Electrochemical reactivity of S-phenacyl-O-ethyl-xanthates in hydroalcoholic (MeOH/H2O 4:1) and anhydrous acetonitrile media

Article abstract of DOI:10.1016/j.electacta.2021.138239

The electrochemical behavior of a series of S-phenacyl-O-ethyl-xanthates (O-ethyl-dithiocarbonate acetophenone derivatives) in hydroalcoholic (MeOH/H₂O 4:1) and anhydrous media (ACN/TBAPF₆) using carbon electrodes was studied. Cyclic voltammetry showed in hydroalcoholic media only two cathodic waves, whereas in ACN one anodic and two cathodic waves were present. The first cathodic wave corresponded to the reduction of the phenylketone group, whereas the first anodic was attributed to the xanthate unit. Macroelectrolysis on graphite and vitreous carbon at anodic and cathodic potentials, let us to explore the synthetic potential of this electrochemical reactions. With some compounds in hydroalcoholic media and using carbon electrodes, polymeric material was deposited on the electrode impeding the reaction; this deposit was characterized by AFM and SEM-EDS. The electroreduction on Ti electrode overcome this problem and gave the corresponding acetophenones (>95%). On the other hand, in ACN, small quantities of the dimeric 1,4-dicarbonyl compounds X-PhCOCH₂CH₂COPh-X (7–15%), as well as the corresponding acetophenones (ca. 50%) were isolated. Oxidation macroelectrolysis showed a very complicated transformation without synthetic value. The reaction mechanism for the reduction and the homolytic dissociation into the phenacyl radical was supported by DFT calculations.

Full text of DOI:10.1016/j.electacta.2021.138239

Electrochimica Acta 380 (2021) 138239
Contents lists available at ScienceDirect
Electrochimica Acta
journal homepage: www.elsevier.com/locate/electacta
Electrochemical reactivity of S-phenacyl-O-ethyl-xanthates in
hydroalcoholic (MeOH/H2O 4:1) and anhydrous acetonitrile media
Ernesto Emmanuel López-Lópeza,1, Sergio J. López-Jiméneza,1, Joaquín Barroso-Floresa,b
Esdrey Rodríguez-Cárdenasc, Melina Tapia-Tapia a,b, Gustavo López-Téllezb,
Luis D. Mirandab,∗, Bernardo A. Frontana-Uribea,b,∗
,
a Centro Conjunto de Investigación en Química Sustentable UAEM-UNAM, Carretera Toluca-Ixtlahuaca Km 14.5, Toluca, Estado de México 50200, México
b Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Coyoacán, CDMX 04510, México
c Universidad Politécnica de Otzolotepec, Barrio Dos Caminos, Villa Cuauhtémoc, Otzolotepec, Estado de México 52080, México
a r t i c l e i n f o
a b s t r a c t
Article history:
The electrochemical behavior of a series of S-phenacyl-O-ethyl-xanthates (O-ethyl-dithiocarbonate ace-
tophenone derivatives) in hydroalcoholic (MeOH/H2O 4:1) and anhydrous media (ACN/TBAPF6) using
carbon electrodes was studied. Cyclic voltammetry showed in hydroalcoholic media only two cathodic
waves, whereas in ACN one anodic and two cathodic waves were present. The first cathodic wave cor-
responded to the reduction of the phenylketone group, whereas the first anodic was attributed to the
xanthate unit. Macroelectrolysis on graphite and vitreous carbon at anodic and cathodic potentials, let us
to explore the synthetic potential of this electrochemical reactions. With some compounds in hydroalco-
holic media and using carbon electrodes, polymeric material was deposited on the electrode impeding
the reaction; this deposit was characterized by AFM and SEM-EDS. The electroreduction on Ti electrode
overcome this problem and gave the corresponding acetophenones (>95%). On the other hand, in ACN,
small quantities of the dimeric 1,4-dicarbonyl compounds X-PhCOCH2CH2COPh-X (7–15%), as well as the
corresponding acetophenones (ca. 50%) were isolated. Oxidation macroelectrolysis showed a very com-
plicated transformation without synthetic value. The reaction mechanism for the reduction and the ho-
molytic dissociation into the phenacyl radical was supported by DFT calculations.
Received 30 December 2020
Revised 8 March 2021
Accepted 20 March 2021
Available online 26 March 2021
© 2021 Elsevier Ltd. All rights reserved.
1. Introduction
reagents incompatible with an industrial scale-up. Recently it has
been reported the use of visible light to activate xanthate deriva-
Radical species are useful intermediaries to carry out the syn-
thesis of complex molecules and are complementary to the routes
that involve ionic species [1]. The classical methodologies for ac-
cessing these reactive intermediates require the use of initiators
typically diazocompounds, and peroxides or boron species in the
presence of oxygen [2]. After an activation (Thermal or photo-
chemical Fig. 1A) these compounds suffer an homolytic reaction
that produces radical species, which react with precursors contain-
ing bonds with suitable bond dissociation energies (For example
dithiocarbonates known as xanthates, N-hydroxypyridine-2-thione
ester ‘‘Barton-ester’’ Fig. 1A or halogen-C bond, Fig. 1B) [3]. Even if
these techniques are effective, the experimental protocols require
high temperatures, strong UV-light irradiation, the use of explosive
tives, which contain a specially designed xanthogenate and let the
radical addition to unsaturated systems in good yields [4]. Free
radicals production via photoredox catalysis (Fig. 1C) is a promis-
ing approach for making the reaction in milder conditions, nev-
ertheless requires the use of specialized catalyst, most of them Ir
or Ru derivatives, difficulting large scale production [5,6]. Single
Electron Transfer (SET) mechanism operates to produce the tar-
get radical, but some photoredox catalysts can also adopt a hydro-
gen abstraction reactivity. Electron transfer strategy (Fig. 1D) us-
ing reductants/oxidants in stoichiometric amount, has as a major
inconvenience the chemical waste of the exhausted redox specie
and the poor selectivity of the redox potential of the compounds
used to promote SET [7]. Particularly interesting to carry out elec-
tron transfer reactions in organic chemistry is the electrochemi-
cal method, due to the possibility of using the electron as reagent,
without use of chemicals, which generate chemical waste or have
high toxicity [8–10].
∗
Corresponding authors.
E-mail addresses: lmiranda@unam.mx (L.D. Miranda), bafrontu@unam.mx (B.A.
Frontana-Uribe).
1
These authors contributed equally to this investigation.
https://doi.org/10.1016/j.electacta.2021.138239
0013-4686/© 2021 Elsevier Ltd. All rights reserved.

E.E. López-López, S.J. López-Jiménez, J. Barroso-Flores et al.
Electrochimica Acta 380 (2021) 138239
Fig. 1. Strategies for generating radicals. (A) and (B): Traditional methods which generally rely on a initiation step with high-energy compounds, and require precursors with
adequate bond dissociation energy. (C) Photoredox catalysts approach. (D) Reductive and oxidative Single Electron Transfer strategies.
Scheme 1. Workflow, electrochemical reduction and oxidation of phenacyl-xanthate derivatives and study of the reactivity in hydroalcoholic and ACNahn media.
Among the most useful free radicals precursors, xanthates
has been widely explored starting from the pioneering studies
of Barton [11] and followed by Zard investigations [12,13,–14]
who demonstrated the possibility of forming C-C bonds through
the free radical species obtained from these precursors. Particu-
larly about dithiocarbonate acetophenone derivatives (S-phenacyl-
xanthate derivatives) studied in this work, it has been reported its
direct photochemical reaction, which breaks the labile C-S bond to
obtain 1,4-dicarbonyl compounds [15]. This reactivity was used re-
cently to propose a hydroxyl protection group [16] but the SET re-
action of the S-phenacyl-xanthates using redox reagents has not
been explored yet. Therefore, their electrochemical transformation
through SET from an electrode (reduction pathway, Scheme 1) or
towards the electrode (oxidation pathway, Scheme 1) using an
electrochemical cell, is a promising alternative to generate radi-
cal species useful in organic synthesis, as shows the diverse re-
views published [17,18]. In the case of the of xanthate derivatives,
exists very few reports of the electrochemistry and electrochem-
ical application in synthesis of these compounds. Thus, the elec-
trochemical oxidation of series of S-phenacyl xanthates were re-
ported by Barba et al. [19] using CH3CN-H2O (1%)/LiClO4 (0.1 M)
on Pt anode, the resulting product was the corresponding thiocar-
bonate isolated in good yields. In this transformation water was
required in the electrolyte solution to obtain the final product.
On the other hand, there are only two reports where the reduc-
tive behavior of the S-phenacyl xanthate was studied, the first in
DMFanh/LiClO4 at Hg cathode [20]; these electrochemical condi-
tions are incompatible with the modern trends of synthetic or-
ganic electrochemistry [8] where Hg electrodes and the use of
LiClO4 are being limited due to toxicity and safeness respectively.
2

E.E. López-López, S.J. López-Jiménez, J. Barroso-Flores et al.
Electrochimica Acta 380 (2021) 138239
Besides, the transformation gave a mixture of compounds where
the interesting 1,4-dicarbonylic compound was obtained in low
yield. The second report is an electrochemical-type Barton des-
oxygenation reaction [21] also using a Hg and Pb cathode, show-
ing moderate yields. The bibliographic research done indicates the
scarce studies about the synthetic potential of the electrochemi-
cal transformation of these compounds. Therefore, in this contribu-
tion it is reported the anodic and cathodic behavior of S-phenacyl-
xanthates in hydroalcoholic (MeOH/H2O 4:1) and non-aqueous me-
dia (ACNanh/TBAPF6) (Scheme 1) using cyclic voltammetry and vit-
reous carbon and graphite electrodes. Macroelectrolysis let us to
explore the electrochemical transformation of these compounds in
both media.
NH4Cl saturated (50 mL) were added and the product was ex-
tracted (3 × 20 mL CH2Cl2). The organic layer was dried over an-
hydrous Na2SO4 and the solvent was removed under reduced pres-
sure giving the corresponding crude S-phenacyl-xanthate (88–95%
yield); recrystallization gave analytical samples.
2.1.4. Electroanalytical experiments
Cyclic voltammetry was performed, with a potentiostat Auto-
lab PGSTAT30 using a vitreous carbon electrode 3 mm diame-
ter (BASi) as working electrode (WE) and as counter electrode
(CE) a platinum wire. As reference electrode (RE) were used the
Ag/AgCl/KClsat for hydroalcoholic media (0.197 V vs SHE) or the
Ag/Ag+10 mM, TBAP 0.1 M in ACN for acetonitrile media (0.591 V
vs SHE) [22]. The experiments were carried out using sodium ac-
etate/acetic acid buffer 0.5 M pH=4.75 in a mixture of MeOH/water
4:1 or anhydrous acetonitrile (Aldrich, water content <0.001% wa-
ter) with TBAPF6 (overnight dried) 0.1 M as electrolyte. The scan
rate potential sweep was 0.1 Vs-1 in all the cases.
2. Experimental
2.1. Starting materials synthesis
2.1.1. Materials and purity
The following materials were used in this study: sodium
ethyl xanthogenate, (Aldrich, >95%), ACN (50 mL Aldrich, 99.5%),
phenacyl bromides, (Aldrich, 96–98% without other purification),
NaI (Aldrich, 99.5%), glacial AcOH (Aldrich, 99.7%), sodium acetate
2.1.5. Macroelectrolysis in hydroalcoholic media
25 mL of electrolytic solution (MeOH/water 4:1 sodium ac-
etate/acetic acid buffer 0.5 M pH=4.75) were added to each of the
two H-cell compartments (fritted glass #4, Fig. S1). The cell was
fitted with a 3 electrodes system where WE: vitreous carbon retic-
ulated (60 cm2), graphite (15 cm2) or titanium (5.3 cm2), CE: plat-
inum mesh (15 cm2) and RE: Ag/AgCl electrode. The electrolysis
were conducted bubbling N2 (5 min) before adding the phenacyl
xanthate derivative (0.035 mmol) into the cathodic compartment
and the N2 stream was maintained over the solution during the
electrolysis. The cell was magnetically stirred until total dissolu-
tion of the compound, the potential is set at −1.45 V vs Ag/AgCl
(Table 1) and the reaction was followed by TLC (toluene/ethyl ac-
etate 9:1) sampling with a long capillary. After the charge required
passed or total consumption of the starting material (ca. 4 h of
electrolysis), reaction was stopped, and the methanol was evapo-
rated in the rotary evaporator and the organic compounds were
extracted (3 × 25 mL AcOEt) and the organic extracts were brine
washed. The organic layer was dried over anhydrous Na2SO4 and
the solvent was removed under reduced pressure giving the cor-
responding crude of reaction. The products were separated by col-
umn chromatography (SiO2) using mixtures of Hexane-AcOEt.
ꢀR
(Aldrich, 99%), Celite (Aldrich). Solvents methanol, hexane, EtOAc,
CH2Cl2 as well as Na2SO4, NH4Cl were Tecsiquim 98% min. CDCl3
(Cambridge isotope Labs, D% 99.8 with 0.05% V/V TMS), Acetone
-D6 (Cambridge isotope Labs, D% 99.9), Thin layer chromatogra-
phy (TLC, aluminum sheets precoated with silica gel Merck Silica
gel 60 F254). Column chromatography: silica gel (Macherey-Nagel
230–400 mesh).
2.1.2. General method for the synthesis of S-phenacyl-xanthates
(1a-1f)
To a solution of 5.2 mmol of sodium O-ethyl dithiocarbonate
(sodium ethyl xanthogenate) in 50 mL ACN, were added 4.5 mmol
phenacyl bromide, and the mixture was stirred for 3.5 h in the
darkness (Aluminum foil); the reaction was followed by thin layer
chromatography. After total consumption of the halogenated com-
pound, the solvent was removed under rotary evaporation. The
crude was supported on celite to perform a percolation over silica
gel with hexane, and the product was recovered with the organic
solvent. Removal of solvent under reduced pressure gave the cor-
responding pure (NMR purity >95%) S-phenacyl xanthate in high
yields.
2.1.6. Macroelectrolysis in anhydrous ACN
In a 50 mL per compartment cell type H (fritted glass #4,
Fig. S1), 25 mL of anhydrous acetonitrile (Aldrich, water content
<0.001% water) with TBAPF6 (overnight dried) 0.1 M were added
per compartment. The cell was fitted with a 3 electrodes sys-
tem where WE: vitreous carbon reticulated (60 cm2), CE: plat-
inum mesh (15 cm2) and RE: Ag/Ag+/10 mM Ag+ TBAP 0.1 M.
The electrolysis was conducted bubbling N2 (5 min) before adding
the phenacyl xanthate derivative (0.035 mmol) into the cathodic
compartment and the N2 stream was maintained over the solution
during the electrolysis. The compound added into the WE com-
partment and the cell was magnetically stirred until total disso-
lution of the compound. The potential is set at the required poten-
tial (Table 3) and the reaction was followed by TLC (toluene/ethyl
acetate 9:1) sampling with a long capillary. After the charge re-
quired passed or total consumption of the starting material (ca.
4 h of electrolysis), reaction was stopped, and the ACN was evap-
orated in the rotary evaporator and the organic compounds were
extracted (3 × 25 mL AcOEt) and the organic extracts were brine
washed. The organic layer was dried over anhydrous Na2SO4 and
the solvent was removed under reduced pressure giving the cor-
responding crude of reaction. The products were separated by col-
umn chromatography (SiO2) using mixtures of Hexane-AcOEt.
2.1.3. General procedure for the synthesis of S-phenacyl xanthates
(compounds 1a-1f) using filkenstain reaction
To a solution of 2 mmol phenacyl bromide in 10 mL dry ke-
tone was added NaI (10% mol). The solution was stirred for 1 h
in the darkness (Aluminum foil). After this time, 2.2 mmol of
sodium ethyl xanthogenate were added slowly and stirred for 2 h;
the reaction was followed by thin layer chromatography. The mix-
ture is filtered on celite washing with hexane and then the sol-
vent is removed under rotary evaporation. CH2Cl2 (20 mL) and
3

E.E. López-López, S.J. López-Jiménez, J. Barroso-Flores et al.
Electrochimica Acta 380 (2021) 138239
Table 1
Electrochemical data of S-phenacyl-xanthate derivatives (1a-1f) in hydroalcoholic media MeOH/H2O 4:1 pH=4.75 (Acetates
buffer 0.5 M) on vitreous carbon electrode and products obtained after the electroreduction reaction on diverse electrodes.
2.1.7. AFM and SEM-EDS experiments
O-Ethyl S-[2-(4-fluorophenyl)-2-oxoethyl] dithiocarbonate
(1d): white solid, m.p. 61–62 °C (lit [24]. 60–62 °C) 1H NMR
AFM equipment (ASYLUM RESEARCH MFP-3D Origin) working
in tapping mode with a scan area of 15 × 15 or 40 × 40 μm
was used to measure the film thickness and roughness with a tip
TESPA (BrukerꢀR ) scan rate 0.18 - 0.2 Hz. SEM equipment (JEOL
JSM-6510LV) furnished with an EDS OXFORD working at 10 kV in
a tungsten filament was used for the micrographies obtention.
(300 MHz, CDCl3) δ ppm, J Hz: 8.08–8.02 (dd, 2H, (3
J
1H–1H=8.3,
4
3
3
J
19 F-1H =4.5 Hz), 7.20–7.13 (dd, 2H
J
1H–1H=8.3,
J
19 F-1H
=8.5 Hz), 4.66–4.59 (m. 4H), 1.39, (t, 6.1, 3H). 13C NMR (75 MHz,
1
CDCl3) δ ppm: 213.30, 190.96, 167.88 (d,
131.35, 116.24, 115.95, 70.92, 43.50, 13.83.
J
19 F-13C =245 Hz),
O-Ethyl S-[2-(4-chlorophenyl)-2-oxoethyl] dithiocarbonate
(1e): cream solid, m. p. 65–67 °C (lit [17]. 63–65 °C) 1H NMR
(300 MHz, CDCl3) δ ppm, J Hz: 7.95 (d, 8.3, 2H), 7.46 (d, 8.3, 2H)
4.66–4.59 (m, 4H), 1.39 (t, 6.1, 3H). 13C NMR (75 MHz, CDCl3) δ
ppm: 213.22, 191.37, 140.36, 134.26, 129.96, 129.25, 70.96, 43.47,
13.83.
2.1.8. Spectroscopy and characterization of the compounds
O-Ethyl S-[2-(4-methoxyphenyl)-2-oxoethyl] dithiocarbonate
(1a): white solid, m.p. 69–70 °C (lit [17]. 68–69 °C) 1H NMR
(300 MHz, CDCl3) δ ppm, J Hz: 8.01 (d, 8.3, 2H), 6.97 (d, 8.3, 2H),
4.61 (m, 4H), 3.87 (s, 3H), 1.38 (t, 6.3, 3H). 13C NMR (75 MHz,
CDCl3) δ ppm: 213.56, 190.87, 164.12, 130.92, 128.88, 114.07, 70.71,
55.65, 43.44, 13.84.
O-Ethyl S-[2-(4-nitrophenyl)-2-oxoethyl] dithiocarbonate (1f):
white powder, m.p. 85–87 °C (lit [25]. 87–89 °C), 1H NMR
(300 MHz, CDCl3) δ ppm, J Hz: 8.37–8.33 (d, 7.9, 2H), 8.21–8.16
(d, 7.9, 2H), 4.68–4.60 (m, 4H), 1.41 (t, 6.1, 3H). 13C NMR (75 MHz,
CDCl3) δ ppm: 213.00, 191.45, 150.75, 140.56, 129.64, 124.16, 71.33,
43.66, 13.88.
O-Ethyl S-[2-(3,4-dihydroxyphenyl)-2-oxoethyl] dithiocarbon-
ate (1b): white solid, m.p. 119–120 °C (lit [23]. 118–120 °C) 1H
NMR (300 MHz, Acetone-D6) δ ppm, J Hz: 7.54–7.50 (m, 2H), 6.92-
6.89 (d, 8.2, 1H), 4.71- 4.67 (m, 1H), 4.61(q, 6.1, 2H) 1.34,(t, 6.1,
3H). 13C NMR (75 MHz, Acetone-D6) δ ppm: 214.71, 214.67, 190.82,
190.78, 153.16, 146.60, 128.63, 123.03, 115.89, 115.57, 71.11, 43.49,
43.21, 42.93, 13.86.
1-(4-methoxyphenyl)ethan-1-one (2a): white solid, m.p. 36–
38 °C (lit [26]. 37.4–38.8 °C), 1H NMR (300 MHz, CDCl3) δ ppm,
J Hz: 7.93(d, 7.9, 2H), 6.93(d, 7.9, 2H), 3.87 (s, 3H), 2.55 (s, 3H).
13C NMR (75 MHz, CDCl3) δ ppm: 196.92, 163.57, 130.69, 130.41,
113.77, 55.57, 26.46.
O-Ethyl S-[2-(phenyl)-2-oxoethyl] dithiocarbonate (1c): cream
solid, m. p. 31–33 °C (lit [17]. 31–32 °C 1H NMR (300 MHz, CDCl3)
δ ppm, J Hz: 8.01 (t, 8.2, 2H), 7.60–7.58 (m, 1H), 7.51–7.46 (m, 2H),
4.65–4.58 (m, 4H), 1.37 (t, 6.1, 3H). 13C NMR (75 MHz, CDCl3) δ
ppm: 213.24, 192.33, 135.84, 133.78, 128.84, 128.47, 70.73, 43.57,
13.76.
1-(3,4-dihydroxyphenyl)ethan-1-one (2b): cream solid; mp
114–115 °C (Lit [27]. mp 113 °C), 1H NMR (300 MHz, CDCl3) δ ppm,
J Hz: 7.49 (m, 1H), 7.39 (m, 1H), 6.88 (m, 1H), 3.74 (broad s, 2H,
2OH), 2.49 (s, 3H). 13C NMR (75 MHz, CDCl3) δ ppm: 198.8, 150.6,
144.5, 129.4, 122.9, 114.9, 114.5, 17.9.
4

E.E. López-López, S.J. López-Jiménez, J. Barroso-Flores et al.
Electrochimica Acta 380 (2021) 138239
Acetophenone (2c): yellow oil, 1H NMR (300 MHz, CDCl3) δ
ppm, J Hz: 7.93–7.90 (m, 2H), 7.58–7.54 (m, 1H), 7.48–7.43 (m, 2H),
2.53 (s, 3H). 13C NMR (75 MHz, CDCl3) δ ppm: 198.1, 137.1, 133.0,
128.4, 128.2, 26.9.
through a Filkenstein reaction. The yields were in accordance with
the reported literature obtaining 88–95% of the target compounds.
3.1. Electrochemical behavior of S-phenacyl-xanthate derivatives in
hydroalcoholic media
1-(4-fluorophenyl)ethan-1-ona (2d): colorless oil (lit [28]. col-
orless oil)1H NMR (300 MHz, CDCl3) δ ppm, J Hz: 7.99 (dd, 2H, (3
J
4
3
3
1H–1H=7.9,
J
19 F-1H =4.7 Hz), 7.12 (dd, 2H
J
1H–1H=7.9,
J
19 F-
The cyclic voltammetry of derivatives 1a-1f in MeOH/H2O 4:1
pH=4.75 (Acetates buffer 0.5 M) showed that these compounds are
reduced in two very close steps, the first around −1.32 to −1.42 V,
and the second between −1.55 and −1.82 V vs Ag/AgCl (Fig. 2).
Theoretical calculations (vide infra Theoretical calculations section)
showed that LUMO of the S-phenacyl-xanthate derivatives is delo-
calized over the aromatic carbonyl section of the molecules. Thus,
the first peak was assigned to the aromatic carbonyl and the sec-
ond to the product of this electron transfer [34] (see below). The
functional groups reduction potential is dependent of the chemi-
cal environment, as showed the case of thiocarbonate reduction of
6-pentyl-2H-pyran-2-ones derivatives [35], where in this case, the
reduction of the sulfur functional group occurs first than the conju-
gated ketone ester. In the other hand, the HOMO of the molecules
is localized at the dithiocarbonate unit, but its oxidation is not ob-
served, pointing that in this media on vitreous carbon electrode
water is oxidized first. Additional signals are attributed to the elec-
trochemical reactivity of other functional groups of compounds 1,
for example the reduction of the nitro group of the 4-nitro deriva-
tive 1f (at −0.75 V) and the oxidation (at 0.17 V) of the PhNHOH
[36] produced or the oxidation of the 3,4-dihidroxy-phenyl group
of compound 1b which occurs at 0.59 V (Table 1).
1H =8.3 Hz), 2.59 (s, 3H). 13C NMR (75 MHz, CDCl3) δ ppm: 196.3,
1
166.0 (d,
J
19F-13C =244 Hz), 133.41, 130.89, 115.6, 26.3.
1-(4-chlorophenyl)etan-1-one (2e): yellow oil (lit [24]. yellow
oil), 1H NMR (300 MHz, CDCl3) δ ppm, J Hz: 7.87 (d, 7.4, 2H), 7.41
(d, 7.4, 2H), 2.57 (s, 3H). 13C NMR (75 MHz, CDCl3) δ ppm: 194.8,
137.5, 133.4, 127.7, 126.9, 24.6.
1-(4-aminophenyl)etan-1-one (2f): white solid, mp 101–102 °C
(lit [29]. mp 95–103 °C), 1H NMR (300 MHz, CDCl3) δ ppm, J Hz:
7.80–7.75 (d, 8.0, 2H), 6.64–6.60 (d, 8.0, 2H), 4.20 (broad s, 2H),
2.48 (s, 3H). 13C NMR (75 MHz, CDCl3) δ ppm: 196.80, 151.69,
130.84, 127.33, 113.65, 26.11.
1,4-Bis(4ꢀ-methoxyphenyl)butane-1,4–dione (3a): white solid
mp. 100–102 °C, (lit [30]. 102–104 °C). 1H NMR (300 MHz, CDCl3)
δ ppm, J Hz: 7.99 (d, 8.1, 4H), 6.95 (d, 8.1, 4H), 3.89 (s, 4H, CH2),
3.79 (s, 6 H, OCH3). 13C NMR (75 MHz, CDCl3) δ ppm: 198.8, 160.5,
135.5, 132.3, 123.3, 122.4, 113.7, 57.6, 34.0.
1,4-diphenylbutane-1,4–dione (3c): white solid mp. 142–
144 °C, (lit [31]. 143–144 °C). 1H NMR (300 MHz, CDCl3) δ ppm,
J Hz: 8.10 – 7.99 (m, 4H), 7.63 – 7.54 (m, 2H), 7.54 – 7.43 (m,
4H), 3.47 (s, 4H). 13C NMR (75 MHz, CDCl3) δ ppm: 198.70, 136.82,
133.11, 128.59, 128.0, 32.67.
Macroelectrolysis (H-Type electrochemical cell divided by sin-
tered glass, Fig. S1) of the xanthate compounds 1a-1f was car-
ried out using at the beginning carbon-based electrodes (Reticu-
lated Vitreous Carbon = RVC and graphite) in the hydroalcoholic
media. The electrolysis potential was in all cases selected after
the first reduction peak of each starting compound (Table 1) ob-
tained on vitreous carbon. The electrolysis were TLC monitored,
and it was confirmed that the reactions with compounds 1a-1c
consumed 2.2–2.3 F/mol. This charge consumption is in accordance
with the isolated compounds, the corresponding acetophenone in
high yield (Table 1). Nitro-phenyl derivative 1f consumed more
8.7 F/mol which explains why the final product is the 4-amino-
acetophenone (2e reduction of xanthate and 6e reduction for the
nitro group). The plausible mechanism of this reduction in hydroal-
coholic medium is depicted in Scheme 2, where it is proposed
that the SET occurs from the electrode to the phenyl-carbonyl
group producing the radical anion specie, this eliminates the xan-
thogenate anion and give rise to the corresponding phenacyl radi-
cal. Nevertheless, the experiments showed that this radical species
is rapidly reduced again to the α carbonyl anion, which proto-
nates producing the observed products. This is proposed because
the 1,4-dicarbonyl compound, which would be obtained through
radical dimerization, was not detected in all the attempted condi-
tions and the major compound was the acetophenone derivative,
which is detected in the second peak of the cyclic voltammetry.
Ethyl xantogenate salt was recovered at the end of the electrolysis
supporting this mechanism, which is in accordance with the com-
putational calculus carried out (vide supra). This 2e mechanism re-
sembles the observed during photolysis of S-phenacyl xanthates 1,
where the radical intermediate, obtained by homolytic photocleav-
age, takes hydrogen atom from the protic solvent (iPr-OH) to yield
the acetophenone derivative in high yield [37].
1,4-Bis(4-fluorophenyl)butane-1,4–dione (3d): white solid mp.
139–140 °C, (lit [32]. 141–143 °C). 1H NMR (300 MHz, CDCl3)
4
δ ppm, J Hz: d = 8.1–8.07 (dd, 2H, (3
J
1H–1H=7.8,
J
19 F-1H
3
3
=4.6 Hz), 7.15–7.10 (dd, 2H
J
1H–1H=7.8,
J
19 F-1H =8.5 Hz),
3.40 (s, 4 H). 13C NMR (75 MHz, CDCl3) δ ppm: 197.0, 165.9 (d,
J
1
19 F-13C =244 Hz), 131.1, 130.7, 115.8, 32.3.
6-phenyl-1,2,4-oxadithiin-3-one (4c): cream solid mp. 82–
84 °C, 1H NMR (300 MHz, CDCl3) δ ppm, J Hz: 7–36 – 7.30 (m,
5H), 6.77 (s, 1H). 13C NMR (75 MHz, CDCl3) δ ppm: 190.0, 132.6,
130.2, 126.7, 126.35, 126.7, 109.2 MS: (EI; 70 eV) m/z (%) = 210
(M+). EA Anal. calcd. for C9H6O2S2: C, 51.41; H, 2.88.; found: C,
51.39; H, 2.85.
S-ethyl-S-(2-oxo-2-phenylethyl) carbonodithioate (5c): amber
liquid, 1H NMR (300 MHz, CDCl3) δ ppm, J Hz: 8.01–7.98 (m, 2H),
7.63 – 7.58 (m, 1H), 7.51 – 7.46 (m, 2H), 4.39 (s, 2H), 4.29 (q,
7.2, 2H), 1.3 (t, 7.2, 3H). 13C NMR (75 MHz, CDCl3) δ ppm: 192.2,
169.1, 134.7, 132.9, 127.9, 127.6, 63.3, 37.7, 13.4. MS: (EI; 70 eV) m/z
(%) = 240 (M+). EA. Anal. calcd. for C11 H12O2S2: C, 54.97; H, 5.03;
found: C, 54.95; H, 5.02.
2.1.9. Computational details
All calculations were performed with the Gaussian 09 rev D.01
suite of programs [33] at the B3LYP/6–31G(d,p) level of theory. All
molecules were optimized and the presence of a minimum on the
potential energy surface was ascertained by vibrational frequency
analysis from which the reported thermochemical parameters were
derived. To assess the main distribution of the unpaired electron in
the radical anions the spin density maps were plotted for the com-
puted compounds. Proposed reaction mechanisms were assessed at
the same level of theory.
3. Results and discussion
The starting compounds without substituent in the phenyl ring
(1c) or bearing halogen groups in 4-position (1d and 1e), gen-
erated a passive layer on the carbon electrode surface. This pas-
sive layer impedes the reaction to finish and current flow stop;
the electrodes are not easily reactivated. Reticulated vitreous car-
bon is useless after the electrolysis due to its porosity, fragility and
The studied S-phenacyl-xanthates (compounds 1a-1f, table 1)
were synthetized by a bimolecular nucleophilic substitution SN2
from the corresponding commercial α–bromo acetophenone and
sodium ethyl xantogenate or using the iodinated derivative
5

E.E. López-López, S.J. López-Jiménez, J. Barroso-Flores et al.
Electrochimica Acta 380 (2021) 138239
Fig. 2. Typical CV of A) Electrolytic media MeOH/H2O 4:1 acetate buffer, B) phenacyl-xanthate (1c), C) 4-Cl-phenacyl-xanthate (1e) and D) 4-MeO-phenacyl-xanthate (1a).
WE: VC, CE: Pt, RE: Ag/AgCl, v = 0.1 Vs−1
.
Scheme 2. Proposed mechanism for electroreduction of phenacyl-xanthate derivatives 1 in the hydroalcoholic media and in anhydrous acetonitrile.
6

E.E. López-López, S.J. López-Jiménez, J. Barroso-Flores et al.
Electrochimica Acta 380 (2021) 138239
Fig. 3. AFM micrographs of the (A) new reticulated vitreous carbon, (B) After 5 min electrolysis (−1.45 V) of compound 1d in hydroalcoholic media, (C) after total passivation
of the electrode (15 min).
Fig. 4. SEM micrograph of (A) graphite plate electrode, (B) after 10 min electrolysis (−1.45 V) of compound 1d in hydroalcoholic medium.
cleaning difficulty, graphite electrodes can be reused after a me-
chanical cleaning with a smooth sandpaper and towel paper. It is
well known that carbon electrodes can have strong adsorption of
organic molecules during its transformation [38,39] and metallic
electrodes can be an interesting alternative for the cathodic reac-
tions. In order to overcome this difficulty observed with 1c, 1d
and 1e, the reaction was carried out on titanium cathode using
the same conditions. This electrode with all the compounds stud-
ied did not passivate and let the reduction reaction to the cor-
responding acetophenone compounds in high yield (Table 1). De-
pending on the studied reaction, the potential determined at a
material electrode could be use in other material. Here consid-
ering the compounds and yields obtained with the charge pro-
vided are the same, it is possible to conclude that the potential
for the studied compounds using different electrode materials in
this electrolyte does not change considerably. This insensibility of
the reaction with the electrode material is observed in organic
electrochemistry in reactions which follow an outer-spere electron-
transfer mechanism [40,41]. Future electroanalytical studies will be
carried out specially to clarify this point.
In order to get insight about the nature of the deposits ob-
tained on the reticulated carbon vitreous (RVC), the electrodes
were studied by atomic force microscopy (AFM, Fig. 3) and scan-
ning electron microscopy coupled with energy dispersive X-ray
spectroscopy (SEM-EDS, Fig. 4). AFM images show the 3D repre-
sentation of the electrode morphology of the new RVC, the one
after 5 min of electrolysis (at −1.45 V) of compound 1d in hy-
droalcoholic media and the totally passivated with the deposit af-
ter 15 min of electrolysis (Figs. 3a and S6, 3b and 3c respec-
tively). As expected, the deposit accumulates as the electrolysis
progress and the surface changes drastically. The new RVC has
surface roughness of RMS=306 nm with and a value of Z min-
imum equal to 73 nm, after 5 min electrolysis it shows an in-
crease 52.18% (RMS=465.7 nm) as a result of material deposition.
The deposits are in the form of globular agglomerates with a ran-
dom non-homogeneous distribution on the electrode surface, re-
7

E.E. López-López, S.J. López-Jiménez, J. Barroso-Flores et al.
Electrochimica Acta 380 (2021) 138239
Fig. 5. Typical CV of (A) Electrolytic media ACN TBAPF6 0.1 M, (B) 4-MeO-phenacyl-xanthate (1a), (C) phenacyl-xanthate (1c) and (D) 4-F-phenacyl-xanthate (1d). Fc= Fc/Fc+
reversible system at 0.0 V as internal reference system. WE: VC, CE: Pt, RE: Ag/Ag+, v = 0.1 Vs−1
.
Table 2
Elemental analysis obtained by SEM-EDS of the passivated electrodes surface after −1.45 V reduction of compound 1d and 1e
in hydroalcoholic media on graphite electrode and its comparison with the clean graphite electrode. The result showed is the
range observed in 3 independent regions.
Electrode
C%
O%
F%
Cl%
S%
New
85.27 – 88.43
35.21 – 60.75
45.91 – 67.22
10.23 – 13.87
29.81 – 34.02
22.01 – 53.48
0
0
0.21 – 2.07
1.21 – 4.79
1.36 – 5.16
After electrolysis with compound 1d
After electrolysis with compound 1e
3.38 – 19.25
0
0.26 – 0.49a
5.92 – 21.45
a
This slight increment is explained by the presence of chloride ions adsorbed on the electrodes surface after recovering
the passivated electrode (See experimental section for details). The recovering graphite electrodes involved (a) Gentle abrasion
with a fine sandpaper (2400) (b) cleaning of the carbon particles with absorbent paper (c) Chemical cleaning with HCl 0.1 for
10 min and (d) Rinsing with abundant distilled water.
sulting in areas with maximum heights from the electrode sur-
The SEM micrograph (Fig. 4) of the modified graphite electrode
after 10 min of electrolysis (−1.45 V) of compound 1d in hydroal-
coholic media confirmed the morphology observed by AFM (Fig. 3)
with the RVC electrode, where it can be observed that the de-
posit does not grow uniformly, and there are areas without de-
posited material. Also, the difference of the deposit brightness can
be explained in terms of the different composition and conductiv-
ity of the polymeric material, as was determined by the phase im-
ages in AFM. EDS experiment (Figs. S7,S8) gave information about
the chemical composition of the deposits. When halogenated start-
ing materials were electrolyzed (1d and 1e) on the graphite elec-
trodes, EDS showed that oxygen and halogen content increases
substantially in the passivated electrode surface (Table 2). From
this change of composition is possible to confirm that the poly-
face to the top of material of Z = 1.07 μm and regions without
deposit. The organic matter deposit was confirmed by the corre-
sponding AFM phase mode images, where the deposit has 6.48
times less hardness than those corresponding to the electrode. For
the fully passivated electrode the entire surface morphology be-
comes completely rough (RMS= 349.1 nm) due to the total cover-
age by the polymeric deposit. No longer isolated groups of globular
agglomerates and the surface present a more homogeneous distri-
bution (Z = 385 nm). The phase images showed polymeric regions
with density slightly different from each other, which is proba-
bly due to different polymerization pathways. The full character-
ization of these materials is out of the synthetic objectives of this
study.
8

E.E. López-López, S.J. López-Jiménez, J. Barroso-Flores et al.
Electrochimica Acta 380 (2021) 138239
Table 3
Electrochemical data of S-phenacyl-xanthate derivatives in acetonitrile TBAPF6 0.1 M, V vs Fc/Fc+ using vitreous carbon
electrode and compounds obtained from electrolysis.
meric material deposited during electrolysis on the carbon surface
electrode is produced during the reduction of these compounds in
hydroalcoholic medium.
3.2. Electrochemical behavior of phenacyl xanthate derivatives in
acetonitrile media
It is well known that radicals can react with carbon surfaces
like those obtained by the phenyldiazonium salts reduction [42],
where passive layers are obtained on the electrode surface. How-
ever, differently from the methodology where monolayers are ob-
tained, here the propagation chain generate a thick polymeric de-
posit (Z = 1.07 μm), probably by the reaction of the generated
radicals with the deposited product. Literature indicates the pos-
sibility of using acetophenone derivatives to initiate photochem-
ical polymerization reactions where a radical pathway generates
the polymeric material [43]. In our case, the polymer is observed
with xanthates substituted with halogen groups in 4-position and
with the unsubstituted derivative, probably because of the pos-
sibility of the Ar-X and the Ar-H bonds to react with radicals.
Polymeric materials were reported in the early studies of electro-
chemical reduction of acetophenones by Leone and Elving [44] in
aqueous media and was attributed to side reactions of the radical
intermediates.
In order to determine the possibility of favoring the dimeriza-
tion route to obtain the 1,4-dicarbonyl compounds from the ex-
pected phenacyl radical intermediate in a non-aqueous solvent, it
was decided to use anhydrous ACN as solvent instead of DMF as
reported previously by Matthew [18]. In terms of toxicity an in-
dustrial choice, ACN is preferred in large scale chemical processes
instead of DMF [45,46]. Table 3 summarizes the electrochemical
behavior of compounds 1a, 1c and 1d chosen by their different
electron density in the phenyl ring. The first remarkable feature
of the phenacyl-xanthates is the apparition of a broad oxidation
peak (Fig. 5), this wave was expected because it is well known
the oxidative activation of xanthates by peroxides and other chem-
ical oxidants [47]. This signal founds in the range 1.1 to 1.6 V vs
Fc/Fc+ and appears as an irreversible broad peak nearby the media
discharge; with some compounds it possible to distinguish that at
least two electron-transfer processes are occurring at these poten-
tial values, which explains the signal wide. On the cathodic side,
the two peaks observable in hydroalcoholic media are shifted to
negative values the first at −2.0 to −2.1 V and the second at −2.4
to −2.6 V vs Fc/Fc+; the first shows as an irreversible peak and the
second as a quasi-reversible peak typical for the acetophenones re-
duction in anhydrous media [48].
This information gives us a clear picture of the reactivity in
aqueous media (Scheme 2). After a first electron transfer to the
xanthate derivative 1. the phenacyl radical is produced with cleav-
age of the xantogenate anion, a second rapid electron transfer fol-
lowed by protonation produces the acetophenone 2. In some cases
(X=halogen or H) the obtained compound is further reduced, and
the radical species generated provoke the polymerization of mate-
rial on the electrode.
The electrochemical reduction using 2.2 F/mol of the phenacyl
xanthate derivatives 1a, 1c and 1d gave the expected dimeric com-
pound 3 in low yields (7%–15%), but the major compound is again
the acetophenone 2c, which is obtained in ca. 50% yield in the
three studied compounds. These results are in agreement with the
9

E.E. López-López, S.J. López-Jiménez, J. Barroso-Flores et al.
Electrochimica Acta 380 (2021) 138239
Scheme 3. Proposed mechanism for electrooxidation of S-phenacyl-xanthate 1c in acetonitrile anhydrous on RVC electrode to produce via pathway (A) compound 4c and
pathway (B) compound 5c.
reaction previously reported using Hg/DMF/LiClO4 system where
similar yields for this reaction were reported [18]. When 1 F/mol is
used more than 50% of the starting material is recovered indicating
that dimerization of the phenacyl radical is limited by secondary
reactions as overreduction to the α-carbonyl anion or the hydro-
gen atom abstraction form the S-phenacyl xanthate (1, Scheme 2).
This last pathway was observed during the photochemical reaction
of these compounds [35] where the same radical intermediate is
proposed as the compound that originates both products isolated
here. Considering the obtained compounds, it can be concluded
that protonation remains as the principal reaction for the electro-
chemical generated carbanion, due to the proton donor capability
of ACN. The reaction in other solvents with worse proton donor ca-
pability like DMF might increase the dimer production as has been
observed in the bromobenzene reduction in the presence of CO2
[49].
compound 1c compounds 4c and 5c were isolated in low yield
(Table 3). The proposed mechanism to obtain these compounds is
depicted in Scheme 3. Compound 4c can be obtained from the SET
of the staring material to the anode producing the radical cation
(Scheme 3, pathway A), which react with the carbonyl free electron
pairs to generate the S-O bond, after losing ethylene the benzylic
radical is obtained. A second electron transfer gives the benzylic
cation, whose proton elimination give rise to the observed com-
pound. On the other hand, an internal rearrangement of the start-
ing material to produce compound 5c (S,S-dialkyl-dithiocarbonate)
happened (Scheme 3, pathway B). This reaction can be hypothe-
sized to occur via the corresponding radical cation in a catalytic
cycle were compound 5c can be electroactive (pathway B1) or as
has been proposed in the literature [50] by means of a strong ad-
sorption of the xanthates on the anode (pathway B2) facilitated
by the quaternary ammonium salts present in the anhydrous me-
dia. It is clear from our results that radical cation of compounds
1 has a complex route of reaction in anhydrous medium. Further-
more, the compound 5c may follow a second oxidation that trig-
On the other hand, when compounds 1 were submitted to
anodic reaction in ACN anhydrous, a complex crude of reaction
was obtained in the three cases studied. From the electrolysis of
10

E.E. López-López, S.J. López-Jiménez, J. Barroso-Flores et al.
Electrochimica Acta 380 (2021) 138239
Fig. 6. Energy profile (top) and free energy profile change (bottom) during the electroreduction of phenacyl-xanthate derivatives.
11

E.E. López-López, S.J. López-Jiménez, J. Barroso-Flores et al.
Electrochimica Acta 380 (2021) 138239
Table 4
HOMO and LUMO of S-phenacyl-xanthate derivatives 1a, 1b and 1c determined using a B3LYP/6-31G(d,p) theory level.
Neutral Molecule
HOMO
LUMO
1a R=OMe
E = -6.06 eV
-1.52 eV
1c R=H
1d R=F
= -6.17 eV
-1.79 eV
-1.82 eV
-6.23 eV
gers its decomposition, which would explain the complex anodic
signal observed in the anodic response in cyclic voltammetry. In
the presence of water (10%) this specie reacts rapidly to obtain S-
alkyl-thiocarbonate species in good yields (90–97%) [17].
xantogenate anion it concentrates over the aromatic ketone moi-
ety (Table 5).
The reductive mechanism proposed in Scheme 2 was verified
computing stepwise the relative energy profile for the (a) the SET
step starting from the S-phenacyl xanthate, b) cleavage step of the
radical anion intermediate which generate the phenacyl radicals.
Again, compounds 1a (R=MeO), 1b (R = H) and 1c (R = F) where
selected as representative examples. This energy profile (top Fig. 6)
shows that homolytic dissociation at the C–S bond is a sponta-
neous barrierless process with all these compounds, which is why
the energy of the TS is lower in energy than the starting materials,
and seems to be slightly favored by the presence of electron donor
group. Fig. 6 (bottom) shows the change in Free Energy for the re-
duction process from compounds 1 to the radical anion and then
the cleavage of the C–S bond which produces the phenacyl radical.
It is observed that the ꢀꢀG value associated to the reduction pro-
cess is similar for X = H and F (ca. 5 kcal/mol), whereas it is con-
siderably larger for X = OMe (ca. 10 kcal/mol). These results im-
ply that electrochemical SET of compounds 1 is not a spontaneous
process, but the cleavage of the xantogenate anion from the rad-
ical anion species with simultaneous production of the phenacyl
radical is it.
3.3. Theoretical calculations about the reduction and oxidation
process of S-phenacyl xanthates
HOMO and LUMO of S-phenacyl-xanthate derivatives 1a, 1c and
1d where calculated using B3LYP/6–31G(d,p) theory level (Table 4).
LUMO energy levels of the different starting compounds are lo-
cated almost at the same energy, even if the phenyl ring bears an
electrondonating (MeO) or electronwithdrawing (F) group. This re-
sult is in good agreement with the reduction potential values of
the starting compounds (Tables 1 and 3), where the values are nor
very different among the different compounds studied nor in hy-
droalcoholic or anhydrous media. LUMO is located over the phenyl-
ketone system and the first electron must enter in this region pro-
ducing the radical anion at the carbonyl group (Scheme 2); fur-
ther electron delocalization provokes xantogenate anion elimina-
tion and the appearance of the phenylacyl radical. Additional sup-
port of the first reductive step was obtained by the orbital dis-
tribution calculus for the unpaired electron in the radical anion
species through the spin density plots (Table 5). For all systems
under consideration, the radical anion of the S-phenacyl xanthate
exhibit large delocalization over the conjugated π orbitals system,
which accounts for their observed stability, but upon the loss of
From the HOMO distribution shown in Table 4 also its possible
to support that the oxidation process observed in ACN occurs in
first place on the xanthate moiety as proposed in Scheme 3 and
by Bohn et al. [17]. After the electron rearrangements depicted
in this Scheme it is possible to generate compounds 4c and
5c.
12

E.E. López-López, S.J. López-Jiménez, J. Barroso-Flores et al.
Electrochimica Acta 380 (2021) 138239
Table 5
Spin distribution plots of the proposed intermediates during the electroreduction of phenacyl-xanthate derivatives determined
using a B3LYP/6-31G(d,p) theory level.
Neutral Molecule
Radical anion spin distribution
Phenacyl radical spin
distribution
1a R=OMe
1c R=H
1d R=F
4. Conclusions
G. L.-T.; Supervision, B.A.F.-U. and L.D.M.; Writing—original draft
preparation, E.E.L.-L., S.J.L.-J., E.R-C.; Writing—Review and Editing,
E.R-C., B.A.F.-U. and L.D.M.; Project administration, B.A.F.-U.; fund-
ing acquisition, B.A.F.-U. and L.D.M.
Cyclic voltammetry at vitreous carbon electrode of a series of S-
phenacyl-O-ethyl-xanthates in hydroalcoholic (MeOH/H2O 4:1) and
non-aqueous media (ACNanh/TBAPF6) showed in the first media
only two cathodic waves, whereas in ACNanh one anodic and two
cathodic waves were present. Based on theoretical calculations, the
first cathodic wave was assigned to the reduction of the phenylke-
tone group and the first anodic wave to the xanthate. With some
compounds in hydroalcoholic media and using carbon electrodes,
the reductive reaction produced acetophenone derivatives in high
yield, but with those containing H or halogen atom at the phenyl
ring, polymeric material was deposited on the electrode imped-
ing to compete the reaction. This deposit was characterized by
AFM and SEM-EDS demonstrating the polymerization of the ace-
tophenone radical intermediates was obtained. The electroreduc-
tion on Ti gave in hydroalcoholic media the corresponding ace-
tophenones (>95%) with all the studied compounds. On the other
hand, electrochemical reduction in ACNahn produced small quan-
tities of the dimeric 1,4-dicarbonyl compound PhCOCH2CH2COPh
(7–15%) as well as the corresponding acetophenones (ca 50%). The
radical cation obtained from the oxidation reaction showed to fol-
low a very complicated route of reactions, producing complex mix-
tures with little synthetic value. The reaction mechanism for the
reduction and the homolytic dissociation into the phenacyl radical
were supported by DFT calculations.
Declaration of Competing Interest
The authors declare that they have no known competing finan-
cial interests or personal relationships that could have appeared to
influence the work reported in this paper.
Acknowledgments
BAF-U is grateful by the financial support from PAPIIT-UNAM
No IN208919 and CONACYT Mexico A1-S-18230 projects. EELL and
SJLL thank to CONACYT-Mexico for their MSc scholarships. Nieves
Zavala Segovia, Citlalit Martinez Soto, Uvaldo Hernandez, Alejandra
Nuñez and Lizbeth Triana Cruz are recognized by their technical
support in this work. JB-F acknowledges DGTIC-UNAM for granting
access to the ‘Miztli’ computing framework.
Supplementary materials
Supplementary material associated with this article can be
found, in the online version, at doi:10.1016/j.electacta.2021.138239.
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