simple and corresponding products were achieved in good to excellent yields.

Full text of DOI:10.2174/1570178611310030011

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204
Letters in Organic Chemistry, 2013, 10, 204-208
Facile N-Nitrosation of Secondary Amines Using Poly(N,N'-dibromo-N-
ethylene-benzene-1,3-disulfonamide) and N,N,Nꢀ,Nꢀ-tetrabromobenzene-
1,3-disulfonamide/NaNO2 Under Mild Conditions
Ramin Ghorbani-Vaghei*,a, Lotfi Shiria and Arash Ghorbani-Choghamaranib
aDepartment of Organic Chemistry, Faculty of Chemistry, Bu-Ali Sina University, P. O. Box 6517838683, Hamedan,
Iran
bDepartment of Chemistry, Faculty of Sciences, Ilam University, P.O. Box 69315516, Ilam, Iran
Received December 31, 2012: Revised February 20, 2013: Accepted February 25, 2013
Abstract: In this research project, a combination of poly(N,Nꢀ-dibromo-N-ethylene-benzene-1,3-disulfonamide) [PBBS]
and/or (N,N,Nꢀ,Nꢀ-tetrabromobenzene-1,3-disulfonamide) [TBBDA] with sodium nitrite in the presence of wet SiO2 (50%
w/w) was used as an efficient nitrosating agent for the conversion of secondary amines to their corresponding nitroso
compounds. N-Nitrosation reaction has been performed in dichloromethane at room temperature under mild and heteroge-
neous conditions. The reaction is operationally simple and corresponding products were achieved in good to excellent
yields.
Keywords: Poly (N,Nꢀ-Dibromo-N-ethylene-benzene-1,3-disulfonamide) [PBBS], N,N,Nꢀ,Nꢀ-Tetrabromobenzene-1,3-
disulfonamide [TBBDA], N-Nitrosation, N-Nitrosamines, Sodium nitrite, Wet SiO2.
INTRODUCTION
conditions [12], silica sulfuric acid [13], oxyhyponitrite [14],
tungstate sulfuric acid [15], trichloroisocyanuric acid [16],
trichloromelamine [17], Nafion-H® [18], 1,3-dihalo-5,5-
dimethylhydantion [19], molybdate sulfuric acid [20], 1,3,5-
triazine-2,4,6-triyltrisulfamic acid [21], with sodium nitrite
have also been reported.
Nitrosation chemistry has been introduced as an attrac-
tive area in the study of organic reaction mechanism and
biological sciences [1]. Many researchers have attempted to
introduce both the synthetic and mechanistic aspects of ni-
trosation or transnitrosation [2,3,10-21]. N-Nitrosation of
amines is an important and well-known reaction in organic
synthesis. Recently, N-Nitrosamines have been considered
mainly due to their strong mutagenic and carcinogenic prop-
erties. It has been found that these compounds have vasore-
laxant activity and used as pesticides, antioxidants and lubri-
cant additives [4]. N-Nitrosamines are also usable as syn-
thetic intermediates for the preparation of various N,N-
bonded functionalities. Moreover, due to their facile lithia-
tion, followed by reaction with electrophile groups and sub-
sequent denitrosation, they can be used in the electrophilic
substitution of secondary amines at the ꢁ-carbon in a regio-
and stereoselective manner [5]. A hindered rotation about the
N-N bond, being a consequence of partial double-bond char-
acters between two adjacent nitrogens, results in many fasci-
nating stereochemical forms of this class of compounds
[6,7]. The most general reagent for synthesis of nitro-
soamines is nitrous acid which is produced in situ from so-
dium nitrite and mineral acid in water or in mixed alcohol-
water solvents [8, 9]. Some other nitrosating agents, such as
fremy’s salt [10], bis(triphenylphosphine)nitrogen(1+) nitrite
[11], N-haloamides and sodium nitrite under phase-transfer
RESULTS AND DISCUSSION
In continuation of our studies about organic functional
group transformations, we have found that N,N,N',N'-
tetrabromobenzene-1,3-disulfonamide
[TBBDA]
and
poly(N,N'-dibromo-N-ethylene-benzene-1,3-disulfonamide)
[PBBS] have advantages and applications in the organic
transformations [22-29]. Therefore, we decided to apply
TBBDA and PBBS in combination with sodium nitrite and
wet SiO2 (50% w/w) as highly reactive reagents for the ni-
trosation of secondary amines in CH2Cl2 as solvent at room
temperature under mild conditions (Scheme 1).
In order to optimize the reaction conditions, we examined
the effect of different molar ratios of (TBBDA) or (PBBS)
and sodium nitrite in CH2Cl2 at room temperature for the
conversion of dibenzylamine to N-nitrosodibenzylamine, as
a model reaction. We found that the best molar ratio for the
total conversion of dibenzylamine to N-nitrosodi-
benzylamine was [(1 mmol/2 mmol/0.5 g) (amine/sodium
nitrite/PBBS)] and [(1 mmol/2 mmol/0.35 mmol)
(amine/sodium nitrite/TBBDA)]; the results are summarized
in Table 1.
*Address correspondence to this author at the Department of Organic
Chemistry, Faculty of Chemistry, Bu-Ali Sina University, P. O. Box
6517838683, Hamedan, Iran; Tel: 98 811 8254707; Fax: 98 811 8254707;
E-mail: rgvaghei@yahoo.com
This method is general and can be easily applied for the
conversion of a variety of commercially available secondary
1875-6255/13 $58.00+.00
© 2013 Bentham Science Publishers

N-Nitrosation of Secondary Amines
Letters in Organic Chemistry, 2013, Vol. 10, No. 3 205
PBBS and/orTBBDA/NaNO2
CH2Cl2, Wet SiO2, r.t
R1R2N-N=O
2
R1R2NH
1
Br
Br
N
Br
Br
N
CH2
CH2
)
Br
N
(
N
Br
n
S
S
S
S
O
O
O
O
O
O
O
O
PBBS
TBBDA
Scheme 1.
Table 1. N-Nitrosations of Dibenzylamine Using Different Amounts of TBBDA and Sodium Nitrite in Dichloromethane at Room
Temperature.a
TBBDA/NaNO2
(PhCH2)2NH
(PhCH2)2N-NO
CH2Cl2,Wet SiO2,RT
Entry
TBBDA (mmol)
NaNO2(mmol)
Yield(%)b
1
2
3
4
5
0.35
0.35
0.35
0.25
0.30
2
1.5
2
40
175
98
2
50
2
70
a Reaction conditions: amine (1 mmol), NaNO2 (2 mmol), TBBDA (0.35 mmol), wet SiO2 (50% w/w) (0.5 g), 5 min.
b Isolated yield.
Table 2. N-Nitrosation of Secondary Amines to their Corresponding N-nitrosoamines with a Combination of TBBDA/NaNO2 or
PBBS/NaNO2 in the Presence of Wet SiO2 (50% w/w) in Dichloromethane at Room Temperature
TBBDA
PBBS
Entry
Substrate
Producta
Time yield
(min) (%)b
Time yield
(min) (%)b
1
2
3
4
Et2NH
Et2N-N=O
(i -Pr)2N-N=O
(C6H13)2N-N=O
3
4
3
85
85
96
4
3
3
83
80
93
(i -Pr)2NH
(C6H13)2NH
N H
N-N=O
9
89
85
95
3
3
5
92
90
95
5
6
O
NH
NH
O
N-N=O
7
HN
O=N-N
N-N=O
10
7
8
(C6H11)CH3NH
(C6H11)2NH
(C6H11)CH3N-N=O
(C6H11)2N-N=O
4
5
5
3
98
98
98
95
3
5
5
3
97
98
96
94
9
(PhCH2)2NH
(PhCH2)2N-N=O
CH3(PhCH2)N-N=O
10
CH3(PhCH2)NH

206 Letters in Organic Chemistry, 2013, Vol. 10, No. 3
Ghorbani-Vaghei et al.
Table 2. contd…
TBBDA
PBBS
Entry
Substrate
Producta
Time yield
(min) (%)b
Time yield
(min) (%)b
11
12
13
14
15c
CH3CH2(PhCH2)NH
(CH3)2CH(PhCH2)NH
(CH3)3C(PhCH2)NH
Ph(PhCH2)NH
CH3CH2(PhCH2)N-N=O
(CH3)2CH(PhCH2)N-N=O
(CH3)3C(PhCH2)N-N=O
Ph(PhCH2)N-N=O
5
90
95
97
90
-
5
5
5
5
93
97
95
85
-
3
3
4
(PhCH2)2NH
(PhCH2)2N-N=O
60
60
a All of the isolated products are known and their spectra and physical data have been reported in the literature [1-15,20,21].
b Isolated yield.
c Reaction in absence of Wet SiO2 (50% w/w).
TBBDA/NaNO2
NH
O=N-N
N-N=O
+
ON-N
HN
NH
CH2Cl2, Wet SiO2, RT
0%
100%
Br
Scheme 2.
Br
N
Br
Br
Br
N
Br
N
Br
+HOBr
+ H2O(wet)
N
S
O
H
S
S
S
O
O
O
O
O
O
O
HOBr + NaNO2
HOBr + HNO2
HNO2 + NaOBr
H2O + NO+ + BrO-
R2N-NO + H3O+
R2NH + NO+ + H2O
H3O+
+ BrO-
H2O + HOBr
Scheme 3.
amines to their N-nitrosoamines. The results including times
and yields of reactions are given in Table 2.
SiO2 (50% w/w). Therefore, the possible mechanism for the
conversion of secondary amines to their corresponding N-
nitroso compounds has been shown in Scheme 3 based on
previously reported work [19].
An interesting phenomenon happened during our N-
nitrosation studies. Dinitrosation of piperazine (1f) occurred
easily using the appropriate molar ratio of the reagents, but
any attempt to achieve mononitroso piperazine failed. With-
out any separation by chromatography method, several at-
tempts to produce pure mononitrosamine as the single prod-
uct, unfortunately failed (Scheme 2).
To demonstrate the efficiency of this method, the results
of N-nitrosation of dicyclohexyl amine by the present
method are compared with the best of the well-known data
from the literature as outlined in the Table 3.
As it is evident from Table 3, our nitrosating system is
superior to some previously reported procedures.
Since TBBDA and PBBS contain bromine atoms, which
are attached to nitrogen atoms; therefore these reagents re-
lease in situ Br+, which can act as an electrophilic species.
Wet SiO2 (50% w/w) provides an effective heterogeneous
surface area for in situ generation of HNO2 and also makes
the reaction work-up easier. In order to show the role of wet
SiO2 (50% w/w), we designed a reaction in the absence of
this compound (Entry 15, Table 2), and it was observed that
the nitrosation reaction did not occur in the absence of wet
In conclusion, a new protocol has been delineated for the
preparation of N-nitroso secondary amines by an efficient
heterogeneous media including poly(N,Nꢀ-dibromo-N-
ethylbene-benzene-1,3-disulfonamide)
[PBBS]
and/or
(N,N,Nꢀ,Nꢀ-tetrabromobenzene-1,3-disulfonamide)
[TBBDA], sodium nitrite and wet SiO2 (50 % w/w) . Fur-
thermore, this procedure exhibits mild reaction conditions,
short reaction times and experimental convenience.

N-Nitrosation of Secondary Amines
Letters in Organic Chemistry, 2013, Vol. 10, No. 3 207
Table 3. Comparison of N-nitrosation of Dicyclohexyl Amine By the Described System with some of those Reported in the Literature.
Molar Ratio
Reagent/NaNO2
Reagent
Time (min)
Yield (%)a
Trichloromelamine
Trichloroisocyanuric acid
DBDMH
1/3.5
0.7/2.1
0.6/2
15
25
5
9217
9916
8619
8719
98
DCDMH
0.6/2
5
TBBDA
0.35/2
0.5g/2
5
PBBS
5
98
a Isolated yield.
EXPERIMENTAL
General Method
(aliph.CH), 1495, 1585, 1600 (arom.C=C), 1455 (N=O),
1316 (C-N), 1071 (N-N) cm-1; 1H NMR (90 MHz, CDCl3): ꢁ
= 7.23-7.43 (m, 10H), 5.18 (s, 2H), 4.64 (s, 2H) ppm.
Poly(N,Nꢀ-dibromo-N-ethylene-benzene-1,3-disulfona-
mide) [PBBS] and (N,N,Nꢀ,Nꢂ-tetrabromobenzene-1,3-di-
sulfonamide) [TBBDA] have been prepared via our previ-
ously reported procedure [22].All chemicals were purchased
from Fluka, Merck and Aldrich chemical companies and
used without further purification. N-Nitrosamine products
were characterized by comparison of their spectral (IR and
1H NMR) and physical data with authentic samples.
N-Nitroso-N-tert-butyl benzyl amine: Pale yellow solid.
Mp 43-45ꢃC; IR (KBr): ꢄ = 3031-3063 (arom.CH), 2932-
2980 (aliph.CH), 1496, 1603 (arom.C=C), 1434 (N=O),
1321 (C-N), 1164 (N-N) cm-1; 1H NMR (90 MHz, CDCl3): ꢁ
= 7.14-7.42 (m, 5H), 4.76 (s, 2H), 1.53 (s, 9H) ppm.
CONFLICT OF INTEREST
Cautions: All N-nitrosoamines [R1-N(NO)-R2] should be
regarded as potentially powerful carcinogen [8].
The author(s) confirm that this article content has no con-
flict of interest.
General Procedure for N-nitrosation of Secondary Amines
with TBBDA and PBBS
ACKNOWLEDGEMENTS
To a stirred solution of amine (1 mmol) in CH2Cl2 (5
mL), NaNO2 (2 mmol), wet SiO2 (50% w/w, 0.2 g) and
PBBS (0.5 g) or TBBDA (0.35 mmol) were added. The het-
erogeneous reaction mixture was stirred at room temperature
for appropriate time (Table 2). After completion of the reac-
tion [the reaction progress was monitored by TLC (n-
hexane:ethyl acetate 8:2)], the reaction mixture was filtered
and washed with dichloromethane (2ꢀ5 mL). Then anhy-
drous Na2SO4 (2 g) was added and filtered off. Dichloro-
methane was removed by reduced pressure and N-
nitrosamines were obtained (Table 2). For further purifica-
tion column chromatography on silica gel (n-hexane:ethyl
acetate 8:2) was used.
We are thankful to Bu-Ali Sina University, Center of Ex-
cellence in Development of Environmentally Friendly Meth-
ods for Chemical Synthesis (CEDEFMCS) for financial sup-
port.
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