One-pot anodic thiocyanation and isothiocyanation of alkenes

Article abstract of DOI:10.1016/j.electacta.2015.07.127

The one-pot anodic thiocyanation and isothiocyanation of alkenes in both acidic two-phase (water-dichloromethane) and homogeneous one-phase (water-acetonitrile) media has been studied. Optimisation experiments on tetramethylethylene as a model alkene invo

Full text of DOI:10.1016/j.electacta.2015.07.127

Accepted Manuscript
Title: One-pot anodic thiocyanation and isothiocyanation of
alkenes
Author: Avishai Levy James Y. Becker
PII:
S0013-4686(15)30194-8
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.electacta.2015.07.127
EA 25409
To appear in:
Electrochimica Acta
Received date:
Revised date:
Accepted date:
12-6-2015
19-7-2015
22-7-2015
Please cite this article as: A. Levy, J.Y. Becker, One-pot anodic
thiocyanation and isothiocyanation of alkenes, Electrochimica Acta (2015),
http://dx.doi.org/10.1016/j.electacta.2015.07.127
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*Revised Manuscript (including Abstract)
One-pot anodic thiocyanation and isothiocyanation of alkenes
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Avishai Levy and James Y. Becker*
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Department of Chemistry, Ben-Gurion University of the Negev, Beer Sheva 84105
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Abstract
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The one-pot anodic thiocyanation and isothiocyanation of alkenes in both acidic two-
phase (water-dichloromethane) and homogeneous one-phase (water-acetonitrile) media has
been studied. Optimisation experiments on tetramethylethylene as a model alkene involved
the use of different acids, anodes, current densities, charge consumption and electrolysis
methods were conducted. In the two-phase medium mainly two addition products (in
moderate yields) of SCN/NCS (major) and two SCN/SCN groups were formed. Other alkyl
substituted alkenes also yielded similar addition products but those involving two SCN groups
became the major ones. In addition, also allylic thiocyanato and isothiocyanato substitution
products were observed. Activated alkenes such as, styrene, indene and butylvinyl ether did
not yield addition products, whereas 1,1-diphenyl-ethylene and 2,3-dimethylfuran gave
substitution products exclusively.
Under homogeneous one-phase aqueous-acetonitrile medium the formation of
SCN/OH adducts became prominent in all cases, including those of styrene and indene. Also
they all afforded the corresponding SCN/SCN and SCN/NCS addition products. However 1,1-
diphenylethylene gave a sole vinylic substitution product whereas 2,3-dimethylfuran did not
react.
Keywords: Anodic thiocyanation/ isothiocyanation of alkenes; Allylic
thiocyanation/isothiocyanation; Vinylic thiocyanation; Constant current electrolysis
* Corresponding author: Telefax +972-8-6461197; Email: becker@bgu.ac.il (J.Y. Becker)
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1. Introduction
Organic compounds bearing thiocyano (R-S-C≡N) or isothiocyano (R-N=C=S) groups
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serve as useful precursors for other functionalised compounds with groups containing the
sulphur atom (e.g., thiols, thio-ethers, organic sulphuric acids) [1] and heterocycles [2]. They
are also applicable as preservatives [2], insecticides [3] and dyes [4, 5].
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A common reagent for thiocyanation is thiocyanogen, (SCN)2, a pseudo-halogen that
exhibits halogen properties, and is highly unstable in aqueous media [6]. Anodic oxidation of
SCN- to its radical is usually followed by dimerisation to produce thiocyanogen (in anhydrous
methanol or acetic acid), or polymerisation to form parathiocyanogen, (SCN)n (in neutral
organic media) [7]. The formation of the latter is diminished considerably in the presence of
acid source [8].
Previous publications described the electrochemical thiocyanation of aromatic compounds
via both one- [8-10] and two-phase [11, 12] electrolysis. However thiocyanation of alkenes
was reported only in a one-phase electrolysis [13, 14]. It was claimed that when acetonitrile is
used, mainly two isomers are formed: a vicinal addition of two thiocyanato groups, and
thiocyanato and isothiocyanato ones[13]. Unfortunately, the reported results in term of yields
and characterisation of isomers were irreproducible neither by us nor by Klein [14]. Klein also
reported [14] that reaction of styrene with electro-generated thiocyanogen in methanol does
not take place unless it is irradiated during electrolysis, to form two isomers: addition of two-
thiocyanato groups and addition of thiocyanato and methoxy groups (yields were not
reported). Interestingly no photo-initiation was required when the reaction was carried out in
acidic medium (methanol-HCl or just glacial acetic acid). Again isolated yields were not
reported but current yields were specified only for selected examples in glacial acetic acid.
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The major theme of the present work has been to perform one-pot electrolysis and study
the effect of acidity and anode material in both heterogeneous two-phase (H2O-
dichloromethane) and homogeneous aqueous-acetonitrile electrolyses on the yields and
selectivity of products generated from thiocyanation of various alkenes.
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2. Experimental
2.1. General
Chemical reagents, reactants and solvents were purchased from commercial suppliers
(Sigma Aldrich, Merck, Biolab, Frutarom and Gadot), and used without further purification.
Constant current electrolyses (CCE) were conducted by Princeton Applied Research
Potentiostat/Galvanostat model 173A in an undivided cells (flasks of 4.5 cm or 3.0 cm in
diameter) using e.g., a Pt foil as the anode (area of 5 cm2) and a carbon rod (6 mm in
diameter) as the cathode (or anode too).
Controlled potential electrolyses (CPE) were conducted by the same instrument in H-
type divided cell (2.5 cm in diameter of each compartment) equipped with a medium glass frit
membrane separating the two compartments, and a Pt foil as the anode (area of 2.4 cm2),
carbon rod (6 mm in diameter, 150 mm in length) as the counter electrode, and Ag wire as a
quasi-reference electrode.
Cyclic voltammetry of NH4SCN in acidic aqueous medium (0.5 N H2SO4) was
conducted by CHI model 730C in a conventional three-electrode cell with Pt disk (1 mm in
diameter) as the working electrode, Ag/AgCl (in 3M NaCl) as the reference electrode, and a
Pt cylindrical gauze (or wire) as the auxiliary electrode.
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The following substrates were investigated for electrolysis: tetramethylethylene
(TME), 1-methylcyclohexene, 2,3-dimethy-1-butene, styrene, 1,1-diphenylethylene, indene,
2,3-dimethy-furan, butylvinyl ether, allyl bromide and trans-stilbene.
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2.2. A procedure for two-phase electrolysis at constant current (CCE)
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An alkene substrate (1.15 mmol) was dissolved in 10 ml dichloromethane (DCM) and
added to 10 ml 0.5 N H2SO4 (in double-distilled water, DDW) solution in an undivided cell (3
cm in diameter). The stirred mixture of the two solvents was immersed in an ice bath and
electrolysed by a set of a Pt working electrode and carbon rod as a counter electrode that were
attached together (but with no physical contact between them) by a Teflon strip. The current
density was 30 mA cm-2, and the electrolysis was terminated after a charge consumption of
4F/mol (460 Coul). Then the two phases were separated, and the aqueous phase was washed
with DCM and combined with the organic phase. The reaction mixture was stirred overnight
at room temperature for the completion of the reaction. Crude products were washed with 50
ml of water, dried over magnesium sulphate powder, and filtered. The products were
separated by preparative silica gel plate, using solvent mixtures of 20% ethyl acetate or
acetone in hexane.
2.3. A procedure for one-phase electrolysis by constant current (CCE)
The same conditions were used as described in the previous section except for replacing
the DCM with acetonitrile. After completion of the electrolysis, the organic solvent and all
organic-soluble reactants and products were extracted by diethyl ether, the aqueous phase was
washed with three portions of diethyl ether, and all organic portions were combined together.
2.4. A procedure for two-phase electrolysis by controlled potential electrolysis (CPE)
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The same conditions were used as described in section 2.2 except that the electrolysis was
conducted in a divided cell by controlling the potential at 1.0 V (vs. Ag wire, which
corresponds to ≈1.2 V vs. Ag|AgCl) and the anode compartment contained 1.15 mmol of an
alkene substrate dissolved in 10 ml dichloromethane (DCM), and 10 ml 0.5 N H2SO4 (in
DDW) solution. Initial current was typically 0.3 A, and the final one was about 30 mA (after a
charge consumption of 4F/mol).
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2.5. Estimation of yields
Six solutions of phenylisothiocyanate of different concentrations (0.01, 0.02, 0.05, 0.1,
0.20 and 0.30 mol dm-3) were prepared by dissolving the appropriate amount in DCM. From
each solution, 2μL of sample was injected into a DB-5 (50m∙0.4580 mm, 1.27 micron film)
column of a TCD-GC (Agilent 6820) under the same method and flow rates. All the areas of
the peaks in the chromatograms were recorded and presented by the "Clarity" software, and
integrated and gathered into MS-Excel 2013 software. A linear curve of integrated areas
versus solution concentration was generated. The curve was forced to the point of (0,0) with
the acceptance that when phenylisothiocyanate is not present, there should be no response.
After completion of electrolysis and removing of the solvents by evaporation, the crude
mixture was dissolved in exactly 10 mL of DCM. Then 2μL of the crude were injected into
the GC column and the integrated area for each peak signifying a product was assigned to the
equation generated by the calibration of phenylisothiocyanate.
2.6. Characterisation of products
2,3-Dimethyl-2-isothiocyanato-3-thiocyanatobutane (1) [15]. IR: a sharp peak of
thiocyanate group at 2152 cm-1, a broad peak of isothicoyanate group at 2067 cm-1; 1H-NMR
(in CDCl3, 400MHz): δ=1.57 (s, 6H), δ=1.61 (s, 6H); 13C-NMR (in CDCl3, 400MHz):
δ=25.57, 26.11, 61.74, 67.69, 111.25, 136.18 ; GC-MS (m/z) (%): 200 (M+), 142, 100 (100),
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83, 69, 55, 41 ; MS (MALDI-TOF): m/z calc. for C8H12N2S2+H+: 201.0515 and
C8H12N2S2+Na+: 223.0334; found 201.0515 and 223.0335, respectively.
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2,3-Dimethyl-2,3-dithiocyanatobutane (2) [15]. IR: a sharp peak of thiocyanate group at
2152 cm-1; 1H-NMR (in CDCl3, 400MHz): δ=1.76 (s, 12H); 13C-NMR (in CDCl3, 400MHz):
δ=26.66, 63.09, 111.04; GC-MS (m/z) (%): 200 (M+), 142, 100, 83 (100), 69, 55, 41 ; MS
(MALDI-TOF): m/z calc. for C8H12N2S2+H+: 201.0515 and C8H12N2S2+Na+: 223.0334; found
201.0515 and 223.0335, respectively.
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2,3-Dimethyl-3-thiocyanatobutan-2-ol (3). IR: a sharp peak of thiocyanate group at
2152 cm-1, a broad peak of hydroxyl group at 3452 cm-1; 1H-NMR (in CDCl3, 400MHz):
δ=1.38 (s, 6H), δ=1.61 (s, 6H); 13C-NMR (in CDCl3, 400MHz): δ=25.85, 26.07, 64.86, 75.65,
113.12; GC-MS (m/z) (%): 159 (M+), 116, 101, 83, 74 (100), 59, 41; MS (MALDI-TOF): m/z
calc. for C7H13NSO+H+: 160.0791, found 160.0791.
2,3-Dimethyl-2-thiocyanatobutane (4). GC-MS (m/z) (%): 142 (M+), 140, 92, 83 (100),
67, 55, 41; MS (MALDI-TOF): m/z calc. for C7H13NS+H+: 144.0841, found 144.0841.
2,3-Dimethylbut-2-en-1-ol (5) [16]. GC-MS (m/z) (%): 100 (M+), 92, 83 (100), 67, 55,
41; MS (MALDI-TOF): m/z calc. for C6H12O+H+: 101.0961, found 101.0960.
2,3-Dimethyl-1,2-dithiocyanatobutane (6). IR: a sharp peak of thiocyanate group at
2152 cm-1; 1H-NMR (in CDCl3, 400MHz): δ=1.09 (d, J=8Hz, 3H), δ=1.12 (d, J=8Hz, 3H)
(two diastereotopic methyl groups), δ=1.58 (s, 3H), δ=2.25 (septet, J= 8Hz, 1H), δ=3.54 (dd,
J= 40Hz, J=16Hz, 2H); 13C-NMR (in CDCl3, 400MHz): δ=17.77, 18.33, 21.94, 35.06, 44.78,
62.72, 110.07, 111.73; GC-MS (m/z) (%): 200 (M+), 142, 100, 83 (100), 69, 55, 41; MS
(MALDI-TOF): m/z calc. for C8H12N2S2+Na+: 223.0334, found 223.0335.
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2-Isothiocyanato-2,3-dimethyl-1-thiocyanatobutane (7). IR: a sharp peak of thiocyanate
group at 2152 cm-1, a broad peak of isothicyanate group at 2079 cm-1; 1H-NMR (in CDCl3,
400MHz): δ=1.03 (d, J=8Hz, 3H), δ=1.075 (d, J=4Hz, 3H) (two diastereotopic methyl
groups), δ=1.50 (s, 3H), δ=2.07 (septet, J= 8Hz, 1H), δ=3.24 (dd, J= 52Hz, J=12Hz, 2H);
13C-NMR (in CDCl3, 400MHz): δ=17.56, 17.68, 22.84, 37.18, 43.85, 67.48, 111.95, 135.71;
GC-MS (m/z) (%): 200 (M+), 158, 142, 128 (100), 98, 83, 69, 55, 41; MS (MALDI-TOF):
m/z calc. for C8H12N2S2+Na+: 223.0334, found 223.0335.
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3-Methyl-2-(thiocyanatomethyl)but-1-ene (8). IR: a sharp peak of thiocyanate group at
2102 cm-1; 1H-NMR (in CDCl3, 500MHz): δ=1.07 (s, 3H), δ=1.09 (s, 3H), δ=2.32 (septet, J=
10Hz, 1H), δ=4.12 (s, 2H), δ=5.035 (dd, J= 12.5Hz, J=5Hz, 2H); 13C-NMR (in CDCl3,
500MHz): δ=21.55, 31.65, 48.65, 110.43, 148.21; GC-MS (m/z) (%): 141 (M+), 126, 113, 99,
82, 67, 55 (100), 41; MS (MALDI-TOF): m/z calc. for C7H11NS+H+: 142.0685, found
142.0685.
2,3-Dimethyl-1-thiocyanatobutan-2-ol (9). IR: a sharp peak of thiocyanate group at
2156 cm-1, a broad peak of hydroxyl group at 3463 cm-1; 1H-NMR (in CDCl3, 400MHz):
δ=0.945 (d, J=4Hz, 3H), δ=0.99 (d, J=8Hz, 3H) (two diastereotopic methyl groups), δ=1.27
(s, 3H), δ=1.89 (septet, J= 8Hz, 1H), δ=3.20(dd, J= 54Hz, J=12Hz, 2H); 13C-NMR (in
CDCl3, 400MHz): δ=16.99, 17.75, 21.98, 36.84, 45.45, 74.70, 113.62; GC-MS (m/z) (%): 159
(M+), 116, 87 (100), 69, 57, 43.
1-Methyl-1,2-dithiocyanatocyclohexane (one diastereoisomer) (10) [17]. IR: a sharp
peak of thiocyanate group at 2156 cm-1; 1H-NMR (in CDCl3, 400MHz): δ=1.57 (s, 3H),
δ=1.47-2.37 (m, 8H, ring protons), δ=3.60 (dd, J= 12Hz, J=4Hz, 1H); 13C-NMR (in CDCl3,
400MHz): δ=20.35, 22.42, 25.17, 31.04, 40.34, 56.12, 59.64, 109.84, 110.55; GC-MS (m/z)
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(%): 212 (M+), 95 (100), 81, 67, 55, 41; MS (MALDI-TOF): m/z calc. for C9H12N2S2+H+:
235.0334 and C9H12N2S2+Na+: 172.0971, found 235.0336 and 172.0971.
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1-Isothiocyanato-1-methyl-2-thiocyanatocyclohexane (one diastereoisomer) (11) [17].
IR: a sharp peak of thiocyanate group at 2156 cm-1, a broad peak of isothiocyanate group at
2057 cm-1; 1H-NMR (in CDCl3, 400MHz): δ=1.57 (s, 3H), δ=1.47-2.26 (m, 8H, ring protons),
δ=3.45 (dd, J= 12Hz, J=4Hz, 1H); 13C-NMR (in CDCl3, 400MHz): δ=21.74, 22.81, 4.27,
30.02, 39.53, 56.69, 64.49, 110.97, 135.84; GC-MS (m/z) (%): 212 (M+), 154, 112, 95 (100),
81, 67, 53, 41; MS (MALDI-TOF): m/z calc. for C9H12N2S2+H+: 235.0334 and
C9H12N2S2+Na+: 172.0971, found 235.0336 and 172.0971.
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6-Isothiocyanato-1-methylcyclohexene (12). IR: a broad peak of isothiocyanate group at
2079 cm-1; 1H-NMR (in CDCl3, 400MHz): δ=1.78 (s, 3H), δ=1.58-2.10 (m, 6H, ring protons),
δ=4.05 (m, 1H), δ=5.61 (m, 1H); 13C-NMR (in CDCl3, 400MHz): δ=18.30, 21.26, 24.96,
30.42, 56.47, 126.96, 130.55, 140.20; GC-MS (m/z) (%): 153 (M+), 95 (100), 79, 67, 55, 39;
MS (MALDI-TOF): m/z calc. for C8H11NS+H+: 154.0685, found 154.0686.
3-Isothiocyanato-1-methylcyclohexene (13). IR: a broad peak of isothiocyanate group at
2086 cm-1; 1H-NMR (in CDCl3, 400MHz): δ=1.70 (s, 3H), δ=1.58-2.10 (m, 6H, ring protons),
δ=4.22 (m, 1H), δ=5.44 (m, 1H); 13C-NMR (in CDCl3, 400MHz): δ=91.21, 23.64, 29.76,
29.76, 53.07, 119.05, 129.92, 130.40; GC-MS (m/z) (%): 152 (M-H)+, 95 (100), 79, 67, 55,
39; MS (MALDI-TOF): m/z calc. for C8H11NS+H+: 154.0685, found 154.0686.
1-(isothiocyanatomethyl)cyclohexene (14). GC-MS (m/z) (%): 153 (M+), 95, 79 (100),
67, 59, 39; MS (MALDI-TOF): m/z calc. for C8H11NS+H+: 154.0685, found 154.0686.
1-Methyl-2-thiocyanatocyclohexanol (one diastereoisomer) (15). IR: a sharp peak of
thiocyanate group at 2152 cm-1, a broad peak of hydroxyl group at 3448 cm-1; 1H-NMR (in
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CDCl3, 400MHz): δ=1.33 (s, 3H), δ=1.41-2.24 (m, 8H, ring protons), δ=3.28 (dd, J= 12Hz,
J=4Hz, 1H); 13C-NMR (in CDCl3, 400MHz): δ=21.86, 23.10, 25.75, 31.34, 40.85, 53.43,
59.21, 73.01, 112.05; GC-MS (m/z) (%): 171 (M+), 156, 144, 128, 111, 97, 86 (100), 71, 55,
43; MS (MALDI-TOF): m/z calc. for C8H13NOS+Na+: 194.0610, found 194.0612.
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1,1-Diphenyl-2-thiocyanatoethene (16) [18]. IR: a sharp peak of thiocyanate group at
2160 cm-1; 1H-NMR (in CDCl3, 500MHz): δ=6.61 (s, 1H), δ=7.19-7.45(m, 10H, ring
protons); 13C-NMR (in CDCl3, 500MHz): δ=111.36, 127.49, 128.77, 129.15, 129.33, 139.35,
148.60; GC-MS (m/z) (%): 237 (M+, 100), 210, 178, 165, 152, 121; MS (MALDI-TOF): m/z
calc. for C15H11NS+Na+: 260.0504, found 260.0507.
5-Isothiocyanato-2,3-dimethylfuran (17). IR: a broad peak of isothiocyanate group at
2027 cm-1; 1H-NMR (in CDCl3, 500MHz): δ=1.90 (s, 3H), δ=2.17 (s, 3H), δ=5.89(s, 1H); 13C-
NMR (in CDCl3, 500MHz): δ=10.01, 11.51, 106.28, 116.03, 133.36, 143.14, 145.66; GC-MS
(m/z) (%): 153 (M+, 100), 138, 124, 110, 95, 67, 43.
2,3-Dimethyl-5-thiocyanatofuran (18). IR: a broad peak of isothiocyanate group at
2167 cm-1; 1H-NMR (in CDCl3, 500MHz): δ=1.94 (s, 3H), δ=2.26 (s, 3H), δ=6.66(s, 1H); 13C-
NMR (in CDCl3, 500MHz): δ=9.83, 11.98, 109.17, 118.05, 125.44, 126.23, 155.22; GC-MS
(m/z) (%): 153 (M+, 100), 138, 127, 120, 110, 99, 83, 67, 43.
1-Phenyl-2-thiocyanatoethanol (19) [19]. IR: a sharp peak of thiocyanate group at 2148
cm-1, a broad peak of hydroxyl group at 3423 cm-1; 1H-NMR (in CDCl3, 500MHz): δ=2.52 (s,
1H, OH), δ=3.185 (dd, J=15, J=10, 1H), δ=3.28 (dd, J= 15Hz, J=5Hz, 1H), δ=5.025 (dd,
J=10, J=5, 1H), δ=7.34-7.43 (m, 5H, ring protons) ; 13C-NMR (in CDCl3, 500MHz): δ=42.13,
72.87, 111.36, 125.97, 129.04, 129.14, 140.81; GC-MS (m/z) (%): 179 (M+), 135, 107 (100),
91, 79, 65, 51, 39; MS (MALDI-TOF): m/z calc. for C9H9NOS+H+ and C9H9NOS+Na+:
180.04776 and 202.02971, found 180.04747 and 202.02948.
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Page 9 of 32

1,2-Dithiocyanatoethylbenzene (20) [15]. IR: a sharp peak of thiocyanate group at 2160
cm-1; 1H-NMR (in CDCl3, 500MHz): δ=3.635(dd, J=15, J=10, 1H), δ=3.785 (dd, J= 10Hz,
J=5Hz, 1H), δ=4.65 (dd, J=10, J=10, 1H), δ=7.37-7.39 (m, 2H, ring protons), δ=7.46-7.47 (m,
3H, ring protons); 13C-NMR (in CDCl3, 500MHz): δ=38.43, 51.67, 109.88, 110.21, 127.71,
129.91, 130.52, 134.24; GC-MS (m/z) (%): 220 (M +), 162 (100), 148, 128, 104, 91, 78, 59;
MS (MALDI-TOF): m/z calc. for C10H8N2S2+H+ and C10H8N2S2+Na+: 221.02017 and
243.00211, found 221.01979 and 243.00166.
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1-Isothiocyanato-2-thiocyanatoethylbenzene (21) [15]. IR: a sharp peak of thiocyanate
group at 2156 cm-1, a broad peak of isothiocyano group at 2058 cm-1; 1H-NMR (in CDCl3,
500MHz): δ=3.27(dd, J=12.5, J=10, 1H), δ=3.37 (dd, J= 15Hz, J=5Hz, 1H), δ=5.135 (dd,
J=10, J=5, 1H), δ=7.35-7.37 (m, 2H, ring protons), δ=7.42-7.46 (m, 3H, ring protons); 13C-
NMR (in CDCl3, 500MHz): δ=41.43, 61.21, 111.83, 126.25, 129.57, 129.74, 136.08, 137.88;
GC-MS (m/z) (%): 220 (M+), 148 (100), 121, 104, 89, 77, 51; MS (MALDI-TOF): m/z calc.
for C10H8N2S2+H+ and C10H8N2S2+Na+: 221.02017 and 243.00211, found 221.01979 and
243.00166.
1-Phenyl-2-thiocyanatoethanone (22) [20]. 1H-NMR (in CDCl3, 400MHz): δ=4.75 (s,
2H), δ=7.30-8.00 (m, 5H, ring protons); GC-MS (m/z) (%): 177 (M+), 105 (100), 77, 51; MS
(MALDI-TOF): m/z calc. for C9H7NOS+H+ and C9H7NOS +Na+: 178.03211 and 200.01406,
found 178.03186 and 200.01381.
1-Thiocyanatovinylbenzene (23) [21]. 1H-NMR (in CDCl3, 400MHz): δ=5.85(dd, J=12,
J=4, 2H), δ=7.24-7.48 (m, 5H, ring protons); GC-MS (m/z) (%): 135 (M-CN)+ (100), 104, 91,
77, 51; MS (MALDI-TOF): m/z calc. for C9H7NOS+H+ and C9H7NOS +Na+: 162.03720 and
184.01914, found 162.03694 and 184.01894.
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Page 10 of 32

2-Thiocyanato-2,3-dihydro-1H-inden-1-ol (24) [22]. IR: a sharp peak of thiocyanate
group at 2156 cm-1, a broad peak of hydroxyl group at 3419 cm-1; 1H-NMR (in CDCl3,
400MHz): δ=2.535 (d, J=4Hz 1H, OH), δ=3.08 (dd, J=16, J=8, 1H), δ=3.515 (dd, J= 16Hz,
J=4Hz, 1H), δ=3.65 (m, 1H), δ=5.31 (t, J= 8Hz, 1H), δ=7.23-7.27 (m, 1H, ring proton),
δ=7.32-7.34 (m, 2H, ring protons), δ=7.41-7.43 (m, 1H, ring proton); 13C-NMR (in CDCl3,
400MHz): δ=37.03, 54.15,81.13, 110.96, 124.35, 124.84, 128.12, 129.47, 138.70, 141.65;
GC-MS (m/z) (%): 191 (M+), 173, 164, 147, 132 (100), 115, 104, 91, 77, 63, 51, 39; MS
(MALDI-TOF): m/z calc. for C10H9NOS+Na+: 214.02971, found 214.03142.
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1,2-Dithiocyanato-2,3-dihydro-1H-indene (25) [15]. IR: a sharp peak of thiocyanate
group at 2160 cm-1; 1H-NMR (in CDCl3, 500MHz): δ=3.185 (dd, J=20, J=5, 1H), δ=3.775
(dd, J= 20Hz, J=5Hz, 1H), δ=4.95 (m, 1H), δ=4.90 (d, J= 4Hz, 1H), δ=7.30-7.48 (m, 5H, ring
proton); 13C-NMR (in CDCl3, 500MHz): δ=38.02, 53.09, 58.45, 109.69, 109.82, 125.47,
125.70, 128.58, 130.75, 135.95, 139.71; GC-MS (m/z) (%): 174 (M-SCN)+, 115 (100), 89, 63;
MS (MALDI-TOF): m/z calc. for C11H8N2S2+Na+: 255.00211, found 255.00407.
3-Isothiocyanato-2-thiocyanato-1H-indene (26) [15]. IR: a sharp peak of thiocyanate
group at 2160 cm-1, a broad peak of isothiocyanato group at 2051 cm-1; 1H-NMR (in CDCl3,
500MHz): δ=3.18 (dd, J=20, J=5, 1H), δ=3.535 (dd, J= 15Hz, J=10Hz, 1H), δ=3.82 (m, 1H),
δ=5.34 (d, J= 10Hz, 1H), δ=7.26-7.28 (m, 1H, ring proton), δ=7.36-7.38 (m, 2H, ring
protons), δ=7.43-7.45 (m, 1H, ring proton); 13C-NMR (in CDCl3, 500MHz): δ=37.31, 52.68,
66.29, 109.59, 124.14, 125.08, 128.58, 130.03, 138.00, 138.22; GC-MS (m/z) (%): 232 (M+),
174, 147, 115 (100), 89, 63, 39; MS (MALDI-TOF): m/z calc. for C11H8N2S2+Na+:
255.00211, found 255.00407.
3. Results and discussion
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It is well known that alkenes are usually oxidised in the range of 1.5-2V (vs. Ag/AgCl)
[23] and according to the CV measurements, the thiocyanate anion is oxidised in acidic
aqueous medium at approximately ≈1.2V, well below the values that correspond to alkenes.
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5
6
.
7
8
This gap enables the formation of (SCN) or (SCN)2 preferentially.
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3.1. Optimisation experiments
Krishnan and Gurjar investigated [12] thiocyanation of aromatic substrates using a
two-phase electrolysis [DCM-H2O (1:1), 0.5 N H2SO4, 0o C] at a carbon anode . The presence
of organic solvent allows the stabilisation of thiocyanogen and the solubility of the substrates
and products, while still utilising the convenient oxidation of anion in the aqueous phase. As
an initial stage it was decided to adopt the experimental conditions of the above mentioned
work also in the present research for anodic thiocyanation of alkenes. In addition, the effects
of other parameters, namely current density, electricity consumption, nature and strength of
acid, anode material and electrolysis methods have been examined as well.
Tetramethylethylene (2,3-dimethyl-2-butene, TME) was chosen as a model substrate
considering its simple 1H- and 13C-NMR spectra. After workup and chromatography
separation, various addition products and one allylic substitution product were isolated and
characterised, as described in Scheme 1.
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Page 12 of 32

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Scheme 1. Products from thiocyanation of TME
Krishnan and Gurjar [12] did not recommend a preferred value of current density for
the two-phase thiocyanation of aromatics, but only mentioned a wide range of it. Therefore
the effect of different current densities in the range of 5-30 mA cm2 on the outcome of the
anodic oxidation of the model substrate TME was examined. The results presented in Table 1
indicate that there is no significant difference among current densities of 10, 20 and 30 mA
cm2, albeit when a current density of 5 mA cm2 was employed the yields are lower. In terms
of the 'desired' thiocyanated products 1-4, the highest yield is achieved at 30 mA cm2 but with
lower selectivity. Also, the undesired hydroxyallyl by-product 5 was relatively high at the
higher current densities. Finally the 'optimisation' process proceeded at first (Tables 1-4) at a
current density of 10 mA cm2 (with a lesser amount of undesired 5), and later (Tables 5-6), at
30 mA cm2 in order to shorten the electrolysis duration).
Table 1 here
Krishnan and Gurjar [12] also claimed that 4F/mol must be consumed during
electrolysis in order to complete the reaction. In order to support this claim, one reaction
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mixture was sampled after consumption of 2F, 4F and 6F. The respective yields are shown in
1
2
3
Table 2, indicating that the best yield is obtained at a consumption of 4F/mol.
4
5
6
Table 2 here
7
8
9
The next step was to examine the effect of different acids on the progression of the
reaction. The results are presented in Table 3. Clearly, the weaker the acid is the lower the
yields are and the reaction requires a strong acid in order to progress further. The reason for
such observation could stem from a higher extent of polarisation of the S-S bond in the
thiocyanogen imposed by the stronger acid (vide infra, mechanistic Scheme 8). Phosphoric
acid and especially formic acid did not afford satisfactory results. Interestingly, the formation
of the undesired by-product (allylic alcohol 5) increased dramatically when using CF3SO3H
(entry 5) and was roughly doubled upon using trifluoroacetic acid (TFA, entry 3)) compared
to sulphuric, phosphoric and formic acids. In conclusion, sulphuric acid (entry 1) and
trifluoromethanesulphonic acid (entry 5) gave the highest yields of combined 1-4. However,
since trifluoromethanesulphonic acid encourages greatly the formation of the undesired allylic
alcohol 5 (and also requires delicate handling due to its being hazardous), sulphuric acid has
been the acid of choice for further studies.
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Table 3 here
Then several anodes were tested to find the most efficient one. The results are
presented in Table 4. Evidently by using carbon felt or lead dioxide (a coated carbon rod), the
yields were not satisfactory. However with carbon rod, Pt foil and glassy carbon plate as
anodes, the yields increased. Also, on the one hand, carbon rods do not promote the formation
of allylic alcohol 5 as Pt foil and glassy carbon plate do, but on the other hand, the combined
yields of the thiocyanated products 1-4 is the highest when using a Pt foil. In addition, the
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Page 14 of 32

latter anode also showed the highest selectivity for the formation of 1(entry 2). Thus it was
1
2
3
decided to choose Pt as the anode for this reaction.
4
5
6
Table 4 here
7
8
9
Finally, to compare the results of constant current electrolysis used in all experiments
above, controlled potential electrolysis (CPE) was also examined (not shown) for the model
substrate TME. It appears that the formation of the undesired allylic alcohol 5 is much lower
(3%) when applying the CPE technique but at the same time, the combined yield of the
desired thiocyanated products 1-4 becomes lower (46% vs 60%) in comparison to the constant
current technique, indicating that there is no real justification to choose CPE over CCE
technique.
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An interesting observation that stems from all the data collected so far for the
optimisation experiments (Tables 1-4) is the selectivity toward the addition of SCN and NCS
groups to form adduct 1 over the addition of two SCN groups (to form adduct 2). The yield of
adduct 3, resulting from addition of OH and SCN groups, remains almost without change (3-
5%) throughout the optimisation process.
3.2. Anodic thiocyanation of various alkenes under "optimised" conditions in a two-phase
mode
After finding 'optimal' conditions for the model TME (namely, using H2SO4 as the
acid, a Pt anode, a current density of 30 mA cm-2, 0o C, consumption of 4F per mole of
substrate,), the behaviour of different type of alkenes was explored under these conditions.
Yields of products from each substrate under the two-phased reactions are summarised in
Table 5. The types of addition and substitution products from each substrate are described in
Schemes 1-5, where the major product is specified in each case. (By the way, for simplicity,
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Page 15 of 32

Schemes 1-4 also describe the products emerged from a homogeneous aqueous acetonitrile
1
2
3
solutions that will be discussed later).
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6
Table 5 here
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Scheme 2. Products from thiocyanation of 1-methylcyclohexene
Scheme 3. Products from thiocyanation of 2,3-dimethy-1-butene
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Page 16 of 32

1
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8
Scheme 4. Substitution product from 1,1-diphenylethylene
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Scheme 5. Products from thiocyanation of 2,3-dimethyl-furan
It appears that similar addition products to those obtained from TME, as well as
substitution products, were also generated from the non-conjugated alkenes in Schemes 2 and
3. However 1,1-diphenylethylene (Scheme 4) and 2,3-dimethyl-furan (Scheme 5) did not
produce any addition product, but substitution products exclusively. Other activated alkenes,
such as styrene and butylvinyl ether (Table 5) underwent polymerisation. Surprisingly, no
thiocyanated products obtained from indene. Also noteworthy is that no reaction was
observed for inactivated alkenes such as allyl bromide and trans-stilbene. The lack of
reactivity in the latter case could be attributed to the dual character of the phenyl groups
reducing the π-electron density at the reaction centre [24].
3.3. Electro-thiocyanation of various alkenes under "optimised" conditions in a one-phase
mode
In attempts to improve the yield of the thiocyanated products, a shift from a two-phase
medium to a homogeneous one-phase medium (aqueous acetonitrile) was made, leaving
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identical reaction conditions. Despite the enhanced competing polymerisation reaction (to
generate parathiocyanogen) in the homogeneous one-phase electrolysis, thiocyanogen still
reacted with unsaturated substrates. Yields of products from each substrate are summarised in
Table 6, and spectrum of products from each substrate are described in Schemes 2-4 above
and 6-7 below.
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Table 6 here
The comparative results (Tables 5 and 6) indicate that the total adducts yield
improved for the alkyl substituted substrates 1-methylcyclohexene and 2,3-dimethyl-2-butene
in the homogeneous one-phase reaction over the two-phase reaction. However the combined
yields of all thiocyanated products from all substrates reacted under the homogeneous one-
phase reaction never exceeded the 60% obtained from TME under the two-phase medium.
This observation is not surprising because it is well-known that thiocyanogen is apparently a
weak electrophile. Therefore, it is also clear that the reaction is more efficient when alkenes
are more electron-rich (last columns in Tables 5 and 6), with an obvious trend of increased
yield of the three adducts (SCN/NCS, SCN/SCN, OH/SCN) as the number of EDGs
increases, especially under the two-phase conditions.
Interestingly, styrene and indene, that failed to undergo thiocyanation under the
formerly mentioned two-phase conditions (styrene polymerised) became active in the
homogenous water-acetonitrile mixture (Schemes 6 and 7), possibly due to a different
intermediate type involved in the mechanism. In both cases (though more pronounced with
indene) the formation of the thiocyanated hydroxy adducts became prominent.
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Page 18 of 32

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Scheme 6. Products from thiocyanation of styrene
Scheme 7. Products from thiocyanation of indene
The ambident nucleophilic nature of the thiocyanate is revealed by the formation of
two isomers of addition products (one with SCN/SCN and one with SCN/NCS groups). The
selectivity however, varies. Addition of two thiocyanato groups was preferred in both media,
(except for TME).
In addition to the observed addition products, several substitution products were also
formed, notably the allylic hydrogen substitution with iso- or thiocyanato groups formed from
the alkyl substituted alkenes (except for TME), mostly in the two-phase system. However, the
allylic hydroxylated by-product was produced mainly under the homogeneous one-phase
reaction.
3.4. Mechanism
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It is expected that the acid plays the same role as in the electrochemical aromatic
thiocyanation [8], that is hydrogen bonding causing the polarisation of the sulphur atom and
enabling its electrophilic character. Based on the fact that products obtained followed the
Markownikoff's rule, and the known pseudo-halogen properties of thiocyanogen, it is
suggested (Scheme 8) that upon hydrogen bonding and the subsequent electrophilic attack on
the sulphur atom, the mechanism goes through intermediates I (for aliphatic alkenes) or II
(for aromatic alkenes), as suggested for the chemical thiocyanation of alkenes via
thiocyanogen [15, 18, 24, 25]. Upon electrophilic attack, the thiocyanogen undergoes
heterolytic fission and the thiocyanate anion is released. The latter could attack via either the
nitrogen or the sulphur atoms due to its ambident property.
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Scheme 8. Suggested mechanism for the anodic thiocyanation of alkenes
The difference in reactivity between the non-conjugated alkenes studied and the
conjugated ones in both media, as well as the prominence of the formation of thiocyanated
hydroxy adducts mostly in the homogeneous H2O\CH3CN medium can be explained by
solvation effects. It has been claimed [24] that the 'open' cationic intermediate II (Scheme 8)
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(attributed to conjugated alkenes) is solvated more heavily in the homogeneous medium (by
polar molecules of water and acetonitrile) than the bridged carbocation I (attributed to non-
conjugated alkenes). This explains the vast addition of OH group to styrene and indene.
However in the two-phase H2O\DCM medium, it seems reasonable to assume that
intermediate II is unstable since it is less accessible to the aqueous phase and therefore,
cannot be solvated efficiently by water molecules. On the other hand, bridged intermediate I
can be also stabilised and solvated in H2O\DCM, making the aliphatic alkenes reactive in both
media.
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Rationalisation of the formation of allylic iso- or thiocyanates or hydroxylation can be
explained through the radical mechanism demonstrated in Scheme 9 [26, 27], assuming the
source of thiocyanate radicals stems from initial anodic oxidation of SCN- anions.
Scheme 9. Suggested mechanism for the formation of allylic substitution products
Rationalisation of the selectivity between the two addition isomers (SCN/SCN and
SCN/NCS groups) can be explained by both kinetic and steric considerations, as were
described for the chemical thiocyanation of alkenes [15], since the results obtained here well
correlates with those of the chemical process. It is noteworthy that in general the total product
yields in the chemical method are higher than in both one- and two-phase electrolytic systems.
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This could stem from the fact that the chemical reaction involved a two-step process, allowing
the formation of thiocyanogen (in non-aqueous media) prior to the addition of alkenes [15].
Therefore it seems that in the one-pot process the instability of thiocyanogen is greater (due to
the presence of water), leading to lower yields.
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32
33
34
35
36
37
38
39
40
41
42
43
44
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46
47
48
49
50
51
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53
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60
61
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4. Conclusions
An environmentally friendly in-situ electrochemical thiocyanation (that avoids the
use of toxic oxidizing agents) of various alkenes has been investigated under 'optimal
conditions' (presence of a strong acid, current density of at least 10 mA cm2, a Pt anode,
charge consumption of 4F, and at 0o C)). The one-pot thiocyanation was carried out via
either a two-phase process (DCM-water) or one-phase (homogeneous aqueous
acetonitrile), employing the CCE technique, and afforded medium yields of addition and
substitution products. Formation of addition products under the two-phase reaction was
found to be limited to aliphatic substituted alkenes. Aromatic conjugated alkenes reacted
only under homogeneous CH3CN/H2O medium. It is reasonable to assume that the 'open'
carbocation II (Scheme 8) (attributed to styrene and indene) is more stable in the
homogeneous medium, being solvated by both polar water and acetonitrile molecules, than
in the less polar DCM/H2O medium in which water molecules are less accessible. However
the bridged carbocation I (attributed to non-conjugated alkenes) can be stabilized and
solvated also in DCM/H2O, making the aliphatic alkenes reactive in both media.
It was also found that addition of SCN\SCN is favourable over SCN\NCS in most cases
whereas electrolysis in homogeneous aqueous acetonitrile promoted the addition of SCN/OH
groups to alkenes.
22
Page 22 of 32

Acknowledgments
1
2
3
The authors are grateful to Dr. M. Karpasas for HRMS measurements and to Mrs E. Solomon
4
5
for technical assistance.
6
7
8
9
References
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
[1] F. Romanowski, H. Klenk, Thiocyanates and Isothiocyanates, Organic, Ullmann's
Encyclopedia of Industrial Chemistry, 36 (2000) 609-618.
[2] K. Srivastava, S. Purohit, S. Singhal, Studies on nitrogen and sulphur containing
heterocyclic compound: 1,3,4 - thiadiazole, AJBPS 3(21) (2013) 6-23.
[3] D.L. MacKinnon, A.P. Farrell, The effect of 2-(thiocyanomethylthio)benzothiazole on
juvenile coho salmon (Oncorhynchus Kisutch): Sublethal toxicity testing, Environ. Toxicol.
Chem., 11 (1992) 1541-1548.
[4] O. Hideo, J.E. Casida, Glutathione S-transferases liberate hydrogen cyanide from organic
thiocyanates, Biochem. Pharmacol., 20 (1971) 1708-1711.
[5] J. Griffiths, Recent developments in the colour and constitution of organic dyes, Progress
in Coloration and Related Topics, 11 (1981) 37-57.
[6] J.L. Wood, Substitution and addition reactions of thiocyanogen, Organic Reactions, John
Wiley & Sons, 2004.
[7] D.A. Holtzen, A.S. Allen, Kinetic parameters for the anodic oxidation of thiocyanate at
the glassy carbon electrode, Anal. Chim. Acta, 69 (1974) 153-160.
[8] A. Gitkis, J.Y. Becker, A selective one-pot electrochemical thiocyanation of
methoxybenzene (anisole), J. Electroanal. Chem., 593 (2006) 29-33.
[9] A. Gitkis, J.Y. Becker, Anodic thiocyanation of mono- and disubstituted aromatic
compounds, Electrochim. Acta, 55 (2010) 5854-5859.
23
Page 23 of 32

[10] L. Fotouhi, K. Nikoofar, Electrochemical thiocyanation of nitrogen-containing aromatic
and heteroaromatic compounds, Tetrahedron Lett., 54 (2013) 2903-2905.
[11] P. Krishnan, V. Gurjar, A Two phase electrochemical method for thiocyanation, Synth.
Commun., 22 (1992) 2741-2744.
1
2
3
4
5
6
7
8
9
[12] P. Krishnan, V. Gurjar, Electrochemical thiocyanation by two phase electrolysis, J. Appl.
Electrochem., 23 (1993) 268-270.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
[13] G. Cauquis, G. Pierre, Thiocyanation and selenocyanation of olefins by an
electrochemical route, Tetrahedron, 34 (1978) 1475-1479.
[14] W.J. de Klein, Electrochemical synthesis of vicinal dithiocyanates from olefins and a
thiocyanate salt in acidic media, Electrochim. Acta, 18 (1973) 413-416.
[15] R. Bonnett, R.G. Guy, D. Lanigan, Pseudohalogen chemistry- Part IV. Heterolytic
addition of thiocyanogen to alkenes, Phosphorus and Sulfur and the Related Elements, vol. 2
(1976) 95-103 and Tetrahedron 32 (1976) 2439-2444.
[16] H.S. Dang, A.G. Davies, I.G.E. Davison, C.H. Schiesser, Reactivities of some
hydroperoxides toward allylic rearrangement and related reactions, J. Org. Chem., 55 (1990)
1432-1438.
[17] R.C. Cambie, D.S. Larsen, P.S. Rutledge, P.D. Woodgate, Bromothiocyanation of
alkenes, J. Chem. Soc., Perkin Trans. 1, (1981) 58-63.
[18] R.G. Guy, I. Pearson, Pseudohalogen Chemistry. III. Orientation of heterolytic addition
of thioeyanogen chloride to some unsymmetrical alkenes, Bull. Chem. Soc. Jpn., 49 (1976)
2310-2314.
[19] J.S. Yadav, B.V.S. Reddy, C.S. Reddy, Selectfluor™: A novel and efficient reagent for
the synthesis of β-hydroxy thiocyanates, Tetrahedron Lett., 45 (2004) 1291-1293.
[20] S. Lanaspèze, R. Neier, Synthesis of substituted 1-thiocyanatobutadienes and their
application in a Diels-Alder/[3,3] sigmatropic rearrangement tandem reaction, Monatsh.
Chem., 136 (2005) 597-607.
24
Page 24 of 32

[21] M. Giffard, J. Cousseau, L. Gouin, M.R. Crahe, Addition of thiocyanic acid to acetylenic
compounds using mercury(II). I. Addition of the thiocyanate group (SCN-) in the presence of
a strong acid, Tetrahedron, 41 (1985) 801-810.
1
2
3
4
5
6
7
8
9
[22] H. Sharghi, M.A. Nasseri, Schiff-base metal(II) complexes as new catalysts in the
efficient, mild and regioselective conversion of 1,2-epoxyethanes to 2-hydroxyethyl
thiocyanates with ammonium thiocyanate, Bull. Chem. Soc. Jpn., 76 (2003) 137-142.
[23] N.L. Weinberg, H.R. Weinberg, Electrochemical oxidation of organic compounds,
Chem. Rev., 68 (1968) 449-523.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
[24] R.G. Guy, I. Pearson, Pseudohalogen chemistry. Part II. Heterolytic addition of
thiocyanogen chloride to some symmetrical [small alpha]-arylalkenes, J. Chem. Soc. Perkin
Trans. 2 (1973) 1359-1362.
[25] R.G. Guy, I. Pearson, Pseudohalogen chemistry. I. Heterolytic addition of thiocyanogen
chloride to symmetrical alkenes and cycloalkenes, J. Chem. Soc., Perkin Trans. 1, (1973) 281-
284.
[26] R.G. Guy, I. Pearson, Pseudohalogen Chemistry. V. Homolytic addition of thiocyanogen
chloride to some haloalkenes on irradiation with UV light, Bull. Chem. Soc. Jpn., 50 (1977)
541-542.
[27] R.G. Guy, J.J. Thompson, Pseudohalogen chemistry-VI: Homolytic thiocyanation of
mono- and di-substituted alkenes using thiocyanogen and ultraviolet light, Tetrahedron, 34
(1978) 541-546.
25
Page 25 of 32

Table(s)
Table 1. Yields of products from TME at different current densities after consuming
4F/mol (1:1 DCM/H2O-H2SO4 at 0o C, carbon anode)
Current
Total yield Sum of
Entry
density
(mA cm2)
1 (%) 2 (%) 3 (%) 4 (%) 5 (%)
(%)a
1-4 (%)b
1
2
3
4
5
25
33
35
32
10
9
3
3
3
4
1
1
1
3
2
5
8
7
41
51
55
59
39
46
47
52
10
20
30
8
13
a Yields are based on a GC calibration curve made for PhNCS as an external standard
b Combined yields of thiocyanated products
Table 2. Yields* of products 1-4 from TME after consuming 2-6 F/mol at 10 mA cm2
(1:1 DCM/H2O-H2SO4 at 0o C, carbon anode)
Entry Charge consumption 1 (%) 2 (%) 3 (%) 4 (%) Sum of 1-4 (%)
1
2
3
2F
4F
6F
8.5
33
26
4.5
9
2
3
4
1
1
1
16
46
40
9
* Based on a GC calibration curve made for PhNCS as an external standard
Page 26 of 32

Table 3. Yields of products from TME with different acids (at 10 mA/cm2, after
consuming 4F/mol, (1:1 DCM/H2O-H2SO4 at 0o C, carbon anode)
Acid
Total yield Sum of
pKa 1 (%) 2 (%) 3(%) 4 (%) 5 (%)
Entry (0.5N)
(%)a
1-4 (%)
46
1
2
3
4
H2SO4 -3.0b
H3PO4 2.12b 11
33
9
4
9
3
4
3
1
1
1
5
3
51
23
20
TFA
Formic
acid
-0.25
29
10
52
42
3.77
5
1
3
0
3
12
9
5
CF3SO3H -14.0
42
9
4
2
17
74
57
a Yields are based on a GC calibration curve made for PhNCS as an external standard.
b First PKa value
Page 27 of 32

Table 4. Yields of products from TME at different anodes (at 10 mA cm2, after
consuming 4F/mol (1:1 DCM/H2O-H2SO4 at 0o C, carbon anode)
Total
yield (%)a
Sum of 1-4
Entry
1
Anode
1 (%) 2 (%) 3 (%) 4 (%) 5 (%)
(%)
Carbon
rod
33
9
3
1
5
51
46
Platinum
foil
2
3
4
46
7
8
7
9
5
5
5
1
1
1
18
2
78
22
28
60
20
25
C/PbO2
Carbon
felt
10
3
Glassy
Carbon
plate
5
38
6
5
1
12
62
50
a Yield is based on a GC calibration curve made for PhNCS as an external standard.
Page 28 of 32

Table 5. Yields of products from each substrate under 'optimal' two-phase conditions
(in 1:1 DCM/H2O-H2SO4; Pt anode; 30 mA cm-2; 4F/mol; 0o C )
Sum of
thiocyanated
products (%)
Product:
2∙SCN
SCN/NCS SCN/OH Substitution
Other
additiona additiona additiona productsa productsa
Substrate
Tetramethylethylene
2 (8%)
1 (46%)
3 (5%)
-
4 (1%)
60
61
16
-
1-Methylcyclohexene 10 (20%) 11 (1%)
-
-
-
-
-
-
-
13-15 (40%)b
-
-
-
-
-
-
-
2,3-Dimethy-1-butene 6 (8%)
7 (2%)
8 (6%)
Styrenec
-
-
-
-
-
-
-
-
-
-
-
Butylvinyl etherc
1,1-Diphenylethylene
-
16 (21%)
-
-
21
-
Indened
2,3-Dimethy-furan
17-18 (16%)e
16
a Yield is based on a GC calibration curve made for PhNCS as an external standard. The
numbers inside the brackets next to each value indicate the corresponding product.
b Yield distribution: 13 = 16%, 14 = 17%, 15 = 7%.
c Substrates underwent polymerization.
d No products obtained
e Yields of 17 = 9% and 18 = 7%.
Page 29 of 32