Intramolecular interaction between ortho-azido and azoxy groups as a new way of forming a N-N bond. Synthesis of 2-alkylbenzotriazole 1-oxides

Article abstract of DOI:10.1007/s11172-005-0350-0

Heating of 2-(alkyl-NNO-azoxy)-1-azidobenzenes in boiling benzene gave 2-alkyl-benzotriazole 1-oxides (Alk = Me, Et, Prⁱ, and Bu ^t). This first-order reaction involves an earlier unknown intramolecular interaction between the azido and azoxy groups with simultaneous release of molecular nitrogen. The cyclization rate increases in the following sequence of the alkyl groups: Me < Et < Prⁱ < Bu ^t. Complete assignment of the signals in the ¹H, ¹³C, and ¹⁴N NMR spectra of 2-alkylbenzotriazole 1-oxides was performed.

Full text of DOI:10.1007/s11172-005-0350-0

Russian Chemical Bulletin, International Edition, Vol. 54, No. 4, pp. 1013—1020, April, 2005
1013
Intramolecular interaction between orthoꢀazido and azoxy groups
as a new way of forming a N—N bond.
Synthesis of 2ꢀalkylbenzotriazole 1ꢀoxides*
ꢀ
D. L. Lipilin, E. E. Karslyan, A. M. Churakov, Yu. A. Strelenko, and V. A. Tartakovsky
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
4
7 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (095) 135 5328. Eꢀmail: churakov@ioc.ac.ru
Heating of 2ꢀ(alkylꢀNNOꢀazoxy)ꢀ1ꢀazidobenzenes in boiling benzene gave 2ꢀalkylꢀ
i
t
benzotriazole 1ꢀoxides (Alk = Me, Et, Pr , and Bu ). This firstꢀorder reaction involves an
earlier unknown intramolecular interaction between the azido and azoxy groups with simultaꢀ
neous release of molecular nitrogen. The cyclization rate increases in the following sequence of
i
t
1
13
the alkyl groups: Me < Et < Pr < Bu . Complete assignment of the signals in the H, C, and
14
N NMR spectra of 2ꢀalkylbenzotriazole 1ꢀoxides was performed.
Key words: azides; azoxy compounds; nitrogenꢀcontaining heterocycles; Nꢀoxides of hetꢀ
1
13
14
erocycles; benzotriazoles; cyclization; H, C, and N NMR spectroscopy; synthetic methods.
Thermolysis of oꢀnitrophenylazides yields benzoꢀ
diazonium salts 2a—f with sodium azide gave the starting
1ꢀazidoꢀ2ꢀ(alkylꢀNNOꢀazoxy)benzenes 3a—f (Scheme 1).
furoxanes, with accompanying evolution of nitrogen. This
1
reaction is well studied. Apparently, its mechanism inꢀ
volves a cyclic transition state in which the lone electron
pair of the O atom of the nitro group attacks the electroꢀ
philic N atom of the azido group in the plane of the
molecule, while the aromatic character of the resulting
compound is due to the overlap of the πꢀorbitals and the
lone electron pair of the azido group in the perpendicular
plane.2
Scheme 1
In the present work, we studied an intramolecular
interaction between azido and azoxy groups ortho to each
other. The azoxy group is isoelectronic with the nitro
group; as expected, the mechanism of the reaction studꢀ
ied is analogous to the formation of benzofuroxanes, exꢀ
cept that the resulting bond is N—N rather than N—O.
Preparation of the starting reagents. Diazonium salts
were synthesized by diazotization of 2ꢀ(alkylꢀNNOꢀ
azoxy)anilines 1a—f with nitrosonium tetrafluoroborate
Compound(s) 1—3
R
X1
X2
a
b
c
d
e
f
Me
Et
H
H
H
H
H
Br
H
H
H
H
Br
H
3
according to earlier described procedures. Treatment of
i
Pr
*
Dedicated to Corresponding Member of the Russian Acadꢀ
emy of Sciences E. P. Serebryakov on the occasion of his
0th birthday.
But
t
Bu
But
7
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 989—996, April, 2005.
066ꢀ5285/05/5404ꢀ1013 © 2005 Springer Science+Business Media, Inc.
1

1
014
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 4, April, 2005
Lipilin et al.
Aniline 1b was obtained from compound 4 by reducꢀ
Scheme 4
tion of the nitro group (Scheme 2). Compound 4 was
synthesized by treatment of 1ꢀnitroꢀ2ꢀnitrosobenzene with
ethylamine hydrochloride in the presence of dibromoꢀ
isocyanuric acid. Analogous syntheses of anilines 1a and
4
,5
1
c—f were described earlier.
Scheme 2
Table 1. Synthesis of benzotriazole 1ꢀoxides 6a—g by cyclizaꢀ
a
tion of azidobenzenes 3a—g
Starting
reagent
Product
R
X1 X2 tb/h Yieldc M.p.
(%) /°C
3
3
3
3
3
3
3
a
b
c
d
e
f
6a
6b
6c
6d
6e
6f
Me
Et
H
H
H
H
H
H
H
H
H
Br
H
H
8
7
6
4
4
4
98 95—97d
95 92—94
93 90—93
95 96—98e
98 92—94
98 86—88
i
Pr
Bu
But
t
t
Bu Br
Azidobenzene 3g was obtained by treatment of chloro
But NO2
g
6g
0.5 99 127—129
derivative 5 with sodium azide in DMF at room temperaꢀ
ture (Scheme 3).
a
b
c
Benzene, 80 °C.
Reaction duration.
The yield was determined from H NMR data.
Cf. Ref. 6: m.p. 96 °C.
Cf. Ref. 7: m.p. 97—98 °C.
1
d
e
Scheme 3
a
Table 2. Rate constants of the cyclization of azidobenzenes 3
into benzotriazole 1ꢀoxides 6
4
–1
Starting
reagent
Product
k•10 /s
3
3
3
3
3
a
b
c
d
g
6a
6b
6c
6d
6g
0.65±0.04
0.78±0.08
1.00±0.12
1.46±0.08
15.0±0.3
All new compounds were identified by H, 13C, and
1
14
N NMR spectra with completely assigned signals (see
Experimental).
Cyclization of 1ꢀazidoꢀ2ꢀazoxybenzenes 3. Heating of
azidobenzenes 3a—g in boiling benzene was accompaꢀ
nied by nitrogen evolution, giving rise to the correspondꢀ
ing 2ꢀalkylbenzotriazole 1ꢀoxides 6a—g in virtually quanꢀ
titative yields (Scheme 4, Table 1).
aBenzene, 80 °C.
The data in Table 2 provide clear evidence that the
cyclization rate increases in parallel with the electronꢀ
donating properties of the alkyl group in the following
1
The cyclization process was monitored by H NMR
i
t
spectroscopy (concentrations of the starting reagents and
the reaction products were determined by integration of
signals for the corresponding alkyl groups). It was found
that the reaction obeys the firstꢀorder kinetic equation.
The rate constants (Table 2) were calculated by integrated
method of substitution (for compound 3a, the rate conꢀ
stant was determined in two independent experiments
over three and seven points; for the other compounds, in
one experiment over six points).
order: Me < Et < Pr < Bu . Accordingly, the distal N atom
of the azoxy group can be regarded as a nucleophilic
reactive center. Since introduction of a nitro group into
the paraꢀposition relative to the azido group accelerates
the reaction almost 10 times, the azido group can be
considered to be an electrophilic reactive center. Hence,
the cyclization mechanism seems to be similar to the
thoroughly studied mechanism of the formation of benzoꢀ
furoxanes 8 in the thermolysis of 2ꢀazidoꢀ1ꢀnitrobenꢀ

2
ꢀAlkylbenzotriazole 1ꢀoxides
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 4, April, 2005
1015
1
zenes 7, except that the latter cyclization involves the
O atom as a nucleophilic center (Scheme 5).
Scheme 5
azide 3f into Nꢀoxide 6f rather than Nꢀimine 9a is probꢀ
ably due to a large energy difference between these comꢀ
–
1
pounds (~50 kcal mol , which is of the same order as the
difference between compounds 6a and 9b).
A priori, the oxygen atom could also be a nucleophilic
center in the cyclization of 1ꢀazidoꢀ2ꢀazoxybenzenes 3 as
well. In this case, in the cyclization of, e.g., compound 3f,
Nꢀimine 9a would be a reaction product, which could
undergo ring opening to give orthoꢀnitrosoazobenzene 10a
followed by recyclization into thermodynamically more
stable Nꢀoxide 6e (Scheme 6). The bromine atom that is
meta to nitrogen bearing the Nꢀoxide oxygen atom in the
starting compound 3f would occupy the paraꢀposition
with respect to such a N atom in reaction product 6e.
To verify that the sequence 9a → 10a → 6e is thermoꢀ
dynamically favorable, we performed HF/6ꢀ31G calculaꢀ
tions of the total energies of model compounds 6a, 9b,
and 10b.
To compare the cyclization rates of compounds 3d
(intramolecular interaction between the azido and azoxy
groups) and 7 (intramolecular interaction between the
azido and nitro groups), we carried out the following kiꢀ
netic experiment. A solution of equal amounts of comꢀ
pounds 3d and 7 in benzene and toluene was heated.
Their concentration changes were monitored by recordꢀ
14
ing N NMR spectra of periodically withdrawn samples
and measuring the integral intensities of the signals for
the nitro and azoxy groups. Construction of a linear relaꢀ
tionship between the concentrations of the starting reꢀ
agents and leastꢀsquares determination of the ratio of their
8
rate constants showed that the cyclization rate of 2ꢀazidoꢀ
However, one can unambiguously state that the hypoꢀ
thetical process 3f → 9a → 10a → 6e does not occur in
reality since the thermolysis of azidoazoxybenzene 3f gives
Nꢀoxide 6f, in which the bromine atom is again meta to
the nitrogen atom bound to the Nꢀoxide oxygen atom, as
in the starting compound 3f. Note that benzotriazole
1ꢀ(tertꢀbutylꢀNNOꢀazoxy)benzene 3d is 1.4 times higher
than that of 2ꢀazidoꢀ1ꢀnitrobenzene 7.
Laboratory preparation of 2ꢀalkylbenzotriazole 1ꢀoxꢀ
9
ides. 2ꢀArylbenzotriazole 1ꢀoxides are widely known and
1
0
their biological activities have been studied in detail. In
contrast, 2ꢀalkyl analogs are not easily accessible and have
been synthesized only in a few studies.6
,11,12
1
ꢀoxide 6f was identified unambiguously. Cyclization of
Scheme 6

1
016
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 4, April, 2005
Lipilin et al.
7
Previously, we reported that oxidation of 2ꢀ(tertꢀbuꢀ
in the synthesis of benzotriazole 1ꢀoxides with electronꢀ
withdrawing substituents in the benzene ring.
tylazo)aniline 11a with perbenzoic acid affords 2ꢀ(tertꢀbuꢀ
tyl)benzotriazole 1ꢀoxide (6d). Using a modified proceꢀ
dure, we increased the yield of this reaction to 95%. Howꢀ
ever, the oxidation of 4ꢀbromoaniline 11b gave benzoꢀ
triazole 1ꢀoxide 6e only in 49% yield and some byꢀprodꢀ
ucts were obtained (Scheme 7).
Laboratory preparation of 2ꢀalkylbenzotriazole 1ꢀoxꢀ
ides 6 from azoxyanilines 1 can be simplified by carrying
out the reactions without isolating intermediate products.
Such a possibility was illustrated with the transformation
1d → 6d in 62% yield.
Alternatively, laboratory preparation of 2ꢀalkylbenzoꢀ
triazole 1ꢀoxides with electronꢀwithdrawing substituents
can be simplified by using 2ꢀchloroꢀ1ꢀazoxybenzenes as
starting reagents. For instance, 6ꢀnitrobenzotriazole
Scheme 7
1
ꢀoxide 6g was obtained in one step from chloro derivaꢀ
tive 5 in 92% yield without isolation of intermediate
azidobenzene 3g (Scheme 8).
Scheme 8
Spectroscopic studies of 2ꢀalkylbenzotriazole 1ꢀoxides.
1
Complete signal assignment in the H (Tables 3, 4),
13
14
C (Table 5), and N NMR spectra (Table 6) of 2ꢀalkylꢀ
benzotriazole 1ꢀoxides was accomplished. The mass specꢀ
tra (EI, 70 eV) of these compounds contain a distinct
molecular ion peak.
Thus, we studied a new intramolecular cyclization of
azido and alkylꢀNNOꢀazoxy groups ortho to each other.
The cyclization rate increases with an increase in both the
electronꢀdonating properties of the alkyl group and the
electronꢀwithdrawing properties of the substituent para to
the azido group. This reaction provides a new way of
forming a N—N bond. The reaction can be used for laboꢀ
Taking into account that azoanilines 11 are prepared
by reduction of the corresponding azoxyanilines 1, this
route to 2ꢀalkylbenzotriazole 1ꢀoxides has no advantages
1
3
1
Table 3. H NMR spectra (300 MHz, δ, J/Hz) of benzotriazole 1ꢀoxides 6a—g
Comꢀ
pound
Alk
X
Solvent
H(4)
H(5)
H(6)
H(7)
Alk
6
6
a
b
Me
Et
—
—
CD Cl
7.68
7.70
7.39
7.41
7.30
7.32
7.68
7.70
4.22 s
1.55 (t, J = 7.4);
2
2
2
CD Cl
2
4
.65 (q, J = 7.4)
6
c
Pri
—
CD Cl
7.70
7.39
7.30
7.70
1.60 (d, J = 7.2);
.48 (hept, J = 7.2)
1.87 s
2
2
5
t
6
6
d
e
Bu
Bu
—
5ꢀBr
CD Cl
7.68
7.37
—
7.29
7.34 (dd,
J = 8.8, J = 1.3) J = 8.8)
7.66
7.57 (d,
2
2
2
t
CD Cl
7.87 (d,
J = 1.3)
7.57 (d,
J = 8.5)
7.97 (d,
J = 8.6)
1.85 s
2
6
6
f
But
6ꢀBr
CD Cl
7.41 (dd,
J = 8.5, J = 1.8)
8.19 (dd,
—
—
7.86 (d,
J = 1.8)
8.58 (d,
J = 1.7)
1.85 s
1.91 s
2
2
g
But 6ꢀNO2 Acetoneꢀd6
J = 8.6, J = 1.7)

2
ꢀAlkylbenzotriazole 1ꢀoxides
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 4, April, 2005
1017
Table 4. Spinꢀspin coupling constants (Hz) in the ABCDꢀtype
H NMR spectra of benzotriazole 1ꢀoxides 6a—d
toring by TLC); the precipitate of cyanuric acid was filtered off
and the filtrate was concentrated in vacuo. The product was
extracted with CH Cl and purified on a thin layer of silica gel
1
2
2
with benzene as an eluent. The yield of compound 4 as a redꢀ
orange oil was 374 mg (64%). Found (%): C, 49.19; H, 4.61;
N, 21.39. C H N O . Calculated (%): C, 49.23; H, 4.65;
J/Hz
6a
6b
6c
6d*
i
t
(
Alk = Me) (Alk = Et) (Alk = Pr ) (Alk = Bu )
8
9
3
3
3
–1
JH(4),H(5)
JH(4),H(6)
JH(5),H(6)
JH(5),H(7)
8.7
0.8
7.2
1.2
8.5
8.5
1.1
6.5
0.9
8.3
8.6
1.1
6.7
1.1
8.6
8.8
0.9
6.7
1.0
8.7
N, 21.53. IR (KBr), ν/cm : 1492 (N→O); 1360, 1540 (NO ).
2
4
1
H NMR (acetoneꢀd ), δ: 1.34 (t, 3 H, CH , J = 7.4 Hz); 3.65
6
3
3
(q, 2 H, CH , J = 7.4 Hz); 7.81—7.91 (m, 3 H, Ar); 8.07 (dd,
2
4
13
1 H, Ar, J = 8.8 Hz, J = 1.5 Hz). C NMR (acetoneꢀd ), δ:
6
3J
H(6),H(7)
11.8 (CH ); 48.2 (CH ); 125.8 (CH); 126.3 (CH); 132.4 (CH);
3
2
1
4
1
34.8 (CH); 142.5; 144.1. N NMR (acetoneꢀd ), δ: –14
6
* 5
JH(4),H(7) = 1.0 Hz.
(∆ν1/2
m/z: 195 [M] .
= 70 Hz, NO ); –55 (∆ν
= 40 Hz, N(O)=N). MS,
1/2
2
+
ratory preparation of not easily accessible 2ꢀalkylbenzoꢀ
triazole 1ꢀoxides.
1ꢀ(2ꢀAminophenyl)ꢀ2ꢀethyldiazene 1ꢀoxide (1b). A solution
of SnCl •2H O (1.9 g, 8.4 mmol) in conc. HCl (2 mL) was
2
2
added to a stirred solution of nitro compound 4 (390 mg, 2 mmol)
in ethanol (9 mL). The reaction mixture was stirred for 4 h and
poured into water. The product was extracted with ethyl acetate
Experimental
and the extract was dried with MgSO . The solvent was removed
4
IR spectra were recorded on a Specord Mꢀ80 spectrometer.
1H, 13C, and N NMR spectra were recorded on a Bruker
AMꢀ300 instrument (300.13, 75.5, and 21.5 MHz, respectively).
Chemical shifts in the 14N NMR spectra are given on the δ scale
and the residue was purified on a thin layer of silica gel with
CHCl3 as an eluent. The yield of azoxyaniline 1b as orange
crystals was 240 mg (73%), m.p. 32—34 °C. Found (%): C, 58.39;
H, 6.68; N, 25.25. C H N O. Calculated (%): C, 58.17; H, 6.71;
14
8
11
3
–
1
and referenced to MeNO ; upfield shifts are negative. Mass
N, 25.44. IR (KBr), ν/cm : 1496 (N→O); 3330, 3450 (NH ).
2
2
1
spectra were recorded on a Kratos MSꢀ300 instrument (EI,
H NMR (acetoneꢀd ), δ: 1.40 (t, 3 H, CH , J = 7.1 Hz); 3.69
6
3
7
0 eV); for bromineꢀcontaining fragments, only signals with the
Br isotope are given. The course of the reactions was moniꢀ
(q, 2 H, CH , J = 7.1 Hz); 6.67 (dt, 1 H, H(4), J = 8.3 Hz, J =
2
7
9
1.3 Hz); 6.96 (dd, 1 H, H(6), J = 8.3 Hz, J = 1.2 Hz); 7.25 (dt,
1 H, H(5), J = 8.4 Hz, J = 1.2 Hz); 7.96 (dd, 1 H, H(3), J =
tored by TLC (Silufol UVꢀ254). The earlier described proceꢀ
dures were used to prepare 1ꢀ(2ꢀaminophenyl)ꢀ2ꢀmethyldiazene
1
13
8.4 Hz, J = 1.3 Hz). C NMR (acetoneꢀd ), δ: 12.8 (CH ); 47.6
6 3
5
ꢀoxide (1a), 1ꢀ(2ꢀaminophenyl)ꢀ2ꢀisopropyldiazene 1ꢀoxide
(CMe ); 116.6 (C(6)); 119.0 (C(4)); 125.5 (C(3)); 132.8 (C(5));
3
5
4
14
(
1c), 1ꢀ(2ꢀaminophenyl)ꢀ2ꢀ(tertꢀbutyl)diazene 1ꢀoxide (1d),
143.9 (C(1)). N NMR (acetoneꢀd ), δ: –46 (∆ν
= 80 Hz,
6
1/2
+
2
ꢀ(tertꢀbutylꢀNNOꢀazoxy)phenyldiazonium
tetrafluoroꢀ
N(O)=N); –324 (∆ν1/2 = 500 Hz, NH ). MS, m/z: 165 [M] .
2
3
borate (2d), 5ꢀbromoꢀ2ꢀ(tertꢀbutylꢀNNOꢀazoxy)phenyldiꢀ
azonium tetrafluoroborate (2e), 4ꢀbromoꢀ2ꢀ(tertꢀbutylꢀNNOꢀ
azoxy)phenyldiazonium tetrafluoroborate (2f),3 2ꢀ(tertꢀbutyl)ꢀ
Synthesis of diazonium tetrafluoroborates 2a—c (general proꢀ
3
cedure). A solution of azoxyaniline 1 (1.42 mmol) in dry CH CN
3
(5 mL) was added dropwise at –15 °C for 10 min to a stirred
1
4
1
ꢀ(2ꢀchloroꢀ5ꢀnitrophenyl)diazene 1ꢀoxide (5), 1ꢀ(2ꢀaminoꢀ
suspension of NOBF4 (180 mg, 1.56 mmol) in dry CH CN
3
1
3
phenyl)ꢀ2ꢀ(tertꢀbutyl)diazene (11a), , and 1ꢀ(2ꢀaminoꢀ5ꢀ
bromophenyl)ꢀ2ꢀ(tertꢀbutyl)diazene (11b).13
(8 mL). The reaction mixture was stirred at –15 °C for 15 min
and the solvent was removed by ~90% in vacuo at T ≤ 0 °C. The
2
ꢀEthylꢀ1ꢀ(2ꢀnitrophenyl)diazene 1ꢀoxide (4). Ethylamine
residue was diluted with cooled dry Et O. The precipitate of
2
hydrochloride (245 mg, 3 mmol) was added to a stirred solution
diazonium salt 2 was filtered off, washed with dry Et O and
2
of 1ꢀnitroꢀ2ꢀnitrosobenzene (410 mg, 2.7 mmol) in CH CN
pentane, and dried in vacuo at T ≤ 5 °C.
3
(
38 mL); then dibromoisocyanuric acid (900 mg, 3.3 mmol) was
2ꢀ(MethylꢀNNOꢀazoxy)phenyldiazonium tetrafluoroborate
(2a). Light yellow crystals, 95% yield, m.p. 98—100 °C
added. The reaction mixture was stirred at 24 °C for 5 h (moniꢀ
Table 5. 13C NMR spectra (75.5 MHz, CD Cl , δ, J/Hz) of benzotriazole 1ꢀoxides 6a—g
2
2
Comꢀ
pound
Alk
X
C(3a)
C(4)
C(5)
C(6)
C(7)
C(7a)
Alk
6
6
6
6
6
6
6
a
b
c
d
e
f
Me
Et
—
—
—
141.0
141.0
140.8
139.5
140.3
138.4
141.0
J = 5.9,
119.1
119.3
119.4
118.5
121.8
121.0
121.5
J = 175,
128.7
128.6
128.4
128.1
122.0
132.2
123.0
J = 171,
126.0
126.1
126.0
126.1
129.5
119.6
145.8
J = 4.1,
J = 5.9,
J = 10.8
113.8
113.8
113.8
113.4
115.3
116.4
112.7
J = 178,
131.4
131.3
131.2
127.6
126.8
128.8
127.1
J = 5.8
36.1
13.1, 44.7
20.9, 51.7
27.2, 66.7
27.0, 67.3
27.1, 67.3
26.7, 68.5
i
Pr
Bu
Bu
Bu
t
—
t
5ꢀBr
6ꢀBr
6ꢀNO2
t
t
g
Bu
2
1
1
2
2
1
2
3
2
2
3
J = 8.6
J = 3.9
J = 4.6,
J = 8.4,
3
3
4
J = 9.5
J = 1.5

1
018
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 4, April, 2005
Lipilin et al.
Table 6. 14N NMR spectra (21.7 MHz, CD Cl , δ) of benzoꢀ
triazole 1ꢀoxides 6a—g. Parenthetical values refer to ∆ν1/2/Hz
C H N O. Calculated (%): C, 47.46; H, 3.98; N, 39.53.
IR (KBr), ν/cm : 1490 (N→O); 2150 (N ). H NMR (CD Cl ),
3 2 2
2
2
7
7
5
–1
1
δ: 3.41 (s, 3 H, CH ); 7.21—7.27 (m, 2 H, Ar), 7.45—7.51 (m,
3
13
2
1
H, Ar). C NMR (CD Cl ), δ: 40.5 (CH ); 120.7 (C(3));
2 2 3
Compound
N(1)→O
N(2)—R
NO2
25.4 (C(6)); 125.6 (C(5)); 131.6 (C(4)); 133.6 (C(2)); 140.8
14
6
6
6
6
6
6
6
a
b
c
d
e
f
–70 (250)
–91 (150)
–91 (350)
–90 (300)
–89 (400)
–88 (350)
–82 (350)
–135 (600)
–120 (650)
–114 (850)
–116 (700)
–115 (800)
–139 (800)
–95 (850)
—
—
—
—
—
—
(C(1)). N NMR (CD Cl ), δ: –48 (∆ν = 90 Hz, N(O)=N);
–141 (∆ν1/2 = 80 Hz, —N=N=N).
1ꢀ(2ꢀAzidophenyl)ꢀ2ꢀethyldiazene 1ꢀoxide (3b). Dark yellow
oil, 78% yield. Found (%): C, 50.41; H, 4.70; N, 36.45.
C H N O. Calculated (%): C, 50.26; H, 4.74; N, 36.63.
IR (KBr), ν/cm : 1500 (N→O); 2170 (N ). H NMR (CD Cl ),
δ: 1.38 (t, 3 H, CH , J = 7.3 Hz); 3.65 (q, 2 H, CH , J = 7.3 Hz);
3 2
7
2 2 1/2
8
9
5
–1
1
3
2
2
g
—14 (130)
1
3
.18—7.28, 7.45—7.52 (both m, 2 H each, Ar). C NMR
(
decomp.). Found (%): C, 33.59; H, 2.79; N, 22.27.
(CD Cl ), δ: 12.2 (CH ); 47.9 (CH ); 120.6 (C(3)); 125.3 (C(6));
2
2
3
2
14
C H BF N O. Calculated (%): C, 33.64; H, 2.82; N, 22.41.
IR (KBr), ν/cm : 1500 (N→O); 2280 (N2+). H NMR (acꢀ
125.5 (C(5)); 131.3 (C(4)); 133.5 (C(2)); 140.9 (C(1)). N NMR
(CD Cl ), δ: –51 (∆ν = 60 Hz, N(O)=N); –142 (∆ν1/2
7
7
4
4
–
1
1
=
2
2
1/2
etoneꢀd ), δ: 3.61 (s, 3 H, CH ); 8.32 (ddd, 1 H, H(5), J =
50 Hz, —N=N=N).
6
3
8
8
.0 Hz, J = 7.8 Hz, J = 1.5 Hz); 8.55.(ddd, 1 H, H(4), J =
.1 Hz, J = 8.0 Hz, J = 1.3 Hz); 8.73 (dd, 1 H, H(3), J = 8.1 Hz,
1ꢀ(2ꢀAzidophenyl)ꢀ2ꢀisopropyldiazene 1ꢀoxide (3c). Brown
oil, 90% yield. Found (%): C, 52.83; H, 5.37; N, 33.95.
C H N O. Calculated (%): C, 52.67; H, 5.40; N, 34.13. IR
J = 1.5 Hz); 9.04 (dd, 1 H, H(6), J = 7.8 Hz, J = 1.3 Hz).
9
11
5
13
–1
1
C NMR (acetoneꢀd ), δ: 40.9 (CH ); 110.8 (C(1)); 127.0
(KBr), ν/cm : 1490 (N→O); 2130 (N ). H NMR (CD Cl ),
3 2 2
6
3
(
C(3)); 135.1 (C(5)); 137.8 (C(6)); 143.3 (C(3)); 145.7 (C(2)).
δ: 1.27 (d, 6 H, 2 CH , J = 6.7 Hz); 4.60 (h, 1 H, CHMe , J =
3 2
1
4
N NMR (acetoneꢀd ), δ: –61 (∆ν
= 60 Hz, N(O)=N);
1/2
6.7 Hz); 7.18—7.27, 7.44—7.49 (both m, 2 H each, Ar).
6
+
13
–
154 (∆ν1/2 = 160 Hz, N2 ).
C NMR (CD Cl ), δ: 19.5 (CH ); 52.4.0 (CHMe ); 120.6
2
2
3
2
2
ꢀ(EthylꢀNNOꢀazoxy)phenyldiazonium tetrafluoroborate (2b).
(C(3)); 125.1 (C(6)); 125.5 (C(5)); 131.2 (C(4)); 133.4 (C(2));
14
Light yellow crystals, 66% yield, m.p. 132—134 °C (decomp.).
141.5 (C(1)). N NMR (CD Cl ), δ: –53 (∆ν
= 50 Hz,
1/2
2
2
Found (%): C, 36.21; H, 3.45; N, 21.49. C H BF N O. Calcuꢀ
N(O)=N); –141 (∆ν1/2 = 50 Hz, —N=N=N).
8
9
4
4
–
1
lated (%): C, 36.40; H, 3.44; N, 21.22. IR (KBr), ν/cm : 1500
1ꢀ(2ꢀAzidophenyl)ꢀ2ꢀ(tertꢀbutyl)diazene 1ꢀoxide (3d). Dark
yellow oil, 85% yield. Found (%): C, 54.65; H, 5.94; N, 31.73.
C H N O. Calculated (%): C, 54.78; H, 5.98; N, 31.94.
1
(
N→O); 2300 (N2+). H NMR (acetoneꢀd ), δ: 1.47 (t, 3 H,
6
CH , J = 7.4 Hz); 4.86 (q, 2 H, CH , J = 7.4 Hz); 8.33 (ddd,
3
2
10 13
5
–1
1
1
H, H(5), J = 8.8 Hz, J = 8.1 Hz, J = 1.5 Hz); 8.58 (ddd, 1 H,
IR (KBr), ν/cm : 1480 (N→O), 2130 (N ). H NMR (CD Cl ),
3 2 2
t
H(4), J = 8.4 Hz, J = 8.1 Hz, J = 1.5 Hz); 8.78 (dd, 1 H, H(3),
J = 8.4 Hz, J = 1.5 Hz); 9.11 (dd, 1 H, H(6), J = 8.8 Hz, J =
δ: 1.44 (s, 9 H, Bu ); 7.25—7.35, 7.41—7.50 (both m, 2 H each,
13
Ar). C NMR (CD Cl ), δ: 25.8 (CH ); 60.2 (CMe ); 120.5
2
2
3
3
13
1
.5 Hz). C NMR (acetoneꢀd ), δ: 11.8 (CH ); 49.1 (CH CH );
(C(3)), 124.9 (C(6)), 125.4 (C(5)), 130.8 (C(4)), 133.2 (C(2)),
6
3
2
3
14
1
(
10.8 (C(1)); 127.1 (C(3)); 135.1 (C(5)); 137.3 (C(6)); 143.2
142.1 (C(1)). N NMR (CD Cl ), δ: –53.0 (∆ν
= 80 Hz,
2
2
1/2
C(4)); 145.8 (C(2)). 14N NMR (acetoneꢀd ), δ: –64 (∆ν
=
N(O)=N); –142 (∆ν
+
191 [M – N ] .
2
= 90 Hz, —N=N=N). MS, m/z:
1/2
6
+
1/2
8
0 Hz, N(O)=N); –154 (∆ν1/2 = 160 Hz, N2 ).
ꢀ(IsopropylꢀNNOꢀazoxy)phenyldiazonium tetrafluoroborate
2c). Colorless crystals, 79% yield, m.p. 112—114 °C (decomp.).
Found (%): C, 38.96; H, 3.98; N, 20.33. C H BF N O. Calcuꢀ
2
1ꢀ(2ꢀAzidoꢀ4ꢀbromophenyl)ꢀ2ꢀ(tertꢀbutyl)diazene 1ꢀoxide
(3e). Yellow crystals, 46% yield, m.p. 36—38 °C (decomp. at
68 °C). Found (%): C, 40.45; H, 4.11; Br, 26.98; N, 23.25.
C H BrN O. Calculated (%): C, 40.29; H, 4.06; Br, 26.80;
(
9
11
4
4
–
1
lated (%): C, 38.88; H, 3.99; N, 20.15. IR (KBr), ν/cm : 1500
1
0
12
5
N→O); 2300 (N2+). H NMR (acetoneꢀd ), δ: 1.37 (d, 6 H,
1
N, 23.49. IR (KBr), ν/cm : 1480 (N→O); 2120 (N ). H NMR
(CD Cl ), δ: 1.43 (s, 9 H, Bu ); 7.48 (dd, 1 H, H(5), J = 9.3 Hz,
–1
1
(
6
3
t
2
CH , J = 6.6 Hz); 4.46 (hept, 1 H, CHMe , J = 6.6 Hz); 8.29
3
2
2
2
(
1
ddd, 1 H, H(5), J = 8.4 Hz, J = 8.1 Hz, J = 1.5 Hz); 8.55 (ddd,
H, H(4), J = 8.4 Hz, J = 8.1 Hz, J = 1.4 Hz); 8.75 (dd, 1 H,
H(3), J = 8.4 Hz, J = 1.5 Hz); 9.05 (dd, 1 H, H(6), J = 8.1 Hz,
J = 1.3 Hz); 7.76 (d, 1 H, H(6), J = 9.3 Hz); 8.08 (d, 1 H, H(3),
13
J = 1.3 Hz). C NMR (CD Cl ), δ: 25.70 (CH ), 60.4 (CMe ),
2 2 3 3
123.6 (C(3)), 124.0 (C(4)), 126.2 (C(6)), 128.5 (C(5)), 134.8
1
3
14
J = 1.4 Hz). C NMR (acetoneꢀd ), δ: 19.3 (CH ); 54.2
(C(2)), 141.0 (C(1)). N NMR (CD Cl ), δ: –54 (∆ν
=
6
3
2
2
1/2
(
(
–
CHMe ); 110.9 (C(1)); 127.1 (C(3)); 135.0 (C(5)); 137.2
70 Hz, N(O)=N); –142 (∆ν1/2 = 150 Hz, —N=N=N).
2
14
C(6)); 143.2 (C(4)); 145.9 (C(2)). N NMR (acetoneꢀd ), δ:
1ꢀ(2ꢀAzidoꢀ5ꢀbromophenyl)ꢀ2ꢀ(tertꢀbutyl)diazene 1ꢀoxide
(3f). Yellow crystals, 70% yield, m.p. 72—76 °C (decomp.).
Found (%): C, 40.33; H, 4.09; Br, 26.69; N, 23.20.
C H BrN O. Calculated (%): C, 40.29; H, 4.06; Br, 26.80;
6
+
66 (∆ν1/2 = 80 Hz, N(O)=N); –154 (∆ν1/2 = 200 Hz, N2 ).
Synthesis of 2ꢀ(alkylꢀNNOꢀazoxy)ꢀ1ꢀazidobenzenes 3a—f
(
general procedure). Sodium azide (130 mg, 2.0 mmol) was added
at –10 °C to a stirred solution of diazonium tetrafluoroborate 2
0.5 mmol) in dry acetone (15 mL). The reaction mixture was
1
0
12
5
–
1
1
N, 23.49. IR (KBr), ν/cm : 1490 (N→O); 2140 (N ). H NMR
(CD Cl ), δ: 1.44 (s, 9 H, Bu ); 7.11 (d, 1 H, H(3), J = 8.6 Hz);
3
t
(
2
2
stirred at –10 °C for 30 to 60 min (monitoring by TLC) and
7.55 (dd, 1 H, H(4), J = 8.6 Hz, J = 2.1 Hz); 7.59 (d, 1 H, H(6),
13
poured into water. The product was extracted with CH Cl . The
J = 2.1 Hz). C NMR (CD Cl ), δ: 25.7 (CH ), 60.5 (CMe ),
2
2
2 2 3 3
extract was dried with MgSO4 and concentrated in vacuo at
T ≤ 20 °C. The residue was purified on a thin layer of silica gel
117.4 (C(5)), 122.1 (C(3)), 128.1 (C(6)), 132.6 (C(2)), 133.8
14
(C(4)), 142.3 (C(1)). N NMR (CD Cl ), δ: –55 (∆ν =
2
2
1/2
with CHCl as an eluent.
90 Hz, N(O)=N); –142 (∆ν1/2 = 80 Hz, —N=N=N).
3
1
ꢀ(2ꢀAzidophenyl)ꢀ2ꢀmethyldiazene 1ꢀoxide (3a). Dark yelꢀ
1ꢀ(2ꢀAzidoꢀ5ꢀnitrophenyl)ꢀ2ꢀ(tertꢀbutyl)diazene 1ꢀoxide (3g).
Sodium azide (130 mg, 2.0 mmol) was added at –10 °C to a
low oil, 60% yield. Found (%): C, 47.65; H, 3.93; N, 39.69.

2
ꢀAlkylbenzotriazole 1ꢀoxides
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 4, April, 2005
1019
stirred solution of chloro derivative 5 (50 mg, 0.194 mmol) in
DMF (5 mL). The reaction mixture was stirred at 20 °C for 4 h
silica gel with CHCl as an eluent to give compound 6d (103 mg,
3
95%) as light yellow crystals identical with an authentic sample.
Synthesis of 5ꢀbromobenzotriazole 1ꢀoxide 6e by oxidation of
4ꢀbromoꢀ2ꢀ(tertꢀbutylazo)aniline (11b) with perbenzoic acid. The
and poured into water. The product was extracted with CH Cl2
2
and the extract was dried with MgSO and concentrated in vacuo
4
at T ≤ 20 °C. The products were separated off by column chroꢀ
matography on silica gel with EtOAc—light petroleum (1 : 7) as
an eluent to give azide 3g (29 mg, 56%) and benzotriazole 1ꢀoxide
reaction of azoaniline 11b with PhCO H according to the above
procedure followed by column chromatography of the residue
3
on silica gel with CHCl —EtOAc (4 : 1) as an eluent gave
3
6
(
g (18 mg, 38%). Azide 3g: yellow crystals, m.p. 96—98 °C
decomp.). Found (%): C, 45.61; H, 4.54; N, 31.57.
C H N O . Calculated (%): C, 45.45; H, 4.58; N, 31.80.
5ꢀbromobenzotriazole 1ꢀoxide 6e in 49% yield. The product was
identical with an authentic sample.
Synthesis of benzotriazole 1ꢀoxide 6d without isolation of
intermediates. A solution of 1ꢀ(2ꢀaminophenyl)ꢀ2ꢀ(tertꢀbuꢀ
tyl)diazene 1ꢀoxide 1d (750 mg, 3.68 mmol) in dry MeCN
(13 mL) was added dropwise at –15 °C for 10 min to a stirred
1
0
12
6
3
–
1
IR (KBr), ν/cm : 1510 (N→O); 1380, 1520 (NO ); 2160 (N ).
2
3
1
t
H NMR (CD Cl ), δ: 1.43 (s, 9 H, Bu ); 7.38 (d, 1 H, J =
2
2
1
3
8
.5 Hz); 8.27—8.31 (m, 2 H, H(4) and H(6)). C NMR
(
CD Cl ), δ: 25.6 (CH ), 60.8 (CMe ), 121.1 (C(6)), 121.2
suspension of NOBF (480 mg, 4.0 mmol) in dry MeCN (19 mL).
2
2
3
3
4
(
C(3)), 125.9 (C(4)), 140.2 (C(2)), 140.9 (C(1)), 144.1 (C(5)).
The solution was stirred at –15 °C for an additional 15 min and
diluted with dry acetone (80 mL). Sodium azide (960 mg,
14.7 mmol) was added and the reaction mixture was stirred at
–10 °C for 1 h and poured into water. The product was extracted
14
N NMR (CD Cl ), δ: –16 (∆ν = 210 Hz, NO ), –57 (∆ν =
2
2
1/2
2
1/2
1
10 Hz, N(O)=N), 144 (∆ν1/2 = 130 Hz, —N=N=N).
Synthesis of 2ꢀalkylbenzotriazole 1ꢀoxides 6a—g (general proꢀ
cedure). A solution of 2ꢀ(alkylꢀNNOꢀazoxy)ꢀ1ꢀazidobenzene 3
1.0 mmol) in benzene (10 mL) was refluxed for a period of time
with benzene (3×15 mL), dried with MgSO , and refluxed for 4 h.
4
(
The solvent was removed in vacuo and the residue was chromatoꢀ
specified in Table 1. After the reaction was completed (monitorꢀ
ing by TLC), the solvent was removed in vacuo. When necesꢀ
sary, the product was purified on a thin layer of silica gel with
graphed on silica gel with CHCl as an eluent to give benzoꢀ
triazole 1ꢀoxide 6d (440 mg, 62%). The product was identical
with an authentic sample.
3
CHCl as an eluent.
Synthesis of 6ꢀnitrobenzotriazole 1ꢀoxide 6g without isolation
of intermediates. Sodium azide (81 mg, 1.24 mmol) was added to
a stirred solution of chloro derivative 5 (32 mg, 0.124 mmol) in
DMF (6 mL). The reaction mixture was stirred at 60—65 °C for
1 h and poured into water. The product was extracted with
CH Cl2 and dried with MgSO . The solvent was removed
3
2
ꢀMethylꢀ2Hꢀ1,2,3ꢀbenzotriazole 1ꢀoxide (6a). Light yelꢀ
low crystals, 85% yield. Found (%): C, 56.52; H, 4.74; N, 28.32.
C H N O. Calculated (%): C, 56.37; H, 4.73; N, 28.17. MS,
7
7
3
+
m/z: 149 [M] .
2
ꢀEthylꢀ2Hꢀ1,2,3ꢀbenzotriazole 1ꢀoxide (6b). Light yellow
2
4
crystals, 93% yield. Found (%): C, 59.03; H, 5.54; N, 25.59.
C H N O. Calculated (%): C, 58.88; H, 5.56; N, 25.75. MS,
m/z: 163 [M] .
in vacuo and the residue was chromatographed on silica gel with
CHCl as an eluent to give benzotriazole 1ꢀoxide 6g (27 mg,
8
9
3
3
+
92%). The product was identical with an authentic sample.
2
ꢀIsopropylꢀ2Hꢀ1,2,3ꢀbenzotriazole 1ꢀoxide (6c). Light yelꢀ
low crystals, 90% yield. Found (%): C, 60.88; H, 6.24; N, 23.89.
C H N O. Calculated (%): C, 61.00; H, 6.26; N, 23.71. MS,
Kinetic experiments
9
11
3
+
m/z: 177 [M] .
ꢀ(tertꢀButyl)ꢀ2Hꢀ1,2,3ꢀbenzotriazole 1ꢀoxide (6d). Light
Comparison of the decomposition rates of 2ꢀazidoꢀ1ꢀnitrobenꢀ
zene (7) and 2ꢀazidoꢀ1ꢀ(tertꢀbutylꢀNNOꢀazoxy)benzene (3d).
A mixture of compound 3d (100.4 mg, 0.467 mmol) and 2ꢀazidoꢀ
2
+
yellow crystals, 95% yield. MS, m/z: 191 [M] .
ꢀBromoꢀ2ꢀ(tertꢀbutyl)ꢀ2Hꢀ1,2,3ꢀbenzotriazole 1ꢀoxide (6e).
Colorless crystals, 95% yield. Found (%): C, 44.59; H, 4.47;
Br, 29.71; N, 15.38. C H BrN O. Calculated (%): C, 44.46;
5
1
ꢀnitrobenzene 7 (74.72 mg, 0.467 mmol) was dissolved in a
mixture of C H (2 mL) and C H CD (0.6 mL). The resulting
6
6
6
5
3
10
12
3
solution was transferred to a tube and the tube was placed in a
thermostat (T = 80 °C). Five samples were withdrawn from the
reaction mixture at 20ꢀmin intervals and their N NMR spectra
were recorded. Using the integral intensities of the signals for
the nitro group of 2ꢀazidoꢀ1ꢀnitrobenzene (7) (δ –13) and for
the azoxy group of compound 3d (δ –48), we plotted a linear
relationship between the concentration changes of the starting
reagents according to the general equation:8
+
H, 4.48; Br, 29.58; N, 15.56. MS, m/z: 269 [M] .
ꢀBromoꢀ2ꢀ(tertꢀbutyl)ꢀ2Hꢀ1,2,3ꢀbenzotriazole 1ꢀoxide (6f).
6
14
Light yellow crystals, 95% yield. Found (%): C, 44.33; H, 4.45;
Br, 29.79; N, 15.47. C H BrN O. Calculated (%): C, 44.46;
1
0
12
3
+
H, 4.48; Br, 29.58; N, 15.56. MS, m/z: 269 [M] .
ꢀ(tertꢀButyl)ꢀ6ꢀnitroꢀ2Hꢀ1,2,3ꢀbenzotriazole 1ꢀoxide (6g).
2
Bright yellow crystals, 90% yield. Found (%): C, 51.06; H, 5.11;
N, 23.95. C H N O . Calculated (%): C, 50.84; H, 5.12;
1
0
12
4
3
+
N, 23.72. MS, m/z: 236 [M] .
,
Synthesis of benzotriazole 1ꢀoxide 6d by oxidation of
2
ꢀ(tertꢀbutylazo)aniline (11a) with perbenzoic acid. A solution of
azoaniline 11a (100 mg, 0.565 mmol) in CH Cl (3 mL) was
where ν (c – c ) is the concentration of product j, ν (c – ck,0)
2
2
j
j
j,0
k
k
added dropwise at 0 °C to a solution of perbenzoic acid (250 mg,
is the concentration of product k, k is the reaction rate constant
j
1
4
.81 mmol) in Et O (12 mL). The reaction mixture was kept at
°C for 16 h. The excess of perbenzoic acid was removed by
for compound j, and k is the reaction rate constant for comꢀ
pound k.
2
k
treatment with 20% aqueous KI (5 mL). Then 20% aqueous
Na S O (5 mL) was added. The organic phase was separated,
washed with concentrated aqueous NaHCO3 (5×10 mL) and
Leastꢀsquares determination of the ratio of the cyclization
rate constants of compounds 3d and 7 gave 1 : 1.4±0.08.
Determination of the reaction order and the decomposition
rate constant of 2ꢀazidoꢀ1ꢀ(methylꢀNNOꢀazoxy)benzene (3a).
A solution of compound 3a (46 mg, 0.26 mmol) in C H (3 mL)
2
2
3
brine (2×10 mL), and dried with CaCl . The solvent was reꢀ
2
moved in vacuo and the residue was purified on a thin layer of
6
6

1020
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 4, April, 2005
Lipilin et al.
was placed in a thermostat (T = 80 °C). Seven samples were
withdrawn at 30ꢀmin intervals. The solvent was removed in vacuo
at a bath temperature no higher than 20 °C. The sample concenꢀ
trations of compound 3a were determined from the integral
intensities of the signal for the methyl group (δ 3.41) in the
4. A. M. Churakov, O. Yu. Smirnov, S. L. Ioffe, Yu. A.
Strelenko, and V. A. Tartakovsky, Izv. Akad. Nauk, Ser.
Khim., 1994, 1620 [Russ. Chem. Bull., 1994, 43, 1532 (Engl.
Transl.)].
5. D. L. Lipilin, A. M. Churakov, Yu. A. Strelenko, and V. A.
Tartakovsky, Izv. Akad. Nauk, Ser. Khim., 2002, 295 [Russ.
Chem. Bull., Int. Ed., 2002, 51, 311].
1
H NMR spectra with consideration of the integral intensity of
the signal for the methyl group in the final product 6a (δ 4.22).
An analogous experiment was carried out for the same initial
concentration of compound 3a (C = 0.875 mmol mL– ), while
withdrawing three samples at 1ꢀh intervals. Using the integral
substitution method,1 we found this reaction to obey the firstꢀ
order kinetics. The rate constant of this reaction with a standard
6. F. T. Boyle and R. A. Y. Jones, J. Chem. Soc., Perkin Trans. 2,
1973, 160.
1
7. E. T. Apasov, A. M. Churakov, Y. A. Strelenko, S. L. Ioffe,
and V. A. Tartakovsky, Tetrahedron, 1995, 51, 6775.
8. N. N. Lebedev, M. N. Manakov, and V. F. Shvets, Teoriya
khimicheskikh protsessov organicheskogo i neftekhimicheskogo
sinteza [A Theory of Chemical Processes in Organic and Petroꢀ
chemical Synthesis], Khimiya, Moscow, 1984, 375 pp. (in
Russian).
5
4
–1
deviation (10 •k = 0.65±0.04 s ) was obtained by statistical
processing of the constants (determined from the equation
kt = ln(C /C) for different C and C values) with consideration
0
0
1
6
of the tꢀtest value.
Determination of the decomposition rate constants of azides
9. Comprehensive Heterocyclic Chemistry, Vol. 5, Eds A. R.
Katritzky and C. W. Rees, Pergamon Press, New York,
1984, p. 669.
10. A. Boido, I. Vazzano, F. Sparatore, B. Cappelo, V. Diurno,
C. Matera, R. Marrazzo, S. Russo, M. L. Cenicola, and
E. Marno, Farmaco, 1989, 44, 257.
–
1
3
b—d,g. A solution of an azide in C H (C = 0.1 mmol mL )
6 6
was placed in a thermostat (T = 80 °C). Six samples were withꢀ
drawn at equal intervals (45 min for 3b, 30 min for 3c,d, and
min for 3g). The current azide concentrations were deterꢀ
5
mined from the integral intensities of signals for the alkyl groups
1
in the H NMR spectra as described above, which were used to
11. H. W. Heine, P. G. Williard, and T. R. Hoye, J. Org. Chem.,
1972, 37, 2980.
calculate the decomposition rate constants.
1
2. D. W. S. Latham, O. MethꢀCohn, and H. Suschitzky,
J. Chem. Soc., Perkin Trans. 1, 1977, 478.
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 04ꢀ03ꢀ
13. D. L. Lipilin, P. A. Belyakov, Y. A. Strelenko, A. M.
Churakov, O. Y. Smirnov, S. L. Ioffe, and V. A. Tartakovsky,
Eur. J. Org. Chem., 2002, 3821.
3
2432).
1
1
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4. A. E. Frumkin, A. M. Churakov, Yu. A. Strelenko, and V. A.
Tartakovsky, Izv. Akad. Nauk, Ser. Khim., 2000, 480 [Russ.
Chem. Bull., Int. Ed., 2000, 49, 482].
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Received November 1, 2004;
in revised form January 27, 2005