Products of 6-azidoquinoline photooxidation: Thermal and photochemical routes of nitroso oxide consumption

Full text of DOI:10.1134/S0012500812020036

ISSN 0012ꢀ5008, Doklady Chemistry, 2012, Vol. 442, Part 2, pp. 30–33. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © E.M. Chainikova, R.L. Safiullin, A.N. Teregulova, L.V. Spirikhin, E.G. Galkin, 2012, published in Doklady Akademii Nauk, 2012, Vol. 442, No. 4,
pp. 493–496.
CHEMISTRY
Products of 6ꢀAzidoquinoline Photooxidation:
Thermal and Photochemical Routes
of Nitroso Oxide Consumption
E. M. Chainikova, R. L. Safiullin,
A. N. Teregulova, L. V. Spirikhin, and E. G. Galkin
Presented by Academician M.S. Yunusov July 25, 2011
Received August 18, 2011
DOI: 10.1134/S0012500812020036
The photolysis of aryl azides in the presence of oxyꢀ three products (Fig. 1). The preparative separation of
gen leads to the corresponding nitro and nitroso comꢀ
pounds [1, 2]. These products are considered to result
from nitroso oxides (ArNOO), intermediate species
formed in the reaction of molecular oxygen with tripꢀ
let aromatic nitrenes [3].
the mixture resulted in isolation of ~5 mg of product
3
4
(peak
(peak
1
on the chromatogram), ~1 mg of product
2), and trace amounts of product (peak ).
5
3
Product
3
is a green crystalline solid with a melting
In this work, we have studied the products of phoꢀ
point of 200–202 , whose UV spectrum in acetoniꢀ
trile shows two strong absorption bands at 300 and
416 nm and a very weak band at 677 nm.
°
C
tooxidation of 6ꢀazidoquinoline
showed that there are two reaction channels of conꢀ
sumption of nitroso oxide : thermal and photochemꢀ
1 in acetonitrile and
2
ical. The major thermal channel is the isomerization
of the nitroso oxide with the opening of the aromatic
ring, while the minor photochemical channel leads to
formation of 6ꢀnitroquinoline.
NMR spectra in CD3CN (99.95% D) were
recorded on a Bruker AVꢀ500 spectrometer with TMS
as a reference. The 1H NMR spectrum of a solution of
product
3
indicates that
3 is a mixture of two comꢀ
pounds, 3а and
3b, in a 1 : 2 ratio. The spectrum of the
N3
OON
second compound is slightly shifted downfield relative
to that of the first one, the number of protons in the
first compound being exactly one half of that in the
N
N
1
2
1
second one. As a whole, the H NMR spectra of the
A solution of azide
trile (75 mL) saturated with oxygen was photolyzed
using filtered light (BSꢀ4 light filter, > 300 nm) of a
xenon lamp in a thermostated reactor at 20 . The
reaction was conducted until complete consumption
of the azide. The reaction mixture was analyzed by
reversedꢀphase HPLC (acetonitrile as a mobile
phase). The chromatogram indicated the formation of
1 (1 ×
10–3 mol/L) in acetoniꢀ
two compounds are very similar. This also holds true
for the 13C NMR spectrum. The intensity ratio for
matched signals is about 1 : 2, that is, the number of
carbon atoms in the first compound is half the number
in the second compound. This allows us to draw a conꢀ
λ
°
C
clusion that product
monomeric forms.
3 exists in solution in dimeric and
From the analysis of the spectral data, we conꢀ
cluded that compound is 3ꢀnitrosoindolizineꢀ8ꢀcarꢀ
baldehyde formed according to Scheme 1.
3
Institute of Organic Chemistry, Ufa Research Center, Russian
Academy of Sciences, pr. Oktyabrya 71, Ufa, 450054, Russia
30

PRODUCTS OF 6ꢀAZIDOQUINOLINE PHOTOOXIDATION
31
O O
3N
N3
O2
N
hν
–N2
N
O
N
N
1
2
O
–
7
O
O
O
10
+N
6
5
8
9
N
N4
1
N
N
3
2
O
N
3a
Scheme 1.
For monomer 3a 1H NMR (500 MHz, CD3CN,
ppm): 10.19 (1H, C(10)H, 10.01 (dd, 1H, C(5)H, 3J
7.1, 4
1.1), 7.47 (d, 1H, C(1)H, 5.1), 8.26 (dd, 1H,
C(7)H, 3
(t, 1H, C(6)H,
δ
,
The terminal oxygen atom of the nitroso oxide
group of compound reacts at the ortho position of
2
the aromatic ring to form a fiveꢀmembered ring.
The ring decomposes with cleavage of the C–O and
O–O bonds, and the aromatic ring transforms into
nitrile oxide, which is stabilized to form nitroso
compound 3а. It is known that nitroso compounds
can dimerize [4]:
J
J
J
7.1, 4
J
J
1.1), 6.86 (d, 1H, C(2)H,
7.1).
J 5.1), 7.45
Signal assignment in the 13C NMR spectrum of the
dimer: 192.03 (C(10), C(10')), 156.31 (C(3), C(3')),
140.00 (C(7), C(7')), 135.40 (C(1), C(1')), 131.68
(C(10), C(10')), 156.31 (C(3), C(3')), 140.00 (C(7),
C(7')), 135.40 (C(1), C(1')), 131.68 (C(5), C(5')),
128.25 (C(9), C(9')), 126.50 (C(8), C(8')), 120.45
(C(6), C(6')), 110.69 (C(2), C(2')). For the monomer
7'
O
7
O
6
6'
8
10'
5
10
5'
+
8'
9'
–
9
O
N4
4'N
+
1'
13C NMR (CD3CN,
, ppm): 191.87 (C(10)), 162.01
δ
1
N N
O– 3'
3
2'
2
(C(3)), 139.52 (C(7)), 109.70 (C(1)), 128.94 (C(5)),
135.84 (C(9)), 126.50 (C(8)), 117.36 (C(6)), 104.35
(C(2)).
3b
Thus, the signal assignment in the 1H NMR specꢀ
trum of dimer (500 MHz, CD3CN, , ppm): 10.23
(s, 2H, C(10)H, C(10')H), 10.17 (dd, 2H, C(5)H,
C(5')H, 3J 7.1, 4
1.1), 8.42 (d, 2H, C(1)H, C(1')H,
5.1), 8.27 (dd, 2H, C(7)H, C(7')H, 3 7.1, 4
1.1), 7.66
(d, 2H, C(2)H, C(2')H, 5.1), 7.48 (t, 2H, C(6)H,
C(6')H, 7.1).
The structure of compound
mass spectroscopy (TermoFinnigan MAT95XP). MS
(EI, 70 eV,
rel, %)): 174 [M]+ (100), 144 [M–
3 was confirmed by
3b
δ
m/z (I
J
J
NO]+ (32.5), 158 [M–O]+ (8.2), 130 [M–O–CO]+
(13.2), 116 [M–NO–CO]+ (36.1), 89 [M–NO–CO–
NCH]+ (25.6).
J
J
J
J
0.8
0.6
0.4
0.2
0
1
2
4
3
0
1
2
3
4
5
6
Time, min
3
Chromatogram of a reaction mixture obtained by the photolysis of a solution of 6ꢀazidoquinoline in acetonitrile (1
saturated with oxygen. Mobile phase is acetonitrile, detection wavelengths are 240 and 300 nm. , product
product , initial azide
×
2
10⎯ mol/L)
1
3;
, product
4; 3,
5;
4
1.
DOKLADY CHEMISTRY Vol. 442
Part 2
2012

32
CHAINIKOVA et al.
Table 1. The yield of products of photooxidation of 6ꢀaziꢀ
diating solutions of compound
acetonitrile saturated with oxygen by filtered light of a
xenon lamp using a BSꢀ4 light filter ( > 300 nm), an
UFSꢀ2 filter (270–380 nm), or their combination
(300–380 nm) until complete consumption of the
azide. The data of Table 1 show that the use of a narrow
wavelength range for irradiation leads to a decrease in
1 (~1 ×
10–4 mol/L) in
doquinoline in acetonitrile at 20
°C
λ
Yield, % *
Photolyticsource
wavelength
range, nm
[
1
]0,
mol/L
3
4
300–1000
270–380
1.07
×
×
×
×
×
10–4
70
84
86
95
87
14
4
1.09
1.03
1.06
1.08
10–4
10–4
10–4
10–4
the yield of 6ꢀnitroquinoline
yield of nitroso compound
mum of aromatic nitroso oxides is known to be, as a
rule, in the longꢀwavelength spectral region (λmax
4
and an increase in the
3. The absorption maxiꢀ
300–380
3
300–380
4
>
300–380
4
400 nm) [5]. Therefore, our results indicate the photoꢀ
chemical origin of formation of ArNO2 from ArNOO:
* Per consumed azide.
–
O
For C9H6N2O2 anal. calcd. (%): C, 62.07; H, 3.45;
N, 16.09. Found (%): C, 61.72; H, 3.12; N, 15.36.
+
N
OON
hν
O
Compound
4 corresponding to the peak 2 in the
N
N
HPLC chromatogram (figure) was identified by mass
spectrometry as 6ꢀnitroquinoline (CAS 613503), the
similarity index for the library and recorded spectra
was 93%. MS (EI, 70 eV,
(100), 144 [M–NO]+ (6), 128 [M–NO2]+ (82).
This reaction is likely to proceed through the formaꢀ
tion of cyclic isomer of nitroso oxide 2, dioxaziridine.
m/z (I
rel, %)): 174 [M]+
The isomerization of nitroso oxides with cleavage
of the aromatic ring (Scheme 1) proceeds under mild
thermal conditions and constitutes the main reaction
channel of consumption of these species.
–
O
+
N
5
8
4
10
9
3
2
6
7
O
N
The N–O sesquibond in the nitroso oxide moleꢀ
cule [6] causes their existence as cis and trans isomers.
1
4
Compound
9.09 (dd, 1H, C(2)H, 3J 4.2, 4J 1.5), 8.91 (d, 1H,
C(5)H, 4J 2.5), 8.53 (d, 1H, C(4)H,
8.3), 8.46 (dd,
1H, C(7)H, 3 9.3, 4
2.5), 8.21 (d, 1H, C(8)H, 9.3),
7.68 (dd, 1H, C(3)H, 4.2).
8.3, 4
We failed to identify compound
4
: 1H NMR (500 MHz, CD3CN,
δ
, ppm):
Ar N
Ar N
O
O O
J
O
cis
J
J
J
trans
J
J
5
(peak 3 in the
Only the cis isomer of the nitroso oxide can react at the
ortho position of the aromatic ring. The high yield of
HPLC chromatogram (figure) isolated in trace
amounts, only molecular ion of 298 was detected.
substance
3 (table) indicates that it is a product of
Thus, the major products of the photooxidation of
6ꢀazidoquinoline are 3ꢀnitrosoindolizineꢀ8ꢀcarbaldeꢀ
transformation of both isomeric forms. In this case,
the trans form has to isomerize first into the cis form
(Scheme 1), which undergoes further transformations
hyde (3) (isolated yield ~37% toward the consumed
azide) and 6ꢀnitroquinoline (4) (~7%).
to give finally product 3.
To elucidate the effect of wavelength of photolytic
source on the yield of products of azide photooxidaꢀ
1
In [7], the authors revealed that the photolysis of
tion, we performed a quantitative analysis of reaction
mixtures by HPLC without isolation of products
(table). In this case, there is no loss of reaction prodꢀ
ucts inevitable for preparative separation, and analysis
results more adequately reflect the mechanism of the
phenazines 6a and 6b in the presence of oxygen in
benzene produced nitroso compound
yields, respectively. To explain the formation of
authors suggested Scheme 2, which is similar to
7
in 57 and 42%
7, the
studied process. The reaction was carried out by irraꢀ Scheme 1.
DOKLADY CHEMISTRY Vol. 442
Part 2
2012

PRODUCTS OF 6ꢀAZIDOQUINOLINE PHOTOOXIDATION
33
R
R
R
N
N
R
N3
3N
NOO
hν
O2
O
N
O
O
O
N
N
C R
N
N
C R
ONC
7
ON
R = H (6a), OCH3 (6b)
Scheme 2.
The work [7] was unnoticed by the specialists who Foundation for Basic Research (project no. 09–03–
00411).
study nitroso oxides [3] and the corresponding nitroꢀ
and nitrosobenzenes are still believed to be the main
transformation products of these species. In the
present study, we confirmed the results obtained in [7]
and showed that the main route of consumption of
nitroso oxides is the thermal reaction channel that
implies the intramolecular reaction of the NOO group
with the ortho position of the aromatic ring as the first
stage. Nitrobenzene can form from nitroso oxide only
upon photoexcitation of the latter.
REFERENCES
1. Abramovitch, R.A. and Challand, S.R., J. Chem. Soc.
Chem. Commun., 1972, pp. 964–965.
2. Go, C.L. and Waddel, W.H., Org. Chem., 1983, vol. 48,
no. 17, pp. 2897–2900.
3. Gritsan, N.P., Usp. Khim., 2007, vol. 76, no. 12,
pp. 1218–1240.
4. Feuer, H., The Chemistry of the Nitro and Nitroso
Groups, New York: Wiley, 1970. Translated under the
title Khimiya nitroꢀ i nitrozogrupp, Moscow: Mir, 1972,
vol. 1.
ACKNOWLEDGMENTS
5. Chainikova, E.M., Khursan, S.L., and Safiullin, R.L.,
Kinet. Katal., 2006, vol. 47, no. 4, pp. 566–571.
This work was supported by the Russian Academy
of Sciences (the program of the Division of Chemistry
and Materials Science “Chemical Reaction Intermeꢀ
diates: Their Detection, Stabilization, and Determiꢀ
nation of Structural Parameters) and the Russian
6. DeKock, R.L., McGuire, M.J., Piecuch, P., et al.,
J. Phys. Chem. A, 2004, vol. 108, no. 15, pp. 2893–
2903.
7. Albini, A., Betinetti, G., and Minoli, G., Org. Chem.
1987, vol. 52, no. 7, pp. 1245–1251.
,
DOKLADY CHEMISTRY Vol. 442
Part 2
2012