Electrochemical Synthesis of O-Phthalimide Oximes from α-Azido Styrenes via Radical Sequence: Generation, Addition and Recombination of Imide-N-Oxyl and Iminyl Radicals with C?O/N?O Bonds Formation

Article abstract of DOI:10.1002/adsc.202000618

Electrochemically induced radical-initiated reaction of vinyl azides with N-hydroxyphthalimide resulting O-phthalimide oximes with challenging for organic chemistry N?O-N fragment has been discovered. The developed approach introduces in synthesis electrochemically generated O-centered imide-N-oxyl radicals as the coupling components. Sequential formation of C?O and N?O bonds was achieved via generation and selective addition of imide-N-oxyl radicals, followed by recombination with iminyl radicals. A wide range of O-phthalimide oximes was obtained with the yields up to 84percent. (Figure presented.).

Full text of DOI:10.1002/adsc.202000618

Title: Electrochemical Synthesis of <i>O</i>-Phthalimide Oximes from
Vinyl Azides <i>via</i> Radical Sequence: Generation, Addition
and Recombination of Imide-<i>N</i>-Oxyl and Iminyl Radicals
with C-O / N-O Bonds Formation
Authors: Stanislav Alekseevich Paveliev, Artem Igorevich Churakov,
Liliya Sayarovna Alimkhanova, Oleg Olegovich Segida,
Gennady Nikishin, and Alexander Terent'ev
This manuscript has been accepted after peer review and appears as an
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content of this Accepted Article.
To be cited as: Adv. Synth. Catal. 10.1002/adsc.202000618
Link to VoR: https://doi.org/10.1002/adsc.202000618

10.1002/adsc.202000618
Advanced Synthesis & Catalysis
FULL PAPER
DOI: 10.1002/adsc.202((will be filled in by the editorial staff))
Electrochemical Synthesis of O-Phthalimide Oximes from
α-Azido Styrenes via Radical Sequence: Generation, Addition
and Recombination of Imide-N-Oxyl and Iminyl Radicals with
C-O / N-O Bonds Formation
Stanislav A. Paveliev, Artem I. Churakov, Liliya S. Alimkhanova, Oleg O. Segida,
Gennady I. Nikishin, Alexander O. Terent’ev *
N. D. Zelinsky Institute of Organic Chemistry of the Russian Academy of Sciences, 47 Leninsky prosp., Moscow119991,
Russian Federation
E-mail: terentev@ioc.ac.ru
Phone: (+7)-9163854080
Received: ((will be filled in by the editorial staff))
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201######.((Please
delete if not appropriate))
Abstract.
Electrochemically
induced radical-initiated
reaction of vinyl azides with N-hydroxyphthalimide resulting
O-phthalimide oximes with challenging for organic chemistry
N-O-N fragment has been discovered. The developed
approach introduces in synthesis electrochemically generated
Keywords: electrosynthesis; vinylazides; N-oxyl radicals;
N-hydroxyphthalimide; O-phthalimide oximes; N-O bond
O-centered imide-N-oxyl
radicals as the coupling
components.Sequentialformation ofC-O and N-O bonds was
achieved via generation and selective addition of imide-N-
oxyl radicals, followed by recombination with iminyl radicals.
A wide range of O-phthalimide oximes was obtained with the
yields up to 84%.
processes of C-O coupling[15] and functionalization of
alkenes,[16] their use in electroorganic synthesis is
limited to reactions in which they act as mediators of
benzylic[17] and allylic[18] C-H functionalization, as
well as various oxidation processes.[19]
Reactions involving vinyl azides, in which various
radical species add to the terminal carbon atom of the
double C=C bond of vinyl azide with the release of N2
molecule, gain growing interest (Scheme 1).[20]
Introduction
Currently, electroorganic synthesis is witnessing a
renaissance, being one of the most actively developing
areas of modern organic chemistry.[1] Using an
electrochemical methodology, a number of approaches
to the synthesis of important natural compounds,[2 ]
industrial products,[3] and heterocyclic structures[4]
was created. Great attention is paid to the
electrochemical C-H functionalization,[5] oxidative
coupling[6] and difunctionalization of alkenes and
alkynes.[7] Such processes are often accompanied by
the formation of reactive radical speciesthat play a key
role in the formation of the desired structures.[8]
Electric current is extensively used as a convenient
tool for the direct or indirect generation of C-,[9] O-,[10]
N-[11] and S-centered[12] radicals.
Electrochemical reactions involving stabilized O-
centered N-oxyl radicals represent a challenging area
of electrosynthesis.[13] Generation of imide-N-oxyl
radicals as a result of anodic oxidation of N-
hydroxyimides and their selective reactions with
substrates remains problematic due to the low stability
of such radicals under electrochemical conditions and
their tendency to self-decomposition.[14] Although
imide-N-oxyl radicals are widespread in many
Scheme 1. Present work in the context of the radical
transformations involving vinyl azides and iminyl radicals.
1
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10.1002/adsc.202000618
Advanced Synthesis & Catalysis
Table 1. Optimization of O-phthalimide oxime 3a
As a rule, the outcome of such processes is
electrosynthesis from vinyl azide
1a and N-
formation of iminyl radical and its subsequent
[a]
hydroxyphthalimide 2.
transformations resulting enamines[21] or ketones,[22] as
well
as
intramolecular
cyclization[23]
or
homocoupling.[24] To the best of our knowledge there
are no examples of the selective intermolecular
addition reactions involving iminyl radicals.
In the present work, it was found that imide-N-oxyl
radicals,
anodically
generated
from
N-
hydroxyphthalimide selectively reactwith vinyl azides
resulting in the formation of O-substituted oximes with
N-O-N fragment (hereinafter «O-phthalimide
oximes»). The main feature of the work is the
formation of a new N-O bond through the
recombination of N-centered iminyl radicals and O-
centered N-oxyl radicals. Surprisingly, no products of
iminyl radical reduction or dimerization were
observed. The stability of N-O bond in the discovered
process was unforeseen due to its electrochemical
lability and a tendency to cathodic reduction.[25]
№
solvent base
(molar ratio
electrolyte
yield
of 3a
(%)[b]
mol/mol 2)
1
2
3
4
5
6
7
8
acetone pyridine (1.5)
acetone pyridine (1.5)
acetone pyridine (1.5)
acetone pyridine (1.5)
acetone pyridine (1.5)
acetone pyridine (1.5)
CH3CN pyridine (1.5)
LiClO4
n-Bu4NClO4 27
n.d.
n-Bu4NBF4
[LutH]ClO4
[LutH]BF4
[PyH]ClO4
[PyH]ClO4
[PyH]ClO4
[PyH]ClO4
[PyH]ClO4
[PyH]ClO4
[PyH]ClO4
[PyH]ClO4
30
62
60
65
47
50
51
19
It should be noted that the products of the
discovered reaction bear two fundamentally important
functionalities – analogue of oxime ether and N-
alkoxyphthalimide. Oxime ethers have attracted much
attention due to their biological activities and wide
variety of synthetic applications.[26] Oxime ethers
exhibit fungicidal,[27] insecticidal,[27] herbicidal,[28 ]
antibacterial,[29] anticonvulsive[30] and anticancer[31]
effects. They are used in organic synthesis, providing
valuable synthons to obtain a number of medicinal
heterocyclic compounds.[32] Recently, oxime ethers
have been extensively employed as the precursors of
iminyl radicals in the various processes of radical
oxidative coupling and cyclization.[33] On the other
THF[c]
DCM
DMF
MeOH
HFIP
pyridine (1.5)
pyridine (1.5)
pyridine (1.5)
pyridine (1.5)
pyridine (1.5)
9
10
11
12
13
n.d.
n.d.
62
acetone 2,6-lutidine
(1.5)
acetone 2,4,6-collidine
(1.5)
acetone DBU (1.5)
acetone Et3N (1.5)
acetone DABCO (1.5)
acetone DMAP (1.5)
14
[PyH]ClO4
61
15
16
17
18
19
[PyH]ClO4
[PyH]ClO4
[PyH]ClO4
[PyH]ClO4
59
58
28
19
85
(83)
64
35
80
82
63
n.d.
29
55
hand,
N-alkoxyphthalimides
are
becoming
increasingly common in various photocatalytic
transformations asthe precursorsof O-and C-centered
radicals.[34] With this in mind, the development of new
methods for the synthesis both of oxime ethers and N-
alkoxyphthalimides is an urgent task of modern
organic chemistry.
acetone pyridine (1.0) [PyH]ClO4
20
21
acetone pyridine (0.5)
acetone
[PyH]ClO4
[PyH]ClO4
[PyH]ClO4
[PyH]ClO4
[PyH]ClO4
[PyH]ClO4
[PyH]ClO4
[PyH]ClO4
-
22[d] acetone pyridine (1.0)
23[e] acetone pyridine (1.0)
24[f] acetone pyridine (1.0)
25[g] acetone pyridine (1.0)
26[h] acetone pyridine (1.0)
27[i] acetone pyridine (1.0)
Results and Discussion
One of the key points of the work is the preparative
generation of stable N-oxyl radicals based on the direct
anodic oxidation of N-hydroxy compounds. Unlike
traditional methods for generating such radical, this
approach is does not imply the use of toxic and
expensive oxidants.
We commenced our investigations with the
optimization of the model electrochemical reaction of
(1-azidovinyl)benzene 1a with N-hydroxyphthalimide
2, resulting O-phthalimide oxime 3a. The data
concerning the influence of the solvent nature, type of
supporting electrolyte, base and its molar ratio to N-
hydroxyphthalimide, amount of the passed electricity
and current density are summarized in Table 1. All the
reactions were carried out in a thermostatically
controlled undivided electrochemical cell at 15 °C in
an air atmosphere.
[a] Reaction conditions: 1a (0.5 mmol, 73 mg), 2 (1.0 mmol,
163 mg), base (0.5−1.5 mmol, 40−489 mg), electrolyte
(0.5 mmol, 90−171 mg), solvent (15.0 mL), undivided
cell, graphite plate anode (15 × 25 × 3 mm), platinum
plate cathode (15 × 25 × 0.1 mm), constant current
electrolysis with i = 60 mA (janode = 16 mA/cm2), F = 1.1
F/mol 2 (reaction time 29 min), 15 °C.
[b] Yield determined by 1H NMR. Isolated yields are given
in parentheses.n.d. – not detected.The bold line of entry
19 indicates the conditions as optimal.
[c] 0.5 mL of H2O added.
[d] 1.5 F/mol 2 of electricity passed (reaction time 40 min).
[e] Constant current i = 40 mA (janode = 10.7 mA/cm2).
[f]
Constant current i = 80 mA (janode = 21.3 mA/cm2).
[g] Without electricity.
[h] Pt plate anode (15 × 25 × 0.1 mm).
[i] Ni plate cathode (15 × 25 × 0.1 mm).
2
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10.1002/adsc.202000618
Advanced Synthesis & Catalysis
The nature of an electrolyte turned out to be the key
Underthe optimal conditions (Table 1, entry 19), we
showed the applicability of the discovered process on
a variety of vinyl azides 1 (Table 2).
factor influencing in the studied process (Table 1,
entries 1−6). The initial experiment in acetone using
pyridine as a base and LiClO4 as a supporting
electrolyte does not allow to obtain product 3a (Table
1, entry 1). We speculate that the negative result was
causedby the formation of an insoluble red precipitate,
apparently, a salt of N-hydroxyphthalimide, which
covered the electrodes surface and suppressed the
reaction.[35] Thus, we turned our attention to organic
electrolytes. Employing quaternary ammonium salts
(n-Bu4NClO4 and n-Bu4NBF4), we obtained product
3a with a yield of 27−30% (Table 1, entries 2 and 3).
Based on the data concerning successful
Table 2. Electrochemical synthesis of O-phthalimide
oximes 3a-o from vinyl azides 1a-o and N-
hydroxyphthalimide 2. [a,b]
electrochemical
generation
of
imide-N-oxyl
radicals[17b] we decided to examine 2,6-lutidinium salts
as a supporting electrolyte. To our delight, reaction
with [LutH]ClO4 and [LutH]BF4 resulted 3a with
considerably higher yield (Table 1, entries 4 and 5,
60−62%). Further screening revealed pyridinium
perchlorate ([PyH]ClO4) as the best electrolyte for the
process under study, providing 3a with a 65% yield
(Table 1, entry 6).
Entries 7−12 showed that acetone was an optimal
solvent. When carrying out the reaction in other polar
aprotic solvents such as CH3CN, THF and DCM, the
yield of product 3a did not exceed 51% (Table 1,
entries 7−9). Reaction in DMF (Table 1, entry 10)
resulted 3awith the yield of 19%. In the reactions with
MeOHand HFIP the formation of 3awasnot observed
(Table 1, entries 11 and 12).
The nature of a base and its amount significantly
affects the yield of target product 3a. Pyridine-type
bases, such as 2,6-lutidine and 2,4,6-collidine, as well
as DBU and Et3N showed slightly lower efficacy
compared to pyridine (Table 1, entries 13−16, yield of
3a 58−62%). DABCO and DMAP (Table 1, entries 17
and 18) turned out to be unsuitable for the process
under study; in these cases, the yield of 3a did not
exceed 28%. Thus, pyridine was chosen as an optimal
base, and then the influence of its amount on 3a yield
wasstudied. Usage equimolar amount of pyridine with
respectto N-hydroxyphthalimide 2 causeda noticeable
increase in the yield of O-phthalimide oxime 3a(Table
1, entry 19, 85%), while decrease in the amount of the
base to 0.5 equivalents or its absence diminished the
yield of the reaction product (Table 1, entries 20 and
21, yield 3a 35−64%).
The optimal amount of electricity to carry out the
reaction is 1.1 F/mol 2; in this case, the current
efficiency is 91%. Reaction with the larger amount of
electricity (F = 1.5 F/mol 2) led to a slight decrease in
the yield of 3a (Table 1, entry 22, 80%). Both
increasing and decreasing the current density reduced
the yield of 3a (Table 1, entries 23 and 24, 63−82%).
The target product was not obtained in the absence of
electricity (Table 1, entry 25).
When varying the materials of the electrodes, the
use of a platinum anode, as well as a nickel cathode,
drastically reduced the yield of the target product
(Table 1, entries 26 and 27, 29−55% yield).
[a] Reaction conditions:1a-o (0.5 mmol, 73−111 mg), 2 (1.0
mmol, 163 mg), pyridine (1.0 mmol, 79 mg), [pyH]ClO4
(0.5 mmol, 90 mg), acetone (15.0 mL), undivided cell,
graphite plate anode (15 × 25 × 3 mm), platinum plate
cathode (15 × 25 × 0.1 mm), constant current electrolysis
with i = 60 mA (janode = 16 mA/cm2), F = 1.1 F/mol 2,
15 °C, air atmosphere.
1
[b] Isolated yield. Stereoisomeric ratios determined by H
NMR are given in parentheses.
The reaction successfully proceeds with various
aryl-containing vinyl azides 1b-m bearing electron-
3
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10.1002/adsc.202000618
Advanced Synthesis & Catalysis
donating alkyl and methoxy-groups in para-, meta-, data for the phthalimide-N-oxyl radical generated
and ortho- positions (3b-d, 3i-m, yield 53-84%) as
well as electron-withdrawing (NO2, halogens, CF3)
substituents (3e-3h, yield 40-70%). β-Substituted
vinyl azide 1n also enter the studied transformation,
giving O-phthalimide oxime 3n (yield 54%). In the
reaction with 2-(1-azidovinyl)naphthalene 1o, product
3o was obtained with the yield of 42%.
chemically.[37]
The synthetic utility of the developed protocol was
demonstrated by the synthesis of product 3a on a gram
scale amount (Scheme 2).
0,8
0,6
0,4
0,2
0
Current
[mA]
Scheme 2. Gram scale synthesis ofO-phthalimide oxime 3a.
-0,2
-0,4
In the reaction of 5 mmol of vinyl azide 1a with 10
mmol of N-hydroxyphthalimide 2 we obtained 1.78 g
of target O-phthalimide oxime 3a that corresponds to
the yield of 81%.
Potential vs. Ag/AgNO3
[mV]
-800
-300
200
700
1200
To clarify the reaction mechanism, we carried out
series of experiments with radical scavengers, cyclic
voltammetry and EPR analysis (Scheme 3).
Electrochemical reaction under standard conditions
for the synthesis of O-phthalimide oximes (Table 1,
entry 19) in the presence of 2,2,6,6-tetramethyl-1-
piperidinoxyl (TEMPO), 1,1-diphenylethylene and
butylated hydroxytoluene (BHT) (Scheme 3a) led to a
significant decrease in the yield of product 3a, which
indicated radical nature of the discovered process.
According to the results of the CV experiments
(Scheme 3b), we conclude that vinyl azide 1a and
pyridine are electrochemically inert in the range of -
0.5–1.4 V vs. Ag/AgNO3 (curves b and c). On the
voltammogram of NHPI 2 solution (curve d), we
observe the weak peaks at 0.69 V and 0.58 V,
corresponding to the reversible oxidation of NHPI 2 to
phthalimide-N-oxyl radical. Addition of 1 equiv. of
pyridine to the NHPI 2 solution (curve e) led to a
significant increase of the oxidation and reduction
currents (peaks at 0.96 V and 0.40 V, respectively).[36]
In the presence of vinyl azide 1a, the peak of reduction
of phthalimide-N-oxyl radical disappeared (curve f),
which indicated its interaction with vinyl azide.
To further confirm the formation of the
334
334.5
335
335.5
336
336.5
337
Magnetic field [mT]
Scheme 3. Experiments on the confirmation of the reaction
mechanism.
Based on the results of the control experiments and
literature data on electrochemical generation of imide-
N-oxyl radicals from N-hydroxyimides and the
addition of radical species to vinyl azides, we
suggested the reaction mechanism of electrochemical
synthesis of O-phthalimide oxime 3a involving
transformation of vinyl azide 1a under the action of N-
hydroxyphthalimide 2 (Scheme 4).
phthalimide-N-oxyl
radical
in
the studied
electrochemical system, an in-situ EC-EPR
experiment was conducted (Scheme 3c). A solution of
Initially, deprotonation of N-hydroxyphthalimide 2
N-hydroxyphthalimide
2
and pyridine in n-
under the action of pyridine gives anion A, the anodic
Bu4NClO4/MeCN was electrolyzed inside an EPR
cavity of spectrometer and EPR spectrum was
recorded simultaneously. The parameters of the
observed signal, such as g-factor and hyperfine
coupling constant, are in agreement with the literature
oxidation of which leads to the formation of
38]
phthalimide-N-oxyl
radical
(PINO).[36,
Subsequently, PINO adds to the terminal carbon atom
of double C=C bond of vinyl azide 1a with the
elimination of N2 molecule and formation of iminyl
4
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10.1002/adsc.202000618
Advanced Synthesis & Catalysis
radical B.[20] At the last stage recombination of B and
PINO radicals occurs giving final product 3a.
gram quantities. The proposed approach opens up
great opportunities for the selective introduction of
valuable hydroxylamine fragment into various organic
molecules under electrochemical conditions.
Experimental Section
General Procedure for Optimization of O-Phthalimide
Oxime 3a Electrosynthesis (Experimental Procedure for
Table 1)
An undivided 25 mL two-neck jacketed cell was equipped
with reflux condenser,graphite anode (15 × 25 × 5 mm, S =
3.75 cm2) and a platinum plate cathode (15 × 25 × 5 mm, S
= 3.75 cm2), and connected to a DC regulated power supply.
A solution of(1-azidovinyl)benzene 1a (0.5 mmol, 145 mg),
N-hydroxyphthalimide
2 (1.0 mmol, 163 mg), base
(pyridine, 2,6-lutidine, 2,4,6-collidine, DMAP, DABCO,
DBU, Et3N or Cs2CO3, 0.5−1.5 mmol, 40−489 mg) and
supporting electrolyte ([LutH]ClO4, [LutH]BF4, [PyH]ClO4 ,
n-Bu4NClO4 or n-Bu4NBF4, 0.5 mmol, 90−171 mg,) in 15.0
mL of solvent (DCM, CH3CN, acetone,acetone with 0.5 mL
of H2O, MeOH, HFIP, THF with 0.5 mL of H2O or DMF)
was electrolyzed using constant current conditions (i = 60
mA, janode = 16 mA/cm2) at 15 °C under magnetic stirring.
After passing 1.1−1.5 F/mol 2 of electricity (reaction time
29−40 min), electrodes were washed with DCM (2 × 20.0
mL). The combined organic phases were concentrated under
reduced pressure using a rotary evaporator (15−20 mmHg),
bath temperature ca. 50-55 °C. The yield of product 3a was
determined by 1H NMR analysis of a crude mixture using p-
methoxyacetophenone as the internal standard.In the entry
19 product 3awas isolated by flash column chromatography
on silica gel using DCM/EtOAc mixture as eluent (with the
volume part of EtOAc gradually increased from 2% to 4%).
Typical Procedure for the Electrosynthesis of the O-
Phthalimide Oximes 3a−o (Experimental Procedure for
Table 2)
Scheme 4. Proposed mechanism for the electrochemical
synthesis of O-phthalimide oxime 3a from vinyl azide 1a
and N-hydroxyphthalimide 2.
An undivided 20 mL two-neck jacketed cell was equipped
with reflux condenser,graphite anode (15 × 25 × 5 mm, S =
3.75 cm2) and a platinum plate cathode (15 × 25 × 5 mm, S
= 3.75 cm2), and connected to a DC regulated power supply.
A solution of vinyl azide 1a−o (0.5 mmol, 73−114 mg), N-
hydroxyphthalimide 2 (1.0 mmol, 163 mg), pyridine (1.0
mmol, 79 mg) and [PyH]ClO4 (0.5 mmol, 90 mg,) in 15.0
mL of acetone was electrolyzed using constant current
conditions (i = 60 mA, janode = 16 mA/cm2) at 15 °C under
magnetic stirring. After passing 1.1 F/mol of electricity
(reaction time 29 min), electrodes were washed with DCM
(2 × 20 mL). The combined organic phases were
concentrated under reduced pressure using a rotary
evaporator (15−20 mmHg), bath temperature ca. 50-55 °C.
Products 3a-o were isolated by column chromatography on
silica gel using DCM/EtOAc mixture as eluent (with the
volume part of EtOAc gradually increased from 2% to 4%).
Conclusion
In conclusion, we disclosed the electrochemically
induced reaction between vinyl azides and N-
hydroxyphthalimide resulting O-phthalimide oximes
with N-O-N fragment. The reaction is implemented in
an undivided cell and produces the desired O-
phthalimide oximes in moderate to high yields. The
developed approach is applicable to a wide range of α-
azido styrenes and is tolerant to various electron-
withdrawing and donating groups. The radical route
commences with the anodic generation of stabilized
phthalimide-N-oxyl radicals, which coupled twice
with starting vinyl azide and intermediate iminyl
radical to form C-O and N-O bonds. Cyclic
voltammetry and EPRspectroscopy confirmed the key
role of imide-N-oxyl radicals in the developed process.
The finding of the work is the application of pyridine
as a base and pyridinium perchlorate as an electrolyte,
which facilitates the anodic generation of phthalimide-
N-oxyl radicals and simultaneously protects the N-O
fragment from cathodic reduction. The synthesis is
successfully scaled to obtain the target products in
Experimental Procedure for Scheme 3
Reaction of Vinyl Azide 1a with N-hydroxyphthalimide 2
in Standard Conditions in the Presence of Radical
Scavengers
An undivided 25 mL two-neck jacketed cell was equipped
with reflux condenser,graphite anode (15 × 25 × 5 mm, S =
3.75 cm2) and a platinum plate cathode (15 × 25 × 5 mm, S
= 3.75 cm2) (see figure S1b in Supporting Information), and
connected to a DC regulated power supply.A solution of (1-
azidovinyl)benzene 1a (0.5 mmol, 73 mg), N-
hydroxyphthalimide
2 (1.0 mmol, 163 mg), radical
scavenger – TEMPO, 1,1-diphenylethylene or BHT (1.0
mmol, 156-220 mg), pyridine (1.0 mmol, 79 mg) and
[PyH]ClO4 (0.5 mmol, 90 mg,) in 15.0 mL of acetone was
electrolyzed using constant current conditions (i = 60 mA,
5
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10.1002/adsc.202000618
Advanced Synthesis & Catalysis
janode = 16 mA/cm2) at 15 °C under magnetic stirring. After
passing 1.1 F per mol 2 of electricity (reaction time 29 min),
electrodes were washed with DCM (2 × 20 mL). The
combined organic phases were concentrated under reduced
pressure using a rotary evaporator (15-20 mmHg), bath
temperature ca. 50-55 °C. The yield of product 3a was
determined by 1H NMR spectroscopy using p-
methoxyacetophenone as the internal standard.
[4] Y. Jiang, K. Xu, C. Zeng, Chem. Rev. 2018, 118, 4485-
4540.
[5] a) M. D. Kärkäs, Chem. Soc. Rev. 2018, 47, 5786-5865;
b) Q.-L. Yang, P. Fang, T.-S. Mei, Chin. J. Chem. 2018,
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[6] a) S. Tang, Y. Liu, A. Lei, Chem 2018, 4, 27-45; b) Y.
Yu, Y. Yuan, H. Liu, M. He, M. Yang, P. Liu, B. Yu, X.
Dong, A. Lei, Chem. Commun. 2019, 55, 1809-1812; c)
H. Zhang,A.Lei, Synthesis 2019, 51,83-96; d) H. Wang,
X. Gao, Z. Lv, T. Abdelilah, A. Lei, Chem. Rev. 2019,
119, 6769-6787.
General Procedure for Cyclic Voltammetry
Cyclic voltammetry (CV) was implemented on an IPC-Pro
M
computer-assisted potentiostat manufactured by
«Econix» (scan rate error 1.0%; potential setting 0.25 mV;
scan rate 100 mV∙s-1). The experiments were performed in
a 10 mL five-neck glass conic electrochemical cell with a
water jacket for thermostatting. CV curves were recorded
using a three-electrode scheme. In a typical case, 5 mL of a
solution was utilized. The working electrode was a disc
glassy-carbon electrode (d = 3 mm). A platinum wire served
as an auxiliary electrode. An Ag/AgNO3 electrode was used
as the reference electrode and was linked to the solution by
a porous glass diaphragm. The solutions were kept under
thermally controlled conditions at 15±0.5 °С and deaerated
by bubbling argon. Electrochemical experiments were
performed under an argon atmosphere. The working
electrode was polished before recording each CV curve.
[7] a) H. Mei, Z. Yin, J. Liu, H. Sun, J. Han, Chin. J. Chem.
2019, 37, 292-301; b) G. M. Martins, B. Shirinfar, T.
Hardwick, N. Ahmed, ChemElectroChem 2019, 6,
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The EPR spectra were recorded on Adani SPINSCAN X
spectrometer in a X-band range (ν~9.43 GHz). The
magnetic field modulation frequency was 100 kHz with 100
μT modulation amplitude. A quartz glass capillary tube
(inner diameter 1.2 mm) was filled with a solution of N-
hydroxyphthalimide (0.25M), pyridine (0.5M) and n-
Bu4NBF4 (0.5M) in MeCN and equipped with a platinum
wire anode and AgCl coated silver wire cathode (both 0.8
mm diameter), so that the interelectrode space is located in
the working area of spectrometer. Wires were connected to
PalmSens EmStat3+ potentiostat as follows: platinum wire
− working electrode, silver wire − counter and reference
electrode. Constant potentialof1V was applied for 30 s,and
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Acknowledgements
This work was supported by the Russian Foundation for Basic
Research (project № 19-29-08027).
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FULL PAPER
Electrochemical Synthesis of O-Phthalimide
Oximes from α-Azido Styrenes via Radical
Sequence: Generation, Addition and
Recombination of Imide-N-Oxyl and Iminyl
Radicals with C-O / N-O Bonds Formation
Adv. Synth. Catal. Year, Volume, Page – Page
Stanislav A. Paveliev, Artem I. Churakov, Liliya S.
Alimkhanova, Oleg O. Segida, Gennady I.
Nikishin, Alexander O. Terent’ev*
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