Synthesis of 1,2-Dicyano-3-arylcycl[3.2.2]azines – First 1,2-Dicarbonitriles Based on Cyclazine Heterocycle

Article abstract of DOI:10.1002/ejoc.202000958

The first 1,2-dicarbonitriles have been prepared for cyclazine systems. In particular, a synthetic procedure to 1,2-dicyano-3-arylcycl[3.2.2]azines has been developed. Unexpected chlorination of 3-arylcycl[3.2.2]azine-1,2-dicarboxylic acid derivatives by thionyl chloride at 4-position was found, which according to theoretical considerations can proceed by the electrophilic (S_EAr) mechanism. The compounds are blue fluorophores in 450–480 nm region with quantum yields in toluene of ca. 30 % for non-chlorinated derivatives, which decrease to 3–4 % for chlorinated ones.

Full text of DOI:10.1002/ejoc.202000958

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Heterocycles | Very Important Paper |
Synthesis of 1,2-Dicyano-3-arylcycl[3.2.2]azines – First
1,2-Dicarbonitriles Based on Cyclazine Heterocycle
Andrei S. Starikov,*[a] Valery V. Kalashnikov,[a] Pavel A. Tarakanov,[a] Anton O. Simakov,[a]
Sergey V. Simonov,[b] Valery V. Tkachev,[a,c] Alexander V. Yarkov,[a] Vladimir P. Kazachenko,[a]
Alexander V. Chernyak,[c] Fedor E. Zhurkin,[d] Larisa G. Tomilova,[a,e] and
Victor E. Pushkarev*[a,e]
Abstract: The first 1,2-dicarbonitriles have been prepared for which according to theoretical considerations can proceed by
cyclazine systems. In particular, a synthetic procedure to 1,2- the electrophilic (SEAr) mechanism. The compounds are blue
dicyano-3-arylcycl[3.2.2]azines has been developed. Unex- fluorophores in 450–480 nm region with quantum yields in
pected chlorination of 3-arylcycl[3.2.2]azine-1,2-dicarboxylic toluene of ca. 30 % for non-chlorinated derivatives, which de-
acid derivatives by thionyl chloride at 4-position was found, crease to 3–4 % for chlorinated ones.
ceptor.[9,10] In addition, partially hydrogenated cycl[3.2.2]azine
Pyrrolo[2,1,5-cd]indolizines, trivially named by their discov-
derivatives, Myrmicarins, represent natural alkaloids;[11–13] fully
hydrogenated cycl[3.2.2]azine fragment has also been recently
found in natural product,[14] which exhibits neuroprotective ac-
tivity. Thus, compounds of the cycl[3.2.2]azine family combine
the potential of fluorescent, pharmacological materials, while
representing perspective platforms for the creation of macro-
cyclic systems with the UV/Vis-NIR absorption.
erer Boekelheide as cycl[3.2.2]azines,[1] represent aromatic 5–5–
6 tricyclic compounds with an internal nitrogen atom and an
extended 10π electron conjugation system, which renders
them and their derivatives efficient stable n-type semiconduc-
tors,[2] UV/Vis absorbers,[3] blue and green-light emitting fluo-
rescent materials,[4–6] as well as promising candidates to be in-
volved in the π-expanded macrocycles. Such macrocyclic com-
pounds are extremely rare to the best of our knowledge being
presented by a few examples to date,[7,8] while they can exhibit
useful properties, primarily, absorption in the NIR range. The
substituted cycl[3.2.2]azine representatives have been shown to
possess pharmacological activity in binding to an estrogen re-
There are two general approaches to the synthesis of
cycl[3.2.2]azine core: cascade process involving the use of pre-
formed indolizines[15–20]and the process without the use of pre-
formed indolizines.[21,22] Since our main research interests lie in
the field of tetrapyrrolic macrocycles, in particular, phthalo-
cyanines,[23] which are assembled based on phthalic acid deriv-
atives, we focused our efforts on ortho-dicarboxylic acid deriva-
tives of cycl[3.2.2]azines. Recently, we reviewed this issue[24] and
showed that mainly diesters are reported to date with only few
publications describing the acids themselves, as well as their
anhydrides and hydrazides. As ortho-dinitriles are one of the
most suitable precursors of phthalocyanines and other anne-
lated porphyrazines, the present work is devoted to the prepa-
ration of the first cyclazine based dicarbonitriles with the use
of preformed indolizines, namely, 1,2-dicyano-3-arylcycl[3.2.2]-
azines (3-arylcycl[3.2.2]azine-1,2-dicarbonitriles), their unambig-
uous structural characterization and study of their photophysi-
cal properties.
[a] A. S. Starikov, Dr. V. V. Kalashnikov, Dr. P. A. Tarakanov, A. O. Simakov,
Dr. V. V. Tkachev, Dr. A. V. Yarkov, V. P. Kazachenko, Dr. Prof. L. G. Tomilova,
Dr. V. E. Pushkarev
Institute of Physiologically Active Compounds, Russian Academy of Sciences,
1 Severny proezd, Chernogolovka 142432, Moscow Region,
Russian Federation
E-mail: andreistarikov1994@mail.ru
pushkarev@ipac.ac.ru
[b] Dr. S. V. Simonov
Institute of Solid State Physics, Russian Academy of Sciences,
2 Academician Ossipyan street, Chernogolovka 142432, Moscow Region,
Russian Federation
[c] Dr. V. V. Tkachev, A. V. Chernyak
Institute of Problems of Chemical Physics, Russian Academy of Sciences,
1 Academician Semenov avenue, Chernogolovka 142432, Moscow Region,
Russian Federation
Scheme 1 shows the synthesis of title compounds starting
from commercially available acetophenone 1a and p-tert-
butylacetophenone 1b obtained according to the literature
method.[25]
[d] Dr. F. E. Zhurkin
Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques
UMR CNRS 8601, Université de Paris
45 rue des Saints-Pères 75006 Paris, France
Bromination of 1a,b by the modified procedure[26] gave
phenacyl bromides 2a,b, which then quaternized α-picoline
into corresponding water-soluble bromides 3a,b, followed by a
base-mediated Chichibabin conversion of the latter to 2-aryl-
[e] Dr. Prof. L. G. Tomilova, Dr. V. E. Pushkarev
Department of Chemistry, M.V. Lomonosov Moscow State University,
1 Leninskie Gory, Moscow 119991, Russian Federation
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under https://doi.org/10.1002/ejoc.202000958.
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Scheme 1. Synthesis of 3-arylcycl[3.2.2]azine-1,2-dicarbonitriles. Conditions: (a) (COCl)2, cat. DMF, DCE, 85 °C; (b) SOCl2, cat. DMF, 75 °C; (c) NH3, CHCl3, r.t.;
(d) POCl3, DMF, 0 °C to r.t.; (e) (CF3CO)2O, NEt3, THF, 0 °C to r.t. See the Supporting Information for details.
Scheme 2. Attempted synthesis of imide based on 8a.
indolizines 4a,b.[27] The [8 + 2] cycloaddition reaction involving chlorides and then amides (Scheme 1) by analogy with the
4a,b and dimethylacetylenedicarboxylate (DMAD) in the pres- method proposed by Linstead for the synthesis of 2,3-di-
ence of palladium on charcoal by the modified Boekelheide cyanothiophene[31] and improved by Stuzhin and co-authors
technique[16] afforded cycl[3.2.2]azine 1,2-diesters 5a,b.
to the one-pot procedure for the synthesis of a series of 2,3-
dicyanothianaphthenes.[32] In order to increase the yields of the
originally planned targets – nitriles 7a,b, we also chose the one-
pot option, and it turned out that the use of thionyl chloride in
the preparation of intermediate acid chlorides under the condi-
tions described in the literature sources[31,32] unexpectedly
leads (Scheme 1, condition sequence b,c,d) to 4-chlorosubsti-
tuted products 7c,d. The possibility of chlorination of the
cycl[3.2.2]azine core at the 4-position was additionally con-
firmed by the interaction of thionyl chloride with diester 5a
(Scheme 3) obtaining derivative 5a-Cl. Note that upon the
treatment of 5a with phosphoryl chloride under conditions (d)
of Scheme 1, the chlorinating effect was not detected.
Further conversion of 1,2-diesters to 1,2-dicarbonitriles im-
plies intermediate formation of 1,2-diamide derivatives. At-
tempts to conduct direct ammonolysis of the ester groups
based on known procedures,[28] as well as their modifications
at increased pressure, for example, the interaction of 5a with a
saturated solution of ammonia in methanol at 50 °C in a sealed
tube, led to the formation of only trace amounts of target 1,2-
diamides. For this reason, diesters 5a,b were quantitatively hy-
drolyzed[29] to diacids 6a,b, which were further used in the syn-
thesis of dinitriles 7a–d. An attempt to obtain 7a through the
intermediate formation of the corresponding anhydride 8a and
further imide (Scheme 2), by analogy with the synthesis of
phthalimide,[30] failed since heating of 8a with urea led to a
mixture of partially decarboxylated monoamide products 9a.
In order to avoid chlorination at the 4-position and obtain
dinitriles 7a,b, oxalyl chloride[33] was used in the synthesis of
The synthesis of nitriles 7 turned out to be possible by se- intermediate acid chlorides (Scheme 1, condition sequence
quential conversion of diacids 6a,b into the corresponding a,c,d). It was also shown that the replacement of phosphoryl
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Scheme 3. Chlorination of 5a with thionyl chloride.
chloride at the stage of diamide dehydration with trifluoro-
acetic anhydride (Scheme 1, condition sequence a,c,e) under
conditions previously developed for benzamide derivatives[34]
allows increasing the yield of 7a,b by 10–15 %.
The structure of target dinitriles 7a–d, as well as a number
of their previously undescribed precursors, was unambiguously
confirmed based on the data of IR spectroscopy, mass spec-
trometry, elemental analysis, as well as 1H and 13C NMR spectro-
scopy with the full signal assignment made utilizing two-
Figure 1. Overlay of 1H-13C HSQC and HMBC spectra of 7b in CDCl3. HMBC
signals are marked by bold dashes. Inset (pink line) shows the 1H spectrum
of 7d in CDCl3.
1
dimensional homonuclear H-1H (COSY, NOESY) and heteronu-
clear 1H-13C (HSQC, HMBC) correlation techniques (Figure 1 and
S1–S57, Supporting Information). All synthesized compounds,
except for indolizines 4, have excellent air stability. Their melt-
ing points are generally around 200 °C. Importantly, esters 5
and nitriles 7 melt without decomposition, which is a crucial
point in the light of further macrocyclization studies. The
molecular structures of indolizine 4b (Figure S58, Supporting
Information), diester 5a (Figures S59 and S60, Supporting Infor-
mation) and 4-position chlorinated dinitrile 7d (Figure 2, Table
S1, Supporting Information) were determined using the X-ray
diffraction analysis. The obtained X-ray data show planar geom-
etries of the cycl[3.2.2]azine cores in both diester 5a and di-
nitrile 7d molecules with the lowest bond length values charac-
teristic for the inner C-N1 bonds indicating moderate involve-
ment of central N1 atom into the peripheral π-conjugation cir-
cuit.
The phenomenon of chlorination of the cycl[3.2.2]azine core
at the 4-position, discovered using compounds 5 and 6 as an
example (Scheme 1, conditions b), requires additional consider-
ation. The literature describes some cases of chlorination of aro-
matic compounds in the SOCl2/DMF system,[35–37] however the
detail mechanism of this reaction is still unclear. It was as-
Figure 2. Crystal structure of 7d. Top: top view. Bottom: side view. Thermal
ellipsoids are set at the 50 % probability level.
sumed[36] that thionyl chloride plays the role of an electrophilic chloride of 6a and 7a models (Figure 3) reveals the relatively
agent and is capable of attacking electron-rich positions in aro- negative electrostatic potential values combined with the suffi-
matic cycles by analogy with the SEAr mechanism. Electrophilic ciently low average local ionization energy values in the C4
substitution reactions (nitration, halogenation, acylation) are atom area, which is consistent with the observed chlorination
also characteristic of cycl[3.2.2]azine heterocycle.[38,39] We per- regioselectivity of cyclazines 5 and 6 by thionyl chloride and
formed an analysis of the molecular and electronic structures confirms exactly electrophilic (SEAr) mechanism of this reaction.
using the examples of acid chloride of 6a and 7a,c models, Moreover, a comparative analysis of the data given in Figure 3
which were obtained on the basis of quantum-chemical calcula- for the 7a and 7c models shows that chlorination at the
tions at the BP86/def2-TZVP level of theory (Tables S2–S4, Sup- 4-position deactivates the cycl[3.2.2]azine core to subsequent
porting Information). The values of the main structural parame- electrophilic reactions, while the phenyl substituent retains its
ters for the 7c model show good convergence with the X-ray electrophilic activity, in fact, being almost excluded from the π-
diffraction analysis data for dinitrile 7d (Table S5, Supporting conjugation with the cycl[3.2.2]azine moiety due to a non-zero
Information; the maximum deviation of bond lengths is angle of their relative rotation. This suggests the possibility of
0.028 Å), which indicates the legitimacy of using this model to further electrophilic substitution at the phenyl group under
determine structure-property correlations. Thus, an analysis of more severe conditions. Such a high activity of the cycl[3.2.2]-
energy parameters on the molecular surfaces[40,41] in the acid azine core in relation to electrophilic agents despite the pres-
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ence of two electron-withdrawing carboxyl or nitrile groups in
the 1- and 2-positions can be explained by its electron-rich na-
ture. Thus, according to the natural atomic orbital analysis data
for the 7a model, the local population of the central nitrogen
atom pz-orbital is 1.49e, while the cumulative local population
of ten carbon pz-orbitals composing the cycl[3.2.2]azine core is
10.4e (Table S6, Supporting Information), which predicts the
electron-rich nature of cycl[3.2.2]azine heteroaromatic system.
These results efficiently supplement the X-ray data for com-
pounds 5a and 7d indicating that in spite of quite moderate
involvement of central N1 atom into the peripheral π-conjuga-
tion, it nevertheless plays a key role in the formation of an
electron-rich aromatic system of cycl[3.2.2]azines. Apparently,
the electron-rich nature of the cycl[3.2.2]azine heterocycle is
also the main reason for the inhibition of ammonolysis of esters
5a,b to the corresponding diamides.
Figure 4. UV/Vis absorption (dashed lines) and fluorescence (solid lines, λex
410 nm, ca. 3.0 × 10–6
) spectra of 7a,c in toluene. The insets show the
solutions under the given conditions.
=
M
For this purpose, we proposed a several stage route, which in-
volves a one-pot procedure at the final stage. Structures of the
target products were unambiguously characterized by a com-
plex of methods including 1H, 13C NMR and X-ray diffraction
analysis. Quite unexpectedly, chlorination of cycl[3.2.2]azine-
1,2-dicarboxylic acid derivatives with thionyl chloride at the
4-position has been found. According to the DFT calculations,
this phenomenon is provided by the electron-rich nature of
cycl[3.2.2]azine heterocycle and can apparently be realized by
the electrophilic (SEAr) mechanism. Unsubstituted at the 4-posi-
tion cycl[3.2.2]azine-1,2-dicarbonitriles show good photophysi-
cal characteristics, which makes them promising blue fluoro-
phores for OLED applications. In turn, the found dependence
of the fluorescent properties of cycl[3.2.2]azine based 1,2-di-
carbonitriles on the solvent polarity opens up the prospect of
their application as visualizing agents in biological systems.
Experimental Section
Figure 3. Electrostatic potentials (left) and average local ionization energies
(right) on the molecular surfaces of acid chloride of 6a and dinitriles 7a,c
calculated at the BP86/def2-TZVP level of theory.
Deposition Numbers 2003545, 2003546 and 2003779 contain the
supplementary crystallographic data for this paper. These data are
provided free of charge by the joint Cambridge Crystallographic
Data Centre and Fachinformationszentrum Karlsruhe Access Struc-
tures service www.ccdc.cam.ac.uk/structures.
Target dinitrile compounds 7a–d possess good extinction
coefficients (ε ≥ 104 L mol–1 cm–1) in the blue spectral region at
435–450 nm, as well as blue fluorescence at 450–480 nm
with a Stokes shift of about 1200 cm–1 (Table S7, Supporting
Information). Upon introduction of a chlorine atom into the
4-position, the fluorescence quantum yields (ΦF) decrease by
almost an order of magnitude from ΦF ≈ 0.3 0.03 to
ΦF ≈ 0.04 0.004 for 7a,b and 7c,d, respectively (Figure 4 and
S61, Supporting Information), which is most likely connected
with a decay of singlet excited state by the internal conversion.
In addition, a significant dependence of the fluorescence quan-
tum yield on the solvent polarity is observed in the case of
7a,b: upon transition from DMSO to toluene, the ΦF values
show an almost 1.5-fold increase. This renders cycl[3.2.2]azine
based dinitriles promising candidates for the visualization of
biological objects.
Supporting Information (see footnote on the first page of this
article): Please see the Supporting Information for more details.
Conflict of Interest
The authors declare no competing financial interest.
Acknowledgments
NMR experiments have been performed using the equipment
of the Multi-User Analytical Center of IPCP RAS and the facilities
provided by the Center of Collective Use of IPAC RAS. Synthetic,
spectral and theoretical studies performed in this work were
supported by the Russian Foundation for Basic Research (Grant
19-03-01038), Council under the President of the Russian Feder-
Thus, based on easily accessible precursors, we synthesized ation for State Support of Young Scientists and Leading Scien-
the first representatives of cycl[3.2.2]azine-1,2-dicarbonitriles. tific Schools (Grant MD-3847.2019.3) and performed within the
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[19]
[20]
P. Li, X. Zhang, X. Fan, J. Org. Chem. 2015, 80, 7508–7518.
H. Hu, G. Li, W. Hu, Y. Liu, X. Wang, Y. Kan, M. Ji, Org. Lett. 2015, 17, 1114–
1117.
Y. Yu, Y. Feng, R. Chauvin, S. Ma, L. Wang, X. Cui, Org. Lett. 2018, 20,
4209–4212.
C. C. Chintawar, M. V. Mane, A. G. Tathe, S. Biswas, N. T. Patil, Org. Lett.
2019, 21, 7109–7113.
V. E. Pushkarev, L. G. Tomilova, V. N. Nemykin, Coord. Chem. Rev. 2016,
319, 110–179.
F. E. Zhurkin, V. E. Pushkarev, L. G. Tomilova, Curr. Org. Synth. 2015, 12,
378–384.
J. C. Butler, L. L. Ferstandig, R. D. Clark, J. Am. Chem. Soc. 1954, 76, 1906–
1908.
E. W. Garbisch, J. Org. Chem. 1965, 30, 2109–2120.
G. S. Singh, E. E. Mmatli, Eur. J. Med. Chem. 2011, 46, 5237–5257.
J.-C. Harmange, M. M. Weiss, J. Germain, A. J. Polverino, G. Borg, J. Bready,
D. Chen, D. Choquette, A. Coxon, T. DeMelfi, L. DiPietro, N. Doerr, J. Es-
trada, J. Flynn, R. F. Graceffa, S. P. Harriman, S. Kaufman, D. S. La, A. Long,
M. W. Martin, S. Neervannan, V. F. Patel, M. Potashman, K. Regal, P. M.
Roveto, M. L. Schrag, C. Starnes, A. Tasker, Y. Teffera, L. Wang, R. D. White,
D. A. Whittington, R. Zanon, J. Med. Chem. 2008, 51, 1649–1667.
Y. Tominaga, Y. Shiroshita, T. Kurokawa, H. Gotou, Y. Matsuda, A. Hosomi,
J. Heterocycl. Chem. 1989, 26, 477–487.
framework of the State Assignment of 2020 (Theme 45.5 Crea-
tion of compounds with given physicochemical properties,
№ 0090-2019-0003). Single-crystal X-ray structural study of
compounds 4b and 5a was performed within the framework of
the State Assignment of 2020 (№ 0089-2019-0011).
[21]
[22]
[23]
[24]
[25]
Keywords: Cycl[3.2.2]azines · 1,2-Dicarbonitriles ·
Chlorination · Electrophilic substitution · UV–vis
fluorophores
[1] V. Boekelheide, R. J. Windgassen, J. Am. Chem. Soc. 1958, 80, 2020.
[2] A. Skabeev, U. Zschieschang, Y. Zagranyarski, H. Klauk, K. Müllen, C. Li,
Org. Lett. 2018, 20, 1409–1412.
[3] Y. Shigemitsu, M. Uejima, T. Sato, K. Tanaka, Y. Tominaga, J. Phys. Chem.
A 2012, 116, 9100–9109.
[4] T. Mitsumori, M. Bendikov, O. Dautel, F. Wudl, T. Shioya, H. Sato, Y. Sato,
J. Am. Chem. Soc. 2004, 126, 16793–16803.
[5] Y.-M. Shen, G. Grampp, N. Leesakul, H.-W. Hu, J.-H. Xu, Eur. J. Org. Chem.
2007, 3718–3726.
[6] É. Lévesque, W. S. Bechara, L. Constantineau-Forget, G. Pelletier, N. M.
Rachel, J. N. Pelletier, A. B. Charette, J. Org. Chem. 2017, 82, 5046–5067.
[7] M. Suzuki, T. Hoshino, S. Neya, Org. Lett. 2014, 16, 327–329.
[8] W. Zheng, Y. Zhao, W.-H. Zhuang, J.-J. Wu, F.-Z. Wang, C.-H. Li, J.-L. Zuo,
Angew. Chem. Int. Ed. 2018. 57, 15384–15389; Angew. Chem. 2018, 130,
15610.
[9] A. S. Jørgensen, P. Jacobsen, L. B. Christiansen, P. S. Bury, A. Kanstrup,
S. M. Thorpe, S. Bain, L. Narum, K. Wassermann, Bioorg. Med. Chem. Lett.
2000, 10, 399–402.
[10] A. S. Jørgensen, P. Jacobsen, L. B. Christiansen, P. S. Bury, A. Kanstrup,
S. M. Thorpe, L. Narum, K. Wassermann, Bioorg. Med. Chem. Lett. 2000,
10, 2383–2386.
[11] F. Schröder, S. Franke, W. Francke, H. Baumann, M. Kaib, J. M. Pasteels, D.
Daloze, Tetrahedron 1996, 52, 13539–13546.
[12] F. Shröder, V. Sinnwell, H. Baumann, M. Kaib, Chem. Commun. 1996, 18,
2139–2140.
[13] F. Schröder, V. Sinnwell, H. Baumann, M. Kaib, W. Francke, Angew. Chem.
Int. Ed. Engl. 1997, 36, 77–80; Angew. Chem. 1997, 109, 161.
[14] Z. Wu, Q. Wang, J. Wang, H. Dong, X. Xu, Y. Shen, H. Li, W. Zhang, Org.
Lett. 2018, 20, 7567–7570.
[15] S. K. Ghosh, D. Ghosh, R. Maitra, Y.-T. Kuoand, H. M. Lee, Eur. J. Org. Chem.
2016, 34, 5722–5731.
[16] A. Galbraith, T. Small, R. A. Barnes, V. Boekelheide, J. Am. Chem. Soc.
1961, 83, 453–458.
[26]
[27]
[28]
[29]
[30]
P. M. Lorz, F. K. Towae, W. Enke, R. Jäckh, N. Bhargava, W. Hillesheim,
Ullmann's Encycl. Ind. Chem. 2007, 131–180.
[31]
[32]
R. P. Linstead, E. G. Noble, J. M. Wright, J. Chem. Soc. 1937, 911–921.
E. S. Taraymovich, A. B. Korzhenevskii, Y. V. Mitasova, R. S. Kumeev, O. I.
Koifman, P. A. Stuzhin, J. Porphyrins Phthalocyanines 2011, 15, 54–65.
R. Salmon, Encycl. Reagents Org. Synth. 2001, DOI: https://doi.org/
10.1002/047084289X.ro017.
M. Rowley, J. J. Kulagowski, A. P. Watt, D. Rathbone, G. I. Stevenson, R. W.
Carling, R. Baker, G. R. Marshall, J. A. Kemp, A. C. Foster, S. Grimwood, R.
Hargreaves, C. Hurley, K. L. Saywell, M. D. Tricklebank, P. D. Leeson, J.
Med. Chem. 1997, 40, 4053–4068.
O. Lohse, Synth. Commun. 1996, 26, 2017–2025.
O. Soidinsalo, K. Wähälä, Phosphorus Sulfur Silicon Relat. Elem. 2007, 182,
2761–2767.
I. A. El-Sakka, N. A. Hassan, J. Sulfur Chem. 2005, 26, 33–97.
R. J. Windgassen, W. H. Saunders, V. Boekelheide, J. Am. Chem. Soc. 1959,
81, 1459–1465.
M. A. Jessep, D. Leaver, J. Chem. Soc., Perkin Trans. 1 1980, 1319–1323.
P. Sjoberg, J. S. Murray, T. Brinck, P. Politzer, Can. J. Chem. 1990, 68, 1440–
1443.
[33]
[34]
[35]
[36]
[37]
[38]
[39]
[40]
[41]
P. Politzer, J. S. Murray, M. C. Concha, Int. J. Quantum Chem. 2002, 88,
19–27.
[17] E. V. Babaev, V. V. Simonyan, K. Y. Pasichnichenko, V. M. Nosova, A. V.
Kisin, K. Jug, J. Org. Chem. 1999, 64, 9057–9062.
[18] M. Aginagalde, Y. Vara, A. Arrieta, R. Zangi, V. L. Cebolla, A. Delgado-
Camón, F. P. Cossío, J. Org. Chem. 2010, 75, 2776–2784.
Received: July 8, 2020
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