Thermal intramolecular transformation of key intermediates in the photooxidation of para -allyl-substituted phenyl azide

Article abstract of DOI:10.1021/jp401038g

The electronic spectra, kinetic regularities, and the mechanism of decay of the cis and trans isomeric forms of 4-[(2E)-1-methylbut-2-en-1-yl]phenylnitroso oxide (2) were studied by flash photolysis and product analysis. The mechanism of the consumption o

Full text of DOI:10.1021/jp401038g

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Article
Thermal Intramolecular Transformations of Key Intermediates
in the Photooxidation of para-Allyl-Substituted Phenyl Azide
Ekaterina Mikhailovna Chainikova, Evgeniy Yu. Pankratyev, Aigul
N. Teregulova, Rail R. Gataullin, and Rustam Lutfullovich Safiullin
J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/jp401038g • Publication Date (Web): 08 Mar 2013
Downloaded from http://pubs.acs.org on March 11, 2013
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Thermal Intramolecular Transformation of Key
Intermediates in the Photooxidation of para-Allyl-
Substituted Phenyl Azide
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Ekaterina M. Chainikova,* Evgeniy Yu. Pankratyev, Aigul N. Teregulova, Rail R. Gataullin, Rustam L.
Safiullin
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Institute of Organic Chemistry, Ufa Scientific Center, the Russian Academy of Sciences, 71 prosp.
Oktyabrya, 450054 Ufa, Russian Federation.
AUTHOR EMAIL ADDRESS: kinetic@anrb.ru; evgeniy@pankratyev.com; intereg@anrb.ru;
gataullin@anrb.ru; safiullinrl@anrb.ru
RECEIVED DATE
CORRESPONDING AUTHOR FOOTNOTE: E-mail: kinetic@anrb.ru. Fax: 7 (347) 235 6066.
Telephone: 7 (347) 235 5496.
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Abstract. The electronic spectra, kinetic regularities and the mechanism of decay of the cis and trans
isomeric forms of 4-[(2E)-1-methylbut-2-en-1-yl]phenylnitroso oxide (2) were studied by flash photolysis
and product analysis. The mechanism of the consumption of this nitroso oxide is the same as the one
proposed earlier for 4-methoxyphenylnitroso oxide. The trans-2 isomer is converted into cis-2, which
undergoes cyclization to the substituted benzo[d][1,2,3]dioxazole 3. The reopening of dioxazole ring yields nitrile
oxide. 4. The final product (3,4-dimethyl-3a,4-dihydro-2,1-benzisoxazol-5(3H)-ylidene)acetaldehyde (5)
is formed by the intramolecular [3+2]-cycloaddition of the nitrile oxide group of 4 to the allylic double
bond. To support the proposed mechanism, the quantum chemical calculations have been employed.
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KEYWORDS: Nitroso oxides, Kinetics of decay, Flash photolysis, Mechanism, Nitrile oxides.
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Introduction
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During the photolysis of aromatic azides in aerated solutions, the reaction of triplet nitrenes with
molecular oxygen leads to reactive intermediates – nitroso oxides:1–4
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They have been known since 1971, when the formation of the corresponding nitroso oxide was registered
during 1,4-diazobenzene photolysis in aerated glassy matrices.5 Since then, several groups of researchers
have studied the properties these intermediates using experimental6–22 and theoretical methods.8,22–26
Structure and reactivity of nitroso oxides have been discussed in a number of reviews.1–4
Owing to the one-and-a-half order of the N–O bond,8,25 cis–trans isomerism is typical for nitroso
oxides:
Ar N
Ar N
O O
O
O
cis
trans
Isomers have been detected for 4-amino-6–8 and 4-nitrophenylnitroso oxides13 in matrices by UV- and
IR-spectroscopy. In our previous work,18 the electronic spectra and kinetic regularities of decay of the
isomeric forms of a number of arylnitroso oxides were studied by flash photolysis in solutions. The
isomeric forms of all the studied nitroso oxides were consumed by a first-order reaction.
Until recently, there has been a lack of clarity on the mechanism of decay of nitroso oxides. The
corresponding nitro- and nitrosobenzenes are always formed in small amounts during the photooxidation
of aromatic azides.17,27,28 They were thought to be the final products of nitroso oxide transformations.
Not long ago, using 4-methoxyphenyl azide as an example, we showed that a sequence of
transformations takes place during the photolysis of aromatic azides in the presence of oxygen (Scheme
1).29
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Scheme 1
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According to Scheme 1, the monomolecular decay reaction of the trans form of nitroso oxides is
isomerization into the cis form. The two-stage transformation of the cis form leads to the final product, a
conjugated diene with nitrile oxide and aldehyde groups at the termini of the molecule. To support a two-
step mechanism, the monomolecular rearrangement of cis-form of a number of arylnitroso oxides has been studied
computationally.30 It should be noted that these reactions of the consumption of isomeric forms of nitroso
oxides (Scheme 1) are thermal.29 The photochemical reaction of nitroso oxides is reported to result in the
formation of the corresponding nitro compounds.9,31
Nitrile oxides are important synthetic intermediates, and are usually unstable compounds.32,33 Nitrile
oxide formed from 4-methoxyphenylnitroso oxide (Scheme 1, R = CH3O) are stable enough that we were
able to accumulate it in an amount sufficient to be identified.29 An intramolecular [3+2]-cycloaddition
reaction is typical of nitrile oxides.34,35 When the substituent R in the aromatic ring of the azide (Scheme
1) contains a double bond, for example the allylic type, the intramolecular cyclization of the nitrile oxide
group to the olefinic fragment leading to the stable heterocycle will be added to the sequence of
transformations. In this case, the task of accumulation and identification of the final products of the
transformations of nitroso oxides is simplified and the verification of a proposed mechanism (Scheme 1)
for other nitroso oxides is facilitated.
In this paper, we report on the mechanism of photooxidation of 4-[(2E)-1-methylbut-2-en-1-yl]phenyl
azide (1). The kinetics of decay of the cis and trans isomers of nitroso oxide 2 were studied by flash
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photolysis in acetonitrile, benzene, and hexane. The products of the photolysis of azide 1 in the presence
of oxygen were isolated and identified. The quantum chemical modeling of the elementary reaction steps
were performed to determine the rate-limiting step.
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N3
NOO
CH3
CH3 CH3
CH3
1
2
Experimental Section
HPLC grade acetonitrile (Panreac) and hexane (Cryochrom) were used without further
purification. Benzene was purified as described in ref. 36. Triphenylphosphine was recrystallized from
ethanol.
NMR spectra were registered on a Bruker AM-300 MHz spectrometer in deuterated acetonitrile
(Acros Organics, degree of deuteration 99.95%) using TMS as the internal standard.
UV-vis spectra were registered on a Shimadzu UV-365 spectrometer.
HRMS analysis was performed on a ThermoFinnigan MAT95XP mass spectrometer (EI, 70 eV,
direct inlet).
HPLC analysis was carried out on an YL9100 liquid chromatograph equipped with a two-wave UV–
vis detector. The reverse-phase analytical column was a Wakosil II 5C18 RS 4.6  250 mm (SGE), the
mobile phase was acetonitrile, the flow rate of mobile phase was 1 mL min–1, and the column was
operated at room temperature. The detection wavelengths were 250 and 310 nm. A Luna 10u C18 10 
250 mm column (Phenomenex) was used for preparative separation of the reaction mixtures.
Kinetic Experiments. A flash photolysis system previously described19 was used for the kinetic
experiments. The photolytic source was an IFP 5000-2 lamp; the maximum pulse energy was 400 J at U
= 5 kV, С = 32 µF; 90% light energy was emitted in 50 µs. The detector is the photomultiplier tube
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with the Sb-Cs photocathode, which has a spectral response in the range of 250–650 nm. The time
response is determined by the time constant of the registration channel (10 s). The reactor was a quartz
cell with an optical path length l = 10 cm, inner diameter of ~1 cm and volume of ~8 mL. The flash
photolysis of 2.5  10–4 M azide 1 solutions saturated with oxygen was performed with filtered light
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(UFS-2 light filter; transmittance range,  = 270–380 nm).
Synthesis of 4-[(2E)-1-methylbut-2-en-1-yl]aniline. 4.2 g (45 mmol) of aniline, 3.2 g (47 mmol) of
piperylene, 1.5 g (11 mmol) of AlCl3, and 4 mL of hexane was placed into a 17 mL rotating stainless steel
autoclave. The autoclave was heated at 130C for 4 hours, and then cooled. The reaction mixture was
neutralized with a 30 NaOH solution in water. The organic layer was extracted with tert-buthyl-
methylether and dried over KOH. The solvent was evaporated; the residue was distilled under vacuum.
Amine was isolated by chromatographing the boiling fraction at 105-110C on an alumina column and
eluting with light petroleum (b.p. 40-65C). 4-[(2E)-1-Methylbut-2-en-1-yl]aniline was obtained as a
1
yellow liquid in a yield of 5.1 g (70). H NMR (500 MHz, CDCl3, , ppm, J, Hz): 6.88 (d, 2 H, J =
7.8); 6.63 (d, 2 H, J = 7.8); 5.61 (ddd, 1 H, J = 13.0, 7.0, 1.2); 5.46 (dq, 1 H, J = 13.0, 6.3); 3.53 (s, 2 H
(NH2)); 3.31 (q, 1 H, J = 7.0); 1.70 (d, 3 H, J = 6.3); 1.33 (d, 3 H, J = 7.0). 13C NMR (125 MHz, CDCl3,
, ppm): 142.5, 137.0, 136.7, 125.4, 122.9, 115.1, 41.5, 21.7, 17.9.
4-[(2E)-1-Methylbut-2-en-1-yl]phenyl azide (1) was synthesized from 4-[(2E)-1-methylbut-2-en-1-
yl]aniline via the procedure described in the literature for trans-1-(o-azidophenyl)-1-pentene.37 1 was
obtained as a yellow liquid. 1H NMR (500 MHz, CDCl3, , ppm, J, Hz): 7.20 (dd, 2 H, J = 8.5, 1.7); 6.95
(dd, 2 H, J = 8.5, 2.0); 5.40-5.62 (m, 2 H), 3.40 (q, 1 H, J = 7.0); 1.70 (d, 3 H, J = 6.1); 1.31 (d, 3 H, J =
7.0). 13C NMR (125 MHz, CDCl3, , ppm): 143.3, 137.5, 135.8, 128.5, 123.9, 118.9, 41.7, 21.4, 17.0.
Photooxidation of 4-[(2E)-1-methylbut-2-en-1-yl]phenyl azide (1). Azide 1 (6.5 mg, 0.035 mmol)
was dissolved in 35 mL of acetonirile and placed in a thermostatically controlled (20C) quartz reactor.
To saturate the solution with oxygen, O2 was bubbled through it for 5 min. The resulting solution was
further purged with oxygen and irradiated by means of a xenon lamp through BS-4 and UFS-2 filters
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(300–380 nm) until the starting material had disappeared. The reaction mixture was concentrated to
about 0.5 mL and separated chromatographically.
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(3,4-Dimethyl-3a,4-dihydro-2,1-benzisoxazol-5(3H)-ylidene)acetaldehyde (5) was isolated in an
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amount of 4.7 mg (70% per consumed azide). Spectral data for isomers of 5: 5a - H NMR (500 MHz,
CD3CN):  (ppm) = 10.06 (d, J = 7.9 Hz, 1H, CHO), 6.72 (d, J = 9.7 Hz, 1H, H(6)), 6.57 (d, J = 9.7
Hz, 1H, H(7)), 5.96 (d, J = 7.9 Hz, 1H, H(10)), 4.52 (m, 1H, H(3)), 3.95 (m, 1H, H(4)), 3.18 (dd, J =
13
12.6 Hz, J = 6.3 Hz, 1H, H(3a)), 1.46 (d, J = 6.3 Hz, 3H, H(8)), 1.12 (d, J = 6.9 Hz, 3H, H(9)). C
NMR (125 MHz, CD3CN): (ppm) = 192.01 (C(11)), 159.01 (C(7a)), 156.88 (C(5)), 136.35 (C(6)),
128.42 (C(7)), 123.96 (C(10)), 80.25 (C(3)), 54.42 (C(3a)), 30.40 (C(4)), 18.85 (C(8)), 16.53 (C(9)).
1
5b - H NMR (500 MHz, CD3CN):  (ppm) = 10.15 (d, J = 7.7, 1H, CHO), 7.46 (d, J = 9.9 Hz, 1H,
H(6)), 6.78 (d, J = 9.9 Hz, 1H, H(7)), 5.92 (d, J = 7.7 Hz, 1H, H(10)), 4.47 (m, 1H, H(3)), 3.20 (dd, J =
12.6 Hz, J = 6.3Hz, 1H, H(3a)), 2.97 (m, 1H, H(4)), 1.44 (d, J = 6.1 Hz, 3H, H(8)), 1.05 (d, J = 6.3 Hz,
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3H, H(9)). C NMR (125 MHz, CD3CN):  (ppm) = 191.90 (C(11)), 158.72 (C(7a)), 156.75 (C(5)),
128.97 (C(6)), 128.54 (C(7)), 123.75 (C(10)), 80.37 (C(3)), 54.60 (C3a)), 37.96 (C(4)), 18.72 (C(8)),
1
16.23 (C(9)). 5c - H NMR (500 MHz, CD3CN):  (ppm) = 10.20 (d, J = 7.5 Hz, 1H, CHO); 7.62 (d, J
= 10.0 Hz, 1H, H(6)), 6.76 (d, J = 10.0 Hz, 1H, H(7)), 5.91 (d, J = 7.5 Hz, 1H, H(10)), 4.34 (m, 1H,
H(3)), 2.75 (m, 1H, H(4)), 2.72 (dd, J = 12.0 Hz, J = 6.3Hz, 1H, H(3a)), 1.52 (d, J = 6.3 Hz, 3H, H(8)),
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1.20 (d, J = 6.9 Hz, 3H, H(9)). C NMR (125 MHz, CD3CN):  (ppm) = 191.88 (C(11)), 158.25
(C(7a)), 156.92 (C(5)), 131.96 (C(6)), 126.66 (C(7)), 123.52 (C(10)), 84.46 (C(3)), 56.41 (C(3a)),
39.87 (C(4)), 19.97 (C(8)), 14.95 (C(9)).
Computational Methods. Quantum-chemical calculations were performed with the program package
Gaussian 09.38
The trans isomers of nitroso oxides have a significant contribution of the diradical resonance form to
the electronic structure of the molecule. So, the B3LYP and G3MP2B3 methods used successfully to
study the reactions of the cis form30 are not suitable for the investigation of the trans–cis isomerization.
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The B3LYP method significantly overestimates the stability of singlet diradicals,39 which leads to an
underestimation of the trans → cis isomerization energy barrier.30 In the case of the composite method,
G3MP2B3, one of the stages of calculations is carried out at the MP2 level, which is not applicable for
diradical systems. As the cis isomers of nitroso oxides have mainly a zwitterionic nature, the
transformation of the cis form of nitroso oxide 2 can be investigated at the UB3LYP/6-311+G(d,p) and
G3MP2B3 levels of theory. Recently, it was shown for the non-substituted nitroso oxide HNOO that the
pure functionals mPWPW91 and OLYP satisfactorily describe the trans–cis isomerization of nitroso
oxides.30
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So, in this work, all transformations were studied at the G3MP2B3, UB3LYP/6-311+G(d,p),
UOLYP/6-311+G(d,p), and UmPWPW91/6-311+G(d,p) levels of theory (See Supporting Information,
Table S1, S2). The latter method showed the best agreement with the experimental activation energy of
the trans–cis isomerization and ortho-cyclization of the nitroso oxide 2 (Table 1). Therefore, we will
discuss the energy characteristics, obtained using the UmPWPW91/6-311+G(d,p) method.
The symmetry of the systems of  and  electrons of the initial guess wave function was not restricted
by the application of these methods with the exception of G3MP2B3. The UB3LYP/6-311+G(d,p)
calculation of trans-2 accompanied by a triplet contamination of the wavefunction (S2 = 0.42, 0.03
after annihilation of the triplet component). The UmPWPW91/6-311+G(d,p) calculation of transition
state TS(trans-2, cis-2) accompanied by the high spin contamination of the wavefunction (S2 = 1.02,
0.14 after annihilation of the high spin components; 1.02, 0.16 and 1.04, 0.31 by UOLYP/6-311+G(d,p)
and UB3LYP/6-311+G(d,p), respectively).
For each compound and for each of the selected methods, the optimization of the structure and the
vibrational frequency analysis were performed. The correspondence of the transition states to the
reagents and products was confirmed by scanning the intrinsic reaction coordinate. Thermodynamic
parameters and activation energies were calculated for T = 298.15 K.
The visualization of the results of the quantum-chemical calculations was performed with the program
ChemCraft 1.6.40
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Results and Discussion
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Kinetics of Decay and Electronic Spectra of the Isomeric Forms of Nitroso Oxide 2
Transient absorption, which decays within ~20 sec, was observed upon flash photolysis of azide 1
solutions in acetonitrile, benzene, and hexane in the presence of oxygen in the wavelength region of 360–
490 nm (Figure 1). In acetonitrile and benzene, the shape of the decay kinetic curves of transient
absorption depends on the observation wavelength. The kinetic curves registered in the long-wavelength
region ( > 440 nm) were described by a first-order equation (Figure 1, Curve 1):
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A  A  (A  A )ekt
,
(1)
0
where А0 and А are optical densities of the solution immediately after excitation and at the end of the
reaction, respectively.
The kinetic curves recorded at wavelengths from 360 to 440 nm were well-approximated by a
biexponential equation (2) (Figure 1, Curve 2). This means that the observed transient absorption
corresponds to the two intermediates, each of which decays by a first-order law.
I
II t
A  A  A0I ek t  A0II ek
(2)
I
II
where A0 , A0 , kI, kII are the initial optical densities and rate constants of unimolecular decay of the
former and latter intermediate, respectively; A is the final absorbance of the solution.
By equation (1) from the kinetic curves registered at the wavelengths of 450–490 nm, the rate constant
were obtained, which are equal to kII obtained using equation (2). Thus, we observed the consumption of
the two species. The more labile of them absorbs light in the wavelength range of 360–440 nm. The
absorption spectrum of second intermediate is in the 360–490 nm range.
The absorption spectra of the two species in acetonitrile and benzene were constructed from the initial
optical densities calculated by equations (1) and (2) (Figure 2). The absorption maximum of the more
reactive intermediate was ~390 nm in both solvents, and the less reactive had a maximum of ~425 nm in
acetonitrile and ~420 nm in benzene. Since transient absorption is absent in the mentioned wavelength
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region upon flash photolysis of deaerated solutions of azide 1, one can state that the observed species are
cis and trans isomers of nitroso oxide 2.
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According to theoretical calculations,8,25 the cis isomers of nitroso oxides absorb light in a shorter
wavelength range than the trans isomers. As a consequence, the more labile intermediate formed upon
flash photolysis of azide 1 solutions in the presence of oxygen was the cis form of nitroso oxide 2, while
the more stable one was the trans form.
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In hexane, the shape of the decay kinetic curves of transient absorption was independent of the
observation wavelength. These kinetic curves are described well by equation (1) at all wavelengths (360–
490 nm) (Figure 3, Curve 1). This indicates that in a given solvent, the two species are consumed with
similar rate constants. Recently, it was shown that isomeric forms of nitroso oxides exhibit different
reactivity toward organic substrates, in particular to triphenylphosphine.20 Generally, the trans isomer
reacts with the substrate, whereas the cis isomer is much less reactive. This feature of isomeric forms can
be used for their kinetic separation in cases where the decay rate constants of the two species are similar.
When flash photolysis of the azide 1 solution in hexane is performed in the presence of additives of
triphenylphosphine, the two-component kinetic curves of the transient absorption decay recorded in the
wavelength region of 360–430 nm are approximated well by equation (2) (Figure 3, Curve 2). The fast
part of the kinetic curves corresponds to the consumption of the trans isomer of nitroso oxide 2 by the
reaction with triphenylphosphine, while the slow part corresponds to the consumption of the cis isomer.
We calculated the initial optical densities of the two species by equation (2) and constructed their
absorption spectra in hexane (Figure 4). The absorption maxima were ~385 and ~410 nm for the cis and
trans isomers, respectively.
The rate constant of the decay of the isomers of nitroso oxide 2 at 295 K in acetonirile and benzene are
calculated by equations (1) and (2) and listed in Table 1. In hexane, the rate constant of the trans isomer
consumption was obtained by the treatment of the kinetic curves of transient absorption decay registered
at wavelengths  > 430 nm using equation (1) (Table 1). To determine the rate constant magnitude of the
cis isomer decay in hexane, the linear dependence of the effective rate constant of its consumption vs. the
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concentration of Ph3P was obtained. From its intercept, the rate constant of the cis isomer decay was
calculated (Table 1). The temperature dependences of isomer decay rate constants were studied in the
range of 278–338 K. These dependences are described well by the Arrhenius law. Table 1 lists the
magnitude of activation energy and pre-exponential factors of the decay of cis and trans isomers in
acetonitrile, benzene, and hexane. The activation energy of trans isomer decay was 3–8 kJ mol–1 higher
than that of the cis isomer. For both species, the activation energy in hexane was 10–12 kJ mol–1 lower
than that in acetonitrile and benzene. The ratio cis/trans rate constant was ~2 in hexane and increased to
~8 in benzene and to ~20 in acetonitrile (Table 1).
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Mechanism of Azide 1 Photooxidation: Product Analysis.
On the basis of the results obtained earlier for 4-methoxyphenylnitroso oxide as an example (Scheme
1)29 and taking into account the ability of nitrile oxides to undergo intramolecular cycloaddition to the
double bond,34,35 we expected that photooxidation of azide 1 would occur in accordance with Scheme 2.
Scheme 2
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The photolysis of the solution of azide 1 (1  10–3 M) in acetonitrile saturated with oxygen was
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performed using the filtered light of a xenon lamp ( = 300–380 nm) at 293 K. The wavelength range of
irradiation was chosen in such a way to minimize the possible photochemical reactions of nitroso oxide.
The progress of the reaction was monitored by reversed-phase HPLC (See Experimental Section).
Judging from the chromatogram of the reaction mixture (Figure 5), the photooxidation of azide 1 yields a
single product, which was isolated and analyzed. On the basis of the 1H NMR spectrum, we can conclude
that the obtained compound consists of three isomeric forms, since each signal group of this spectrum
contains three similar signals with an intensity ratio of ~1 : 1.7 : 2.9 (Figure 6). This is most clearly seen
in the area of signals of aldehyde protons where three doublets with chemical shifts of 10.06, 10.15, and
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10.20 ppm are observed. The C NMR spectrum contains eleven signal groups, each of which consists
of three signals corresponding to three isomeric forms of the same compound (Figure 7). The obtained
product was identified as (3,4-dimethyl-3a,4-dihydro-2,1-benzisoxazol-5(3H)-ylidene)acetaldehyde 5
(Scheme 2) (See Experimental Section). Benzisoxazole 5 is formed as a mixture of three isomers 5a, 5b,
and 5c with a percentage ratio of 52%, 30%, and 18%, respectively (Scheme 3).
Scheme 3
The parent azide was used as a racemic mixture, so the isomerism of compound 4 is caused by cis/
trans orientation of the methyl substituent at C(4). In addition, the isomers differ by the aldehyde group
position with respect to the double bond C(5)=C(10). In accordance with Scheme 2, the location of
substituents must be maintained during the formation of nitrile oxide 4 from the aromatic ring. In this
case, the formation of benzisoxazole 5 with the trans aldehyde group as in the isomers 5b and 5c should
be expected. However, the conformer 5a prevails in the mixture (52%), possibly due to trans–cis
isomerization of the nitrile oxide 4 by keto-enol tautomerism:
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The structure of compound 5 was confirmed by mass spectrometry. The mass spectrum was obtained
(EI, 70eV), m/z: 191 [M]+ (100%), 176 [M-CH3]+ (33.9%), 165 [M-C2H2]+ (4.6%), 162 [M-CHO]+
(10.0%), 149 [M-CHCHO]+ (20.0%), 147 [M-C2H4O]+ (49.8%), 132 [M-C2H5NO] (24.6%). The mass
of the molecular and fragmentation ions correspond to the proposed structure. From the high resolution
mass spectrum, the molecular mass of the compound 5 was found: 191.0932. For the empirical formula
C11H13NO2 it is calculated: 191.0941. The absorption maximum of benzisoxazole 5 in acetotonitrile was
313 nm ( = 1.55  104 M–1 cm–1).
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The yield of benzisoxazole 5 was ~70% per consumed azide. Since other products were not formed in
the course of the reaction under study, it can be concluded that the transformations of both isomeric
forms of nitroso oxide 2 led to the same product. So, the mechanism of decay of aromatic nitroso oxides
proposed recently (Scheme 1)29 is valid for nitroso oxide 2. The kinetic parameters obtained by flash
photolysis (Table 1) correspond to the isomerization of the trans nitroso oxide 2 into the cis isomer and
to the decay of the cis isomer via cyclization (Scheme 2). Thus, the monomolecular reactions of the
consumption of cis and trans isomers of nitroso oxide 2 are of a different nature. Therefore, the polarity
of the solvent has a different effect on the rate constant of the two reactions (Table 1).
Theoretical Investigations of the Elementary Reaction Steps.
The elementary steps of the transformation of the isomeric forms of nitroso oxide 2 into the final
product were investigated by quantum-chemical methods (for the choice of methods, see the
Experimental Section).
It was found that the enthalpy H of the cis form of nitroso oxide 2 was 6.0 kJ mol–1 lower than that of
the trans form (Table 2, Reaction 1). According to our preliminary calculations, the same regularity is
observed for other aromatic nitroso oxides. The molecule of the cis form of nitroso oxides is stabilized by
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specific interactions such as orbital overlap between the lone pair of the terminal O atom and the
antibonding σ-ortho-C–H orbital of the aromatic ring as well as the nσ(N) → σ*(O–O) interaction.
The transition state (TS) of the trans → cis isomerization of nitroso oxide 2 was localized. It is
characterized by the N–O-bond lengthened by 0.2 Å compared to that in the reagent and product as well
as the perpendicular orientation of the O–O bond with respect to the aromatic ring plane. In the TS, the
length of the O–O bond is slightly (0.01 – 0.04 Å) shorter than that in the molecules of the reagent and
product. The sole imaginary frequency (210i cm-1) corresponds to the rotation of the N–O bond and the
change in the C–N–O bond angle and, therefore, to the process of trans–cis isomerization.
The activation barrier (ΔH≠) of the trans → cis isomerization of nitroso oxide 2 was calculated to be
69.2 kJ mol–1 (Table 2, Reaction 1). This magnitude is in quite good agreement with the experimental
activation energy (64.0–73.7 kJ mol–1) (Table 1).
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As follows from the experimental data, in spite of the greater thermodynamic stability of the cis form of
nitroso oxide 2, this species is kinetically less stable than the trans form. This is due to the fact that the cis
form decays via the ortho-cyclization reaction (Scheme 2), the activation energy of which is lower than
that of trans–cis isomerization in all solvents (Table 1).
The transition state of the ortho-cyclization of the cis isomer of nitroso oxide 2 was localized (TS(cis-
2, 3)) (Figure 8). The activation barrier of this reaction was calculated to be 66.4 kJ mol–1 (Table 2,
Reaction 2). This magnitude agrees well with the activation energies of the decay reaction of the cis
isomer of nitroso oxide 2 obtained by flash photolysis (Table 1). Reaction 2 is thermodynamically
favored: the enthalpy change is -143.9 kJ mol–1.
We were unable to localize the dioxazole 3 at the UmPWPW91/6-311+G(d,p) level of theory: the
ortho-cyclization of nitroso oxide 2 leads immediately to the formation of the nitrile oxide 4 (Scheme 2).
But the investigations at the B3LYP/6-311+G(d,p) and G3MP2B3 levels of theory showed that the ring
opening of the cycle 3 is characterized by a negligible activation barrier of 7.6 kJ mol–1 (B3LYP/6-
311+G(d,p)) and 18.3 kJ mol–1 (G3MP2B3) (See Supporting Information, Table S2).
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The transition states of the intramolecular [3+2]-cyclization of nitrile oxide 4 resulted in the formation
of the isomers of benzisoxazole 5b and 5c (Schemes 2 and 3): TS(4, 5b) and TS(4, 5c) (Figure 8). The
activation barriers of these reactions were calculated as 35.0 kJ mol–1 (Table 2, Reaction 3) and 38.8 kJ
mol–1 (Table 2, Reaction 4). Reactions 3 and 4 are thermodynamically favored: the calculated enthalpy
change values are -149.1 and -149.2 kJ mol–1, respectively.
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As can be seen from Table 2, the activation barrier of the intramolecular [3+2]-cycloaddition of nitrile
oxide 4 to the double bond is lower than that of ortho-cyclization of the cis form of nitroso oxide 2 (66.4
kJ mol–1), i.e. the process of reaction product formation is limited by this step. The trans form of nitroso
oxide 2, ultimately, also transforms into product 5 and, in this case, the slowest step is trans-2 → cis-2
isomerization, as evidenced by the experimental results (Table 1). We cannot exclude the fact that this
isomerization may be reversible. If the reverse reaction takes place, it would influence the kinetic
regularities of the decay of trans isomer of nitroso oxide 2; however, this was not observed (Figure 1, the
kinetic curve registered at 480 nm). Consequently, the cis-2 → trans-2 conversion loses in competition
with the ortho-cyclization of cis-2.
Conclusion
On the basis of the obtained results, we can conclude that the mechanism of the decay of the isomeric
forms of nitroso oxide 2 is the same as that proposed earlier for 4-methoxyphenylnitroso oxide. The
consumption rate constant of the trans isomer of nitroso oxide 2 measured by flash photolysis is the rate
constant of its isomerization into the cis isomer. The consumption rate constant of the cis isomer is the
rate constant of the cyclization to dioxazole cycle. The activation energy magnitude of the conversion of
the trans isomer into the cis isomer of nitroso oxide is in the range of 64.0–73.7 kJ mol–1, depending on
the nature of the solvent. The activation energy of the consumption reaction of the cis isomer is 56–68.2
kJ mol–1. The isomerization of the cis form into the trans form has no appreciable effect on the observed
kinetic regularities of the decay of nitroso oxide 2. This means that the energy cost required for this
reaction is much greater than that required for the cyclyzation of cis-2. The final product of the
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transformations of both isomeric forms of nitroso oxide 2 is benzisoxazole 5. The nature of the rate-
limiting step of the process depends on the transformation of the species considered. If product 5 is
formed from the trans form of nitroso oxide, then the rate-limiting step is the isomerization trans-2 →
cis-2. In the case where the final product is formed from the cis form, the process is limited by the step of
its cyclization.
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Acknowledgments. This work was supported by the Russian Academy of Sciences (Department of
Chemistry and Material Sciences program “Chemical Reaction Intermediates: Their Detection,
Stabilization, and Determination of Structural Parameters”) and by the Russian Foundation for Basic
Research, project no. 13-03-00201.
Supporting Information Available: NMR spectra of the mixture of the isomers 5a, 5b, and 5c. Total
energies and thermodynamic parameters of compounds and transitions states calculated by quantum-
chemical methods. Thermodynamic and activation parameters of elementary steps of transformation of
nitroso oxide 2 into the final product 5 calculated by quantum-chemical methods and Cartesian
coordinates. This material is available free of charge via the Internet at http://pubs.acs.org .
References
(1) Gritsan, N. P.; Pritchina, E. A. The Mechanism of Photolysis of Aromatic Azides. Russ. Chem.
Rev. 1992, 61, 500–515.
(2) Gritsan, N. P. Study of Photochemical Transformations of Organic Azides by Matrix Isolation
Techniques and Quantum Chemistry. Russ. Chem. Rev. 2007, 76, 1139–1160.
(3) Sawwan, N.; Greer, A. Rather Exotic Types of Cyclic Peroxides: Heteroatom Dioxiranes. Chem.
Rev. 2007, 107, 3247–3285.
(4) Ishiguro, K.; Sawaki, Y. Structure and Reactivity of Amphoteric Oxygen Species. Bull. Soc. Jpn.
2000, 73, 535–552.
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1
2
3
4
5
6
7
8
(5) Brinen, J. S.; Singh, B. Electron Spin Resonance and Luminescence Studies of the Reaction of
Photochemically Generated Nitrenes with Oxygen. Phosphorescence of Nitrobenzenes. J. Am. Chem.
Soc. 1971, 93, 6623–6629.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(6) Pritchina; E. A., Gritsan, N. P. Mechanism of p-Azidoaniline Photolysis in the Presence of Oxygen.
J. Photochem. Photobiol. A. 1988, 43, 165–182.
(7) Gritsan, N. P.; Pritchina, E. A. Mechanism of Photochemical Transformation of Aromatic Azides.
J. Inf. Rec. Mater. 1989, 17, 391–404.
(8) Pritchina, E. A.; Gritsan, N. P.; Bally, T. Matrix Isolation and Computational Study of the
Photochemistry of p-Azidoaniline. Phys. Chem. Chem. Phys. 2006, 8, 719–727.
(9) Harder, T.; Wessig, P.; Bendig, J.; Stösser, R. Photochemical Reactions of Nitroso Oxides at Low
Temperatures: The First Experimental Evidence for Dioxaziridines. J. Am. Chem. Soc. 1999, 121, 6580–
6588.
(10) Sawaki, Y.; Ishikawa, S.; Iwamura, H. Reactivity of Nitroso Oxides. Oxygen Transfer As an
Electrophilic Peroxy Radical. J. Am. Chem. Soc. 1987, 109, 584–586.
(11) Ishikawa, S.; Tsuji, S.; Sawaki, Y. Structure and Reactivity of Nitroso Oxides. J. Am. Chem. Soc.
1991, 113, 4282–4288.
(12) Ishikawa, S.; Nojima, T.; Sawaki, Y. Reactivity of Nitroso Oxides: Effect of Polar Substituents
and Reaction Mechanism. J. Chem. Soc. Perkin Trans. 2. 1996, 127–132.
(13) Inui, H.; Irisawa, M.; Oishi, S. Reaction of (4-Nitorophenyl)nitrene with Molecular Oxygen in
Low-temperature Matrices: First IR Detection and Photochemistry of Aryl Nitroso Oxide. Chem. Lett.
2005, 34, 478–479.
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2
3
4
(14) Zelentsov, S. V.; Zelentsova, N. V.; Zhezlov, A. B; Oleinik, A. V. Photooxidation of Organic
5
6
Azides. High Energy Chem. 2000, 34, 164–171.
7
8
9
(15) Makareeva, E. N.; Lozovskaya, E. L.; Zelentsov, S. V. Chemiluminescence upon Photooxidation
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
of 4,4'-Diazidodiphenyl with Molecular Oxygen. High Energy Chem. 2001, 35, 177–180.
(16) Srinivasan, A.; Kebede, N.; Saavedra, J. E.; Nikolaitchik, A. V.; Brady, D.; Yourd, E.; Davies, K.
M.; Keefer, L.; Toscano, J. P. Chemistry of the Diazeniumdiolates. 3. Photoreactivity. J. Am. Chem. Soc.
2001, 123, 5465–5472.
(17) Safiullin, R. L.; Khursan, S. L.; Chainikova, E. M.; Danilov, V. T. Formation of Nitroso Oxides in
the Photolysis of Aromatic Azides: Analysis of Products; Reaction Kinetics and Mechanism. Kinet.
Catal. 2004, 45, 640–648.
(18) Chainikova, E. M.; Khursan, S. L.; Safiullin, R. L. Isomeric Forms of Arylnitroso Oxides:
Electronic Spectra and Reactivity. Kinet. Catal. 2006, 47, 549–554.
(19) Chainikova, E. M.; Safiullin, R. L., Faizrakhmanova, I. M., Galkin, E. G. Reactions of Arylnitroso
Oxides with Substituted Styrenes: Kinetics and Products. Kinet. Catal. 2009, 50, 174–175.
(20) Chainikova, E. M.; Safiullin, R. L. Reactivity of Arylnitroso Oxides to Triphenylphosphine. Kinet.
Catal. 2009, 50, 527–529.
(21) Laursen, S. L.; Grace, L. E.; DeKock, R. L.; Spronk, S. A. Reaction of NH (X) with Oxygen in a
Solid Xenon Matrix: Formation and Infrared Spectrum of Imine Peroxide, HNOO. J. Am. Chem. Soc.
1998, 120, 12583–12594.
(22) Ling, P.; Boldyrev, A. I.; Simons, J.; Wight, C. A. Laser Photolysis of Matrix-Isolated Methyl
Nitrate: Experimental and Theoretical Characterization of the Infrared Spectrum of Imine Peroxide
(HNOO). J. Am. Chem. Soc. 1998, 120, 12327–12333.
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5
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7
8
(23) DeKock, R. L.; McGuire, M. J.; Piecuch, P.; Allen, W. D.; Schafer, H. F.; Kowalski, K.;
Kucharski, S. A.; Musial, M.; Bonner, A. R.; Spronk, S. A. et al. The Electronic Structure and
Vibrational Spectrum of trans-HNOO. J. Phys. Chem. A 2004, 108, 2893–2903.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
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34
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40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(24) Zelentsov, S. V.; Zelentsova, N. V.; Shchepalov, A. A. Nitrene Adducts with Oxygen in the
Photooxidation Reactions of Organic Azides. High Energy Chem. 2002, 36, 326–332.
(25) Talipov, M. R.; Ryzhkov, A. B.; Khursan, S. L.; Safiullin, R. L. Theoretical investigation of the
electronic spectra of aromatic nitrosooxides with allowance for solvent effects. J. Struct. Chem. 2006,
47, 1051–1057.
(26) Talipov, M. R.; Khursan, S. L.; Safiullin, R. L. RRKM and Ab Initio Investigation of the NH (X)
Oxidation by Dioxygen. J. Phys. Chem. A 2009, 113, 6468–6476.
(27) Abramovitch, R. A.; Challand, S. R. Reaction of Triplet Aryl Nitrenes and Azides with Molecular
Oxygen. J. Chem. Soc. Chem. Commun. 1972, 964–965.
(28) Go, C. L.; Waddel, W. H. Evolution of Photooxidation Products upon Irradiation of Phenyl Azide
in the Presence of Molecular Oxygen. J. Org. Chem. 1983, 48, 2897–2900.
(29) Chainikova, E. M.; Safiullin, R. L.; Spirikhin, L. V.; Abdullin, M. F. A Revised Mechanism of
Thermal Decay of Arylnitroso Oxides. J. Phys. Chem. A. 2012, 116, 8142-8147.
(30) Talipov, M. R.; Khursan, S. L.; Safiullin, R. L. A New Intramolecular Transformation of Aromatic
Nitroso Oxides. Russ. J. Phys. Chem. A. 2012, 86, 292–301.
(31) Chainikova; E. M., Safiullin, R. L.; Teregulova, A. N.; Spirikhin, L. V.; Galkin, E. G. Products of
6-Azidoquinoline Photooxidation: Thermal and Photochemical Routes of Nitroso Oxide Consumption.
Dokady Chem. 2012, 442, 30–33.
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2
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4
(32) Nitrile Oxides, Nitrones, and Nitronates in Organic Synthesis: Novel Strategies in Synthesis.
5
6
Second Ed. Feuer, H., Ed., John Wiley & Sons, Inc.: Hoboken, 2008.
7
8
9
(33) Kotyatkina, A. I.; Zhabinsky, V. N.; Khripach, V. A. 1,3-Dipolar Cycloaddition Reactions of
Nitrile Oxides in the Synthesis of Natural Compounds and Their Analogues. Russ. Chem. Rev. 2001, 70,
641-653.
10
11
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13
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20
21
22
23
24
25
26
27
28
29
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47
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53
54
55
56
57
58
59
60
(34) Annuziata, R.; Cinquini, M.; Cozzi, F.; Gennari, C.; Raimondi, L. Stereoselectivity of
Intramolecular Nitrile Oxide Cycloadditions to Z and E Chiral Alkenes. J. Org. Chem. 1987, 52, 4674–
4681.
(35) Hassner, A.; Amarasekara, A. S.; Padwa, A.; Bullock, W. H. A Novel Method of Ring Formation
with Functionalized Angular Methyl Groups. Limitations and MM2 Calculations. Tetrahedron Lett.
1988, 29, 715–718.
(36) Weisberger, A.; Proskauer, E. S.; Riddik, J. A.; Toops, E. E. Organic Solvents: Physical
Properties and Methods of Purification; Interscience: New York, 1955.
(37) Sundberg, R. G.; Russell, H. F.; Ligon, W. V., Jr.; Lin, L.-S. The o-Styrylnitrene Route to 2-
Substituted Indoles. Pyrolysis of o-Azidostyrenes. J. Org. Chem. 1972, 37, 719–724.
(38) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.;
Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A. et al. Gaussian 09, Revision C. 01; Gaussian,
Inc.: Wallingford, CT, 2010.
(39) Cramer, C. J. Essentials of Computational Chemistry: Theories and Models, Second ed.; John
Wiley & Sons, Inc.: New York, 2004.
(40) Zhurko, G. A. http:// www.chemcraftprog.com.
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Table 1. Rate Constants (Т = 295 K) and Activation Parameters of Decay of Isomeric Forms of
Nitroso Oxide 2.
6
7
8
9
cis
trans
solvent
10
11
12
13
14
15
16
17
18
19
20
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25
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30
31
32
33
34
35
36
37
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40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
kcis (s–1)
log k0cis
Ea (kJ mol–1)
56 ± 3
ktrans (s–1)
log k0trans
10.6 ± 0.2
12.8 ± 0.2
12.0 ± 0.1
Ea (kJ mol–1)
64 ± 1
С6Н14
C6H6
0.52 ± 0.02
1.45 ± 0.09
2.75 ± 0.08
9.7 ± 0.5
11.3 ± 0.1
12.0 ± 0.2
0.25 ± 0.04
68.2 ± 0.7
66 ± 2
0.172 ± 0.006
0.133 ± 0.002
71.4 ± 0.9
73.7 ± 0.7
CH3CN
Table 2. Thermodynamic and Activation Parameters of Elementary Steps of Transformation of Nitroso
Oxide 2 into the Final Product 5 Calculated by UmPWPW91/6-311+G(d,p) Method; ΔS (J mol–1 K–1),
ΔH, ΔG (kJ mol–1).
no
1
reaction
ΔS°
ΔH°
ΔG°
ΔS≠
0.2
ΔH≠
69.2
ΔG≠
69.2
2.2
-6.0
-6.6
trans-2 → [TS] → cis-2
2
44.0
-143.9
-157.0
-22.0
66.4
73.0
cis-2 → [TS]→ [3] → 4
3
4
-77.0
-78.0
-149.1
-149.2
-126.1
-125.9
-47.2
-51.5
35.0
38.8
49.1
54.2
4 → [TS] → 5b
4 → [TS] → 5c
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Figure captions
5
6
7
Figure 1. Kinetic curves of absorbance decay of nitroso oxide 2 in acetonitrile solution registered at
8
9
wavelengths of 480 nm and 400 nm (Т = 295 K). Solid lines correspond to the theoretical description.
10
11
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60
Figure 2. Electronic absorption decay associated spectra of the cis and trans forms of nitroso oxide 2 in
acetonitrile. Т = 295 K.
Figure 3. Kinetic curves of absorbance decay of nitroso oxide 2 in hexane solution registered at
wavelength of 390 nm (Т = 295 K). (1) – in the absence of Ph3P; (2) – in the presence of Ph3P (1.2 × 10–
5 M). Solid lines correspond to theoretical description.
Figure 4. Electronic absorption decay associated spectra of the cis and trans forms of nitroso oxide 2 in
hexane obtained in the presence of Ph3P (1.2 × 10–5 M). Т = 295 K.
Figure 5. Chromatogram of the reaction mixture obtained by photolysis of an O2-saturated acetonitrile
solution of azide 1 (1  10–3 М). The mobile phase is acetonitrile, and the detection wavelengths were
250 and 310 nm. tR = 3.12 min (product), tR = 4.78 min (azide 1).
1
Figure 6. H NMR spectrum of the product of azide 1 photooxidation in CD3CN. TMS was used as the
internal standard.
13
Figure 7. C NMR spectra of the product of azide 1 photooxidation in CD3CN. TMS was used as the
internal standard.
Figure 8. Optimized structures corresponding to the stationary points on the potential energy surface
calculated using UmPWPW91/6-311+G(d,p).
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Figures
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5
6
7
8
9
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
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60
400 nm
480 nm
0
10
20
30
40
Time (s)
Figure 1.
0.5
0.4
0.3
0.2
0.1
0.0
trans
cis
340
360
380
400
420
440
460
480
500
Wavelength (nm)
Figure 2.
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Time (s)
4
5
6
7
8
9
0
2
4
6
8
0.25
0.20
0.15
0.10
0.05
0.00
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(1)
(2)
0
5
10
15
20
25
Time (s)
Figure 3.
0.14
0.12
0.10
0.08
0.06
0.04
0.02
trans
cis
360
380
400
420
440
Wavelength (nm)
Figure 4.
[mV]
[%]
500
400
300
200
100
0
80
60
40
20
0
0
2
4
6
8
10
[min.]
Time
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Figure 5.
5
6
7
8
9
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14
15
10.2
10.1
ppm
7.5
7.0
6.5
6.0
5.5
5.0
4.5
4.0
ppm
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3.3
3.2
3.1
3.0
2.9
2.8
2.7
ppm
2.0
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
ppm
Figure 6.
dept90
com
190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
ppm
Figure 7.
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trans-2
TS(trans-2, cis-2), ν = 210i
TS(cis-2, 4), ν = 364i
cis-2
4
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TS(4, 5b), ν = 326i
TS(4, 5c), ν = 334i
5b
5c
Figure 8.
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