Photoredox-Catalyzed Intermolecular Radical Arylthiocyanation/Arylselenocyanation of Alkenes: Access to Aryl-Substituted Alkylthiocyanates/Alkylselenocyanates

Article abstract of DOI:10.1021/acs.joc.8b03155

An efficient and highly selective approach for intermolecular arylthiocyanation/arylselenocyanation of alkenes has been reported under mild conditions. Using diazonium salts as the arylating agent and ammonium thiocyanate as the thiocyanate source, chemos

Full text of DOI:10.1021/acs.joc.8b03155

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Featured Article
Photoredox-Catalyzed Intermolecular Radical Arylthiocyanation/
Arylselenocyanation of Alkenes: Access to Aryl-
Substituted Alkylthiocyanates/ Alkylselenocyanates
Injamam Ul Hoque, Soumyadeep Roy Chowdhury, and Soumitra Maity
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.8b03155 • Publication Date (Web): 21 Jan 2019
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The Journal of Organic Chemistry
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Photoredox-Catalyzed Intermolecular Radical
Arylthiocyanation/Arylselenocyanation of Alkenes: Access to Aryl-
Substituted Alkylthiocyanates/Alkylselenocyanates
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Injamam Ul Hoque, Soumyadeep Roy Chowdhury and Soumitra Maity*
Department of Applied Chemistry, Indian Institute of Technology (ISM) Dhanbad, JH 826004, India.
R2
SCN / SeCN
NH4SCN
or
KSeCN
Ar
R2
ArN2BF4
R1
+
+
R1
R3
PC*
R3
regioselective
38 examples
yields up to 87%
styrenes as well as
acrylates are compatible
ABSTRACT: An efficient and highly selective approach for intermolecular arylthiocyanation/arylselenocyanation of alkenes
has been reported in mild conditions. Using diazonium salts as the arylating agent and ammonium thiocyanate as the
thiocyanate source, chemo-selective difunctionalisation of alkenes has been done under the irradiation of visible light. Both
styrenes and acrylates work well to deliver various aryl-substituted alkylthiocyanates in good to excellent yields. In
addition, hitherto unknown -aryl alkylselenocyanates were also synthesized using the developed protocol with potassium
selenocyanate.
INTRODUCTION
Organic thiocyanates are useful functional motifs
present in various bioactive compounds and natural
products.1 Additionally, they have been widely used as
intermediates in the synthesis of sulfur-containing
heterocycles,2 since thiocyano group could be easily
transformed to other sulfur functional groups.3 For
instance, -aryl substituted -keto thiocyante are used as
intermediates in the synthesis of many thiazoles.4
Therefore, considerable effort has been made on the
development of efficient methods for the incorporation of
thiocyano group into small organic molecules. Traditional
routes to this class of molecules include the nucleophilic
substitution of thiocyanate to alkyl halides5 or alcohols,6
and electrophilic thiocyanation of thiocyanate salts7 or
isothiocyanate anion8 in the presence of oxidant. However,
the major drawback associated with most of them is use of
large excess of strong oxidants, low region- and chemo-
selectivity, as well as limited substrate scope. Thus,
developing new and efficient thiocyanation reactions for
the synthesis of SCN-containg small molecules is still
highly desirable.
have received considerable attention and significant
progress have been made.11 While several examples on the
Meerwein arylation-addition reactions of alkenes,12 such
as
oxyarylation,12a-c
aminoarylation,12d
formyloxyarylation,12e
trifluoromethylthioarylation,12f
haloarylation,12g-h and xanthatoarylation12i-k are known
(Scheme 1a). But similar type of thiocyanoarylation with
13
olefin is limited to some alkenes,
halogenostyrene,13a
compounds,13c and acrylate derivatives13d-e under
like -
,-trifluorostyrene,13b
allylic
Scheme 1. a) Photoredox-catalyzed difunctionalization
of alkens using aryl diazonium salts; b) Working
hypothesis; c) Present protocol of photoredox-
catalyzed arylthiocyanation/arylselenocyanation.
In the past decade, radical difunctionalization of olefins9
has become a unique technique to transform simple
alkenes to functionalised materials as value-added
products. More recently, the visible light mediated single-
electron transfer (SET) process has further matured this
radical difunctionalization strategy in environmentally
benign mild conditions.10 In this context, photoredox-
catalyzed Meerwein arylation using aryl diazonium salts
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a) Previous work
4.
Ru(bpy)3(PF6)2
THF
Dioxane
Toluene
DMF
32
17
1
2
3
4
5
6
7
8
Ar
ArN2BF4
Z
Z
OR [12a]
NHCOR [12a,d]
OCHO [12e]
5.
Ru(bpy)3(PF6)2
Ru(bpy)3(PF6)2
Ru(bpy)3(PF6)2
Ru(bpy)3(PF6)2
Eosin Y
=
=
=
R2
photoredox
catalysis
R2
R1
+
R1
6.
24
(Nucleophile)
Z
7.
0
b) Working hypothesis
R
8.
DMSO
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
0
Ar
R
SET-radical addition
9.
28
protonation
oxygenation
dimerization
H-elimination
NCS
10.
11.
12.
13.d
14.e
15.
16. f
Rose Bengal
Methylene Blue
Rhodamine B
Ru(bpy)3(PF6)2
Ru(bpy)3(PF6)2
-
33
SCN
Ar
(potential
side reactions)
9
18
10
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Ox
[
]
Ar
Ar
R
23
R
R
(key intermediate)
57
c) This work
52
R2
SCN / SeCN
Ar
photoredox catalysis
visible light, rt
NH4SCN
or
KSeCN
trace
trace
ArN2BF4
R1
R2
+
+
R1
R3
Ru(bpy)3(PF6)2
R3
aUnless otherwise noted, all reactions were carried out
with: 1b (0.4 mmol), 2c (0.2 mmol), NH4SCN (0.6 mmol),
photocatalyst (2 mol%), and degassed solvent (2 mL) in a
culture tube under argon at rt irradiated with 12W blue LED
Cu-catalysis. Additionally, these reactions are not
chemoselective and often furnished with by-products. We
envisioned that visible light induced SET-aryl radical
addition followed by oxidative trapping of the carbocation
by thiocyanate nucleophile could render the desired -aryl
alkylthiocyanate (Scheme 1b). But the major challenges
remain the chemo- and region-selective addition of aryl
radical over thiocyanate radical onto the alkene double
bond under the reaction conditions, as both thiocyanate
anion14 and diazonium salts11 are known to generate
radicals under visible light mediated photoredox catalysis.
Secondly, the radical intermediate, which was generated
after aryl radical addition was susceptible to generate
undesired products by oxygenation to -arylketone,15
reduction followed by protonation to aryl alkane,16 or H-
elimination to -aryl alkene.17 So efficient single electron
oxidation of the radical intermediate would selectively
provide the targeted -aryl alkylthiocyanate.
b
c
d
e
for 6 h. yield, in air, KSCN instead of NH4SCN, NaSCN
f
instead of NH4SCN, in dark.
We commenced our investigation with 4-methyl styrene
(1b), 4-methoxybenzenediazonium tetrafluoroborate (2c),
and ammonium thiocyanate to evaluate the optimal
conditions of the three-component reaction under visible
light photoredox catalysis (Table 1).19 Using a blue LED
light, irradiation of a solution of 1b, 2c, and ammonium
thiocyanate in acetonitrile with [Ru(bpy)3(PF6)2] in open
air afforded the desired arylthiocyanation product 3b in
31% yield (Table 1, entry 1). Degassing the reaction
mixture by argon dramatically improved the yield of 3b
from 31% to 76% (entry 2). This is likely due to
suppression of the competitive oxidative side reactions
involving within two components of 2c and thiocyanate
with the styrene in the presence of oxygen from air. 14-15 It
is also worth noting that complete regiocontrol was
observed with respect to styrene in the difunctionalization
event. Use of other common solvents such as DCE, THF,
Dioxane, and Toluene led to lower yields of 3b (entries 3-
6) and no reaction took place in highly polar solvents DMF
or DMSO (entries 7-8).20 Other photocatalysts such as
Eosin Y, Rose Bengal, Methylene Blue, and Rhodamine B
were less effective in this transformation (entries 9-12).
Further investigation revealed that commercially available
other SCN sources such as KSCN and NaSCN could also
afford the desired product 3b, but in lower yields (entries
13 and 14). Finally, control experiments performed
without catalyst or light produced only trace of the
product (entries 15 and 16), thus indicating that both the
catalyst and light were crucial for effective conversion into
3b.
As part of our ongoing work on radical
difunctionalization of olefin,18 we report herein an efficient
photoredox-catalyzed intermolecular arylthiocyanation of
alkenes to deliver vicinal aryl-substituted alkyl
thiocyanates using aryl diazonium salts as the arylating
agent and ammonium thiocyanate as an inexpensive
thiocyanation reagent (Scheme 1c). The method is mild
(visible light, room temperature), operationally simple and
display a broad substrate scope. In addition, -aryl
alkylselenocyanates were also synthesized first time using
the developed protocol with potassium selenocyanate.
RESULTS AND DISSCUSION
Table 1. Optimization of the reaction conditiona
OMe
SCN
N2BF4
condition
NH4SCN
+
+
With the optimized reaction conditions in hand (Table 1,
entry 2), the substrate scope of alkenes in three
component reaction was explored. As shown in scheme 2,
the developed method was found to easily accommodate a
variety of styrenes and acrylates. Styrenes bearing various
substituents on the aromatic ring, including electron-
donating (3b–d) and electron-withdrawing (3e–j) groups,
underwent the desired transformation, affording the
corresponding products in good to excellent yields.
MeO
2c
1b
3b
entry
1.c
Photocatalyst
Ru(bpy)3(PF6)2
Ru(bpy)3(PF6)2
Ru(bpy)3(PF6)2
solvent
CH3CN
CH3CN
DCE
yield (%)b
31
76
51
2.
3.
2
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Interestingly, the position of substituents on the aromatic give the desired product 3o-p with a mixture of
1
2
3
4
5
6
7
8
ring of styrene had little effect on the reaction outcome, as
para-, meta- and ortho-chlorostyrenes gave similar yields
of the corresponding products (3g–i). In addition, the
survival of halogen handle in the products providing
opportunities for further elaboration via traditional cross-
coupling reaction. Orthogonal functionalities, including
ester (3k), benzyl halide (3l) are also well tolerated under
these mild, radical-mediated reaction conditions. The
structure of 3k was unambiguously confirmed by X-ray
diffraction analysis (CCDC 1813182, Figure S4 in SI).21
Pleasingly, vinylarene featuring fused aromatic ring 3m
and heteroatom 3n was found to be well accommodated.
Moreover, internal styrenes were also reacted smoothly to
Scheme 2. Scope of Alkenesa, b
diastereomers. Interestingly the conjugated diene, 1-
phenyl-1,3-butadiene participated in the protocol, which
occurred regioselectively at the terminal double bond to
afford the desired product 3q. Importantly, acrylates also
participated in this reaction uneventfully, generating the
desired products (3r–t) with excellent regioselectivity, but
Meerwin arylation-elimination product 3u was observed
in case of 1-Vinyl-2-pyrrolidinone. Finally we have
attempted
photo-arylthiocyanation
with
aliphatic
9
substrates such as 1-dodecene, norbornene, cyclohexene,
and allylbenzene. These substrates did not react under the
reaction
10
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OMe
SCN
R2
N2BF4
Ru(bpy)3(PF6)2 (2 mol%)
R1
NH4SCN
R2
+
+
OMe
MeO
R1
CH3CN, rt
blue LED
MeO
R3
R3
2c
1a-u
3a-u
OMe
Me
OMe
OMe
OMe
OMe
OMe
SCN
SCN
SCN
SCN
SCN
MeO
MeO
F
3a
, 74%
3b
3c
3d
, 70%
3e
, 82%
, 76%
, 87%
OMe
OMe
Cl
OMe
OMe
SCN
SCN
SCN
SCN
SCN
Br
Cl
Cl
NO2
, 73%
SCN
3f
3g
, 81%
3h
3i
, 77%
, 79%
, 79%
3j
OMe
OMe
SCN
SCN
Cl
AcO
3k
, 84%
3l
, 49%
3m
, 80%
OMe
OMe
OMe
SCN
OMe
SCN
SCN
SCN
Me
F
N
3n
, 44%
3o
, 60%
3p
, 58%
3q
, 42%
OMe
OMe
OMe
OMe
SCN
Me
SCN
SCN
N
MeO2C
tBuO2C
NC
O
3r
3s
, 44%
3u
, 53%
, 64%
3t
, 60%
aUnless otherwise noted, all reactions were carried out with: 1 (0.4 mmol), 2c (0.2 mmol), NH4SCN (0.6 mmol), Ru(bpy)3(PF6)2
b
(2 mol%), and degassed CH3CN (2 mL) in a culture tube under argon at rt irradiated with 12W blue LED for 6 h. yield.
conditions, presumably due to their intrinsic lower
reactivity than aromatic alkenes or acrylates.22
heterocycle 4i also participated in this event to produce
desired product in good yield.
We then explored the reactivity of different diazonium
salts as aryl-group carrier. As shown in Scheme 3,
aryldiazonium salts bearing electron-withdrawing and
electrondonating substituents at the para position of
phenyl ring 4a-e, showed good reactivity. Both ortho-and
meta-substituted aryldiazonium salts 4f–g were suitable
substrates, but the lower reactivity of ortho-substituent
could be due to steric effect. Additionally, di-substituted
aryldiazonium salts 4h was compatible in the present
study. Moreover, aryldiazonium salts containing quinoline
Scheme 3. Scope of aryldiazonium saltsa, b
3
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SCN
SeCN
Ru(bpy)3(PF6)2 (2 mol%)
Ru(bpy)3(PF6)2 (2 mol%)
Ar
Ar
ArN2BF4
NH4SCN
ArN2BF4
KSeCN
+
+
+
+
1
CH3CN, rt
blue LED
CH3CN, rt
R
R
blue LED
tBu
tBu
tBu
tBu
2
3
4
5
6
7
8
9
1v
4a-i
2
1
5a-h
2
CN
NO2
OMe
OMe
Br
OMe
Br
SCN
SCN
SCN
SeCN
SeCN
SeCN
tBu
Ph
tBu
tBu
Cl
4a
, 70%
4b
4c
, 75%
, 57%
5a
, 67%
5b
OMe
5c
, 46%
, 57%
Ph
CF3
SeCN
NO2
SeCN
SCN
SCN
SCN
10
11
12
13
14
15
16
17
18
19
20
21
22
23
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40
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42
43
44
45
46
47
48
49
50
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58
59
60
OMe
tBu
tBu
5d
, 48%
5e
, 59%
4d
4e
, 62%
, 72%
4f
, 38%
OMe
Me
O
SeCN
OMe
OMe
N
SeCN
SeCN
O
O
SCN
SCN
SCN
tBuO2C
PhO2C
O
CF3
5f
O
tBu
tBu
5g
, 34%
5h
, 40%
, 45%
tBu
4i
, 55%
4g
, 56%
4h
, 62%
a Unless otherwise noted, all reactions were carried out with:
(0.4 mmol), (0.2 mmol), KSeCN (0.6 mmol),
Ru(bpy)3(PF6)2 (2 mol%), and degassed CH3CN (2 mL) in a
culture tube under argon at rt irradiated with 12W blue LED
for 6 h. byield.
a Unless otherwise noted, all reactions were carried out with:
1v (0.4 mmol), (0.2 mmol), NH4SCN (0.6 mmol),
Ru(bpy)3(PF6)2 (2 mol%), and degassed CH3CN (2 mL) in a
culture tube under argon at rt irradiated with 12W blue LED
for 6 h. byield.
1
2
2
The practically synthetic potential of this new photo-
arylthiocyanation reaction could be highlighted by its
scalability and simplicity. The gram-scale reaction of 2c
under standard reaction conditions proceeded smoothly to
provide the corresponding product 4c in 69% yield (1.03
g) (Scheme 5A). To further illustrate the synthetic utility of
the present method, few experiments were carried out
(Scheme 5B). Upon treatment of 4d with TMSCF3 and
Cs2CO3, the SCN group was converted to SCF3 (6), a
prevalent lipophilic group presents in various
agrochemicals and pharmaceuticals (eq 1).27 In addition,
reaction of 4c with phenyl acetylene under palladium
catalysis, led cleanly to tri-substituted alkene 7 through a
regioselective cyanothiolation of alkyne by cleaving the
sulfur-cyano bond of SCN group (eq 2).28
Organoselenium compounds are ubiquitous in numbers
of molecules including biological, pharmaceutical, and
material interest.23 They show
a
wide range of
pharmaceutical activities like, antiviral, anti-inflammatory
and antitumor properties.24 Importantly, among
organoselenium compounds, the selenocyanate derivatives
displayed promising cancer chemopreventive agents25a-b
and
effective
antioxidants.25c
Furthermore,
organoselenium compounds can usually be used in a wide
varieties of organic transformations and have become a
versatile tool in organic synthesis.26 Keeping this in mind,
we conducted a series of experiments to validate this
intermolecular radical difunctionalization strategy to
access
arylsubstituted
alkylselenocyanate
using
selenocyanate salt instead of thiocyanate in our newly
developed transformation (scheme 4). Consequently, the
arylselenocyanation of alkene under the optimized
reaction conditions afforded the corresponding -aryl
alkylselenocyanates 5a-h in moderate to good yields. To
the best of our knowledge, this is the first reported
synthesis of -aryl alkylselenocyanates under visible light
photoredox catalysis. Several functional groups including
tert-butyl, methoxy, bromide, chloride, nitro, and phenyl
were tolerated in this reaction. Styrenes with para, meta
and ortho substituted groups (5a-d) were easily adaptable
under these mild photo catalytic conditions. Acrylates with
variable substituted ester handles were also well
accommodated to provide the desired arylselenocyanation
products (5f-h).
Scheme 5. A) Gram-scale photo-arylthiocyanation. B)
Diversification of arylthiocyanates.
OMe
A.
SCN
Ru(bpy)3(PF6)2
(2 mol%)
ArN2BF4
2c
NH4SCN
+
+
CH3CN, rt
blue LED
tBu
tBu
4c
1v
+
(1.03 g, 69%)
B.
Ph
SCF3
Cs2CO3,
TMSCF3
(1)
(2)
4d
4c
CH3CN, rt
63%
tBu
6
CN
OMe
Pd(PPh3)4 (10 mol%)
Ph
S
Ph
+
Toluene, 120 o
83%
C
Scheme 4. Scope of photo-arylselenocyanationa,b
tBu
7
To gain insight into the mechanistic pathways of the
raction, several control experiments were conducted.
Firstly, TEMPO, a radical-trapping reagent, was introduced
into the reaction mixture of 1v (Scheme 6A). Under these
conditions, no arylthiocyanation product 4c was found, but
4
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Fig 1. Stern-Volmer plots of Ru(bpy)3(PF6)2 quenching with
aryl-TEMPO 8 and benzyl-TEMPO 9 adducts were detected
by GC/MS analysis of the crude reaction mixture.
1
2
3
4
5
6
7
8
(A) 4-Methoxybenzene diazonium tetrafluoroborate, (B)
Ammonium thiocyanate and (C) 4-Methyl Styrene. (see the
supporting information for details).
Scheme 6. Mechanistic investigation.
A. Radical trapping experiment
TEMPO
9
Based on the above results and previous reports,12d-e
a
Ar
ArN2BF4 (2c)
stand. cond.
4c
plausible reaction mechanism for the present
photocatalyzed arylthiocyanation is proposed in Scheme
7a. Irradiation of Ru(II) with visible light yields a
photoexited *Ru(II), which reduces aryldiazonium salt 13
to aryl radical 14 via single electron transfer (SET) process
and itself oxidises to Ru(III). Addition of the aryl radical
to olefin generates a new radical intermediate 16, which is
further oxidized by Ru(III) to give a carbenium ion
intermediate30 17 and regenerating the photocatalyst.
Finally, 17 in presence of NH4SCN furnishes the arylated
alkylthiocyanate product 18. The key to the success of this
reaction is rely on efficient single electron oxidation of the
radical intermediate 16 to the corresponding cation 17,
which is relatively easy for aryl radical added styrenes, but
not for acrylates (bezylic radical vs acrylate radical).
However an alternative mechanism can be envisioned
(Scheme 7b), where this oxidation scenario can be
avoided.12i-k, 31 In this path the SCN group is transferred to
the adduct radical 16 from aryldiazo thiocyanate 19
present in the reaction mixture. Meanwhile the
aryldiazenyl radical 20, which is subsequently generated
during thiocyanate transfer step, then further propagates
the radical chain.
+
+
tBu
TEMPO Ar
8
NH4SCN
+
tBu
(0%)
TEMPO
(3 equiv)
1v
Ar
= p-OMeC6H4
Detected by GC/MS
B. Radical clock experiment
9
NCS
OMe
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
Ar2
stand. cond.
Ar2
SET [O]
Ar2N2BF4
Ar1
NH4SCN
Ar1
2c
Cl
Cl
I
10
11 (61%)
C. Nucleophilic trapping experiment
NO2
OMe
Ar2
Ar2
stand. cond.
MeOH
H
Ar1
Ar2N2BF4
2b
Ar1
1a
II
12 (64%)
These results indicate the photoredox process promotes
the generation of aryl radical and that the generated aryl
adduct (15, scheme 7) is one of the potential reactive
species in the reaction. Furthermore, reaction of -
cyclopropyl styrene 10 with diazonium salt 2c under our
standard conditions produced homoallylic thiocyanate 11
resulting from ring-opening of the cyclopropropylmethyl
radical (I), provides strong support for the participation of
aryl radical in this transformation (Scheme 6B). Finally, a
nucleophilic trapping experiment was conducted where
methanol was added into the reaction mixture in place of
ammonium thiocyanate (Scheme 6C). To our delight the
methylether product 12 was isolated in 64% yield,
providing direct evidence for the involvement of a
carbocation intermediate (II) in the reaction pathway.
Scheme 7. Plausible reaction mechanism
a)
R2
SCN
R1
SCN
Ar
Ar
R1
R2
NH4SCN
R3
R3
17
18
Ru (II)
blue LED
SET
R2
To probe the interaction of catalyst with substrates, a
standard Stern-Volmer experiment29 was conducted using
the employed substrates (Figure 1). It was observed that
the excited state of Ru(II)* showed a strongly enhanced
quenching effect with diazonium salt. However, trace or
very mild change of Ru(II)* luminescence in the presence
of variable concentration of styrene or thiocyanate salt
was observed. These results indicated that a oxidative
quenching of Ru(II)* by diazonium salt was involved in the
mechanism.
Ar
R1
R3
R2
16
*Ru (II)
Ru (III)
SET
R1
ArN2BF4
13
Ar
R3
15
14
b)
15
NH4SCN
- N2
Ar N2
R2
20
19
SCN
15
Ar
N
N
18
R1
- SCN
- N2
Ar
R3
19
16
CONCLUSIONS
In summary, we have developed a photoredox-catalyzed
intermolecular radical arylthiocyanation of alkenes with
arenediazonium salts and NH4SCN to construct both C-C
and C-S bonds simultaneously. The method is mild (visible
light, room temperature), operationally simple and
exhibits broad substrate scope with excellent functional
group
compatibility.
Furthermore,
-aryl
alkylselenocyanates were also synthesized using the
developed protocol with potassium selenocyanate.
EXPERIMENTAL SECTION
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The Journal of Organic Chemistry
Page 6 of 12
was filtered through a short pad of silica gel and eluted with
General Information.
1
2
3
4
5
6
7
8
Et2O (10 mL). The solution was concentrated and the residue
was purified by column chromatography on silica gel (EtOAc
in petroleum ether) to afford the corresponding product.
All commercially available chemicals and reagents were
used without any further purification unless otherwise stated.
All reactions were carried out in oven-dried glassware under
argon or nitrogen atmosphere with freshly distilled anhy-
drous solvents.32 Photoreactions were carried out in
borosilicate made reaction tube using blue light source
(PAR38 12W blue LED bulb). The progress of the reaction was
monitored by thin layer chromatography (TLC) using silica gel
Alumini-um Sheet (Merck, TLC Silica gel 60 F254). All
compounds were purified through column chromatography
using silica gel (230 – 400 mesh). Nuclear magnetic resonance
spectra were recorded on, Bruker Avance II 400, Bruker
Avance III 400, Bruker Avance III 500 and Jeol 400YH
instruments. Chemical shifts (δ) are quoted in ppm relative to
residual solvent signals, CDCl3 referenced at δ 7.26 ppm for 1H
and 77.16 ppm for 13C{1H}. TMS are used as internal standard
and Coupling constants (J) are quoted in hertz (Hz).
Multiplicity is reported with the following abbreviations: s =
singlet, d = doublet, t = triplet, q = quartet, dt = doublet of
triplets, td = triplet of doublets, tt = triplet of triplets. HRMS
were recorded using a QTOF micro MS system by ESI
technique. Elemental (CHN) analyses were carried out in
PerkinElmer CHNS/O analyzer (Model no-2400, series II). GC-
MS analysis was done by Thermo Scientific ISQ QD single
quadrupole GC-MS system using a TG-5MS column (30 m x
0.25 mm x 0.25 µm). Fluorescence quenching experiments
were performed using a PerkinElmer LS 55 Fluorescence
Spectrometer. Melting points (°C) are uncorrected.
Characterization Data of Products: 1–Methoxy–4-(2–
phenyl–2-thiocyanatoethyl) benzene (3a). Pale yellow
gummy solid; 74% yield (39 mg); Rf
value = 0.5
[EtOAc:petroleum ether = 1:9 (v/v)]; 1H NMR (400 MHz,
CDCl3) δ (ppm): 7.39 – 7.30 (m, 5H), 7.02 (d, J = 8.7 Hz, 2H),
6.80 (d, J = 8.7 Hz, 2H), 4.51 (t, J = 7.7 Hz, 1H), 3.77 (s, 3H),
3.37 (d, J = 7.7 Hz, 2H); 13C{1H} NMR (101 MHz, CDCl3) δ
(ppm): 158.9, 138.1, 130.3, 129.2, 129.1, 128.8, 127.8, 114.1,
111.8, 55.5, 55.3, 41.4; Anal. Calcd for C16H15NOS: C, 71.34; H,
5.61; N, 5.20%; Found: C, 71.17; H, 5.58; N, 5.36%.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1-Methoxy-4- (2-thiocyanato-2- (p-tolyl)ethyl) benzene
(3b). Pale yellow viscous liquid; 76% yield (43 mg); Rf value
= 0.6 [EtOAc:petroleum ether = 1:9 (v/v)]; 1H NMR (400 MHz,
CDCl3) δ (ppm): 7.21 (d, J = 8.1 Hz, 2H), 7.17 (d, J = 8.1 Hz, 2H),
7.02 (d, J = 8.5 Hz, 2H), 6.80 (d, J = 8.6 Hz, 2H), 4.50 (t, J = 7.7
Hz, 1H), 3.77 (s, 3H), 3.36 (d, J = 7.7 Hz, 2H), 2.35 (s, 3H);
13C{1H} NMR (101 MHz, CDCl3) δ (ppm): 158.8, 139.0, 135.0,
130.3, 129.8, 129.0, 127.7, 114.1, 112.0, 55.4, 55.3, 41.3, 21.3;
HRMS (ESI) m/z Calcd for C17H17NOSNa [M+Na]+: 306.0929;
Found: 306.0926.
4,4’-(1-Thiocyanatoethane-1,2-diyl)bis (methoxybenzene)
(3c). Pale yellow viscous liquid; 87% yield (52 mg); Rf value =
1
0.3 [EtOAc:petroleum ether = 1:9 (v/v)]; H NMR (400 MHz,
CDCl3) δ (ppm): 7.15 (d, J = 8.7 Hz, 2H), 7.02 (d, J = 8.6 Hz, 2H),
6.88 (d, J = 8.7 Hz, 2H), 6.83 (d, J = 8.6 Hz, 2H), 4.85 – 4.81(m,
1H), 3.81 (s, 3H), 3.80 (s, 3H), 3.14 – 3.04 (m, 2H); 13C{1H}
NMR (101 MHz, CDCl3) δ (ppm): 159.6, 158.9, 130.7, 128.3,
127.5, 114.2, 114.0, 63.1, 55.4, 55.3, 44.9; HRMS (ESI) m/z
Calcd for C17H21N2O2S [M+NH4]+: 317.1324; Found: 317.1326.
1,2-Dimethoxy-4- (2-(4-methoxyphenyl)-1- thiocyanato
ethyl) benzene (3d). Pale yellow viscous liquid; 70% yield (46
General Procedure for Preparation of Aryl Diazonium
Tetrafluoroborates.33 Method A: In a 50 ml round bottom
flask, the aniline (5.0 mmol) was dissolved in a mixture of
distilled water (1 ml) and an aqueous solution of fluoroboric
acid (50% in water, 1.9 ml) in rt. The mixture was cooled to
0°C with an ice bath and a solution of sodium nitrite (0.68 g in
1 ml water) was added dropwise. After addition the reaction
mixture was stirred at 0°C for 1h. A thick precipitate was
formed, collected by filtration and dissolved in minimum
amount of acetone. Then diazonium salt was reprecipitated by
the addition of diethyl ether. The aryl diazonium salt was
filtered, washed three times with diethyl ether and dried in
vacuo and used directly without further purification.
1
mg); Rf value = 0.4 [EtOAc:petroleum ether = 1:4 (v/v)]; H
NMR (500 MHz, CDCl3) δ (ppm): 7.01 (d, J = 8.6 Hz, 2H), 6.82
(dd, J = 8.5, 2.2 Hz, 3H), 6.77 (dd, J = 8.2, 2.1 Hz, 1H), 6.67 (d, J
= 2.0 Hz, 1H), 4.82 (dd, J = 7.6, 6.0 Hz, 1H), 3.88 (s, 3H), 3.84 (s,
3H), 3.79 (s, 3H), 3.10 (dd, J = 9.7, 6.8 Hz, 2H); 13C{1H} NMR
(101 MHz, CDCl3) δ (ppm): 158.9, 149.1, 149.0, 131.1, 130.8,
128.3, 118.6, 114.0, 111.1, 109.3, 63.4, 56.1, 55.4, 44.9; Anal.
Calcd for C18H19NO3S: C, 65.63; H, 5.81; N, 4.25%; Found: C,
66.02; H, 5.57; N, 4.12%.
1-Fluoro-4- (2-(4-methoxyphenyl)-1- thiocyanatoethyl)
benzene (3e). Pale yellow gummy solid; 82% yield (47 mg); Rf
value = 0.4 [EtOAc:petroleum ether = 1:9 (v/v)]; 1H NMR (400
MHz, CDCl3) δ (ppm): 7.31 – 7.28 (m, 2H), 7.07 – 6.99 (m, 4H),
6.80 (d, J = 8.6 Hz, 2H), 4.51 (t, J = 7.7 Hz, 1H), 3.77 (s, 3H),
3.33 (dd, J = 7.7, 5.5 Hz, 2H); 13C{1H} NMR (101 MHz, CDCl3) δ
(ppm): 162.9 (d, J = 248.8 Hz), 158.9, 134.0 (d, J = 3.3 Hz),
130.3, 129.6(d, J = 8.6 Hz), 128.5, 116.2 (d, J = 21.8 Hz), 114.2,
111.6, 55.3, 54.7, 41.4; 19F NMR (376 MHz, CDCl3) δ -111.9 (s,
1F); Anal. Calcd for C16H14FNOS: C, 66.88; H, 4.91; N, 4.87%;
Found: C, 66.79; H, 4.62; N, 4.92%.
1-Bromo-4- (2-(4-methoxyphenyl)-1- thiocyanatoethyl)
benzene (3f). Pale yellow viscous liquid; 79% yield (55 mg);
Rf value = 0.4 [EtOAc:petroleum ether = 1:9 (v/v)]; 1H NMR
(400 MHz, CDCl3) δ (ppm): 7.49 (d, J = 8.5 Hz, 2H), 7.19 (d, J =
8.5 Hz, 2H), 7.00 (d, J = 8.6 Hz, 2H), 6.80 (d, J = 8.7 Hz, 2H),
4.47 (t, J = 7.7 Hz, 1H), 3.77 (s, 3H), 3.32 (dd, J = 7.7, 4.2 Hz,
2H); 13C{1H} NMR (101 MHz, CDCl3) δ (ppm): 159.0, 137.2,
132.3, 130.3, 129.4, 128.3, 123.1, 114.2, 111.4, 55.3, 54.7,
41.1; Anal. Calcd for C16H14BrNOS: C, 55.18; H, 4.05; N, 4.02%;
Found: C, 55.39; H, 3.63; N, 3.92%.
Method B: In a 50 ml round bottom flask, the aniline (5
mmol) was dissolved in a mixture of absolute ethanol (2 mL)
and an aqueous solution of fluoroboric acid (50%, 1.9 ml). The
mixture was cooled to 0°C with an ice bath and tert-butyl
nitrite (1.4 ml) was added dropwise. After addition the
reaction mixture was stirred at 0°C for 30 min and another 1h
at rt. Then diethyl ether (20 ml) was added to precipitate the
diazonium salt. The thick precipitate was filtered off and
washed three times with diethyl ether. Then diazonium salt
was dried in vacuo and used directly without further
purification.
General
Procedure
of
Photoredox-Catalysed
Arylthiocyanation of Alkene: A culture tube equipped with
magnetic stir bar was charged with Ru(bpy)3(PF6)2 (3.5 mg,
0.004 mmol, 2 mol%), aryldiazonium tetrafluoroborate (0.2
mmol) and degassed acetonitrile (2 ml). The tube was sealed
with a Teflon screw cap, before styrene (0.4 mmol) and
ammonium thiocyanate (0.6 mmol) were added to it. Then the
orange reaction mixture was degassed with argon and
irradiated at rt with a 12W blue LED bulb at a distance of app.
8 cm for 6h. A high-speed fan was used to maintain the
temperature. After the reaction was complete, the mixture
6
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The Journal of Organic Chemistry
Hz, 1H), 7.53 – 7.46 (m, 3H), 7.05 (d, J = 8.6 Hz, 2H), 6.79 (d, J
1-Chloro-4- (2-(4-methoxyphenyl)-1- thiocyanatoethyl)
= 8.7 Hz, 2H), 4.70 (t, J = 7.7 Hz, 1H), 3.76 (s, 3H), 3.47 (dd, J =
7.7, 2.0 Hz, 2H); 13C{1H} NMR (101 MHz, CDCl3) δ (ppm):
158.9, 135.3, 133.5, 133.2, 130.3, 129.3, 128.8, 128.3, 127.9,
127.4, 126.9, 126.8, 124.8, 114.9, 111.8, 55.8, 55.3, 41.2;
HRMS (ESI) m/z Calcd for C20H21N2OS [M+NH4]+: 337.1375;
Found: 337.1374.
benzene (3g). Pale yellow solid; mp: 75 – 77 °C; 81% yield (49
1
2
mg); Rf value = 0.4 [EtOAc:petroleum ether = 1:9 (v/v)]; H
NMR (400 MHz, CDCl3) δ (ppm): 7.25 (d, J = 8.5 Hz, 2H), 7.17
(d, J = 8.3 Hz, 2H), 6.92 (d, J = 8.7 Hz, 2H), 6.72 (d, J = 8.6 Hz,
2H), 4.40 (t, J = 7.7 Hz, 1H), 3.69 (s, 3H), 3.24 (dd, J = 7.7, 4.6
Hz, 2H); 13C{1H} NMR (101 MHz, CDCl3) δ (ppm): 159.0, 136.7,
134.9, 130.3, 129.4, 129.2, 128.4, 114.2, 111.4, 55.3, 54.6,
41.2; Anal. Calcd for C16H14ClNOS: C, 63.25; H, 4.64; N, 4.61%;
Found: C, 62.96; H, 4.42; N, 4.51%.
3
4
5
6
7
8
3-(2-(4-Methoxyphenyl)-1- thiocyanatoethyl) pyridine
(3n). Pale yellow viscous liquid; 44% yield (24 mg); Rf value =
0.3 [EtOAc:petroleum ether = 3:7 (v/v)]; H NMR (400 MHz,
1
9
CDCl3) δ (ppm): 8.59 (d, J = 4.7 Hz, 1H), 8.53 (d, J = 1.6 Hz, 1H),
7.70 (d, J = 8.0 Hz, 1H), 7.33 (dd, J = 7.8, 4.9 Hz, 1H), 7.01 (d, J =
8.4 Hz, 2H), 6.80 (d, J = 8.5 Hz, 2H), 4.51 (t, J = 7.7 Hz, 1H), 3.77
(s, 3H), 3.35 (dd, J = 9.7, 8.1 Hz, 2H); 13C{1H} NMR (101 MHz,
CDCl3) δ (ppm): 159.1, 150.2, 149.1, 135.2, 134.3, 130.3,
127.9, 124.0, 114.3, 111.0, 55.4, 52.5, 40.9; HRMS (ESI) m/z
Calcd for C15H15N2OS [M+H]+: 271.0900; Found: 271.0902.
1-Fluoro-4- (2-(4-methoxyphenyl)- 1-thiocyanatopropyl)
benzene (3o). Pale yellow viscous liquid; 60% yield (36 mg);
1-Chloro-3- (2-(4-methoxyphenyl)-1- thiocyanatoethyl)
benzene (3h). Pale yellow viscous liquid; 79% yield (48 mg);
Rf value = 0.4 [EtOAc:petroleum ether = 1:9 (v/v)]; H NMR
(400 MHz, CDCl3) δ (ppm): 7.33 – 7.30 (m, 3H), 7.22 – 7.19 (m,
1H), 7.02 (d, J = 8.6 Hz, 2H), 6.81 (d, J = 8.7 Hz, 2H), 4.46 (t, J =
7.7 Hz, 1H), 3.78 (s, 3H), 3.32 (d, J = 7.7 Hz, 2H); 13C{1H} NMR
(101 MHz, CDCl3) δ (ppm): 159.0, 140.2, 135.0, 130.4, 130.3,
129.3, 128.3, 127.9, 126.0, 114.3, 111.3, 55.4, 54.7, 41.1;
HRMS (ESI) m/z Calcd for C16H18ClN2OS [M+NH4]+: 321.0828;
Found: 321.0827.
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
1
1
Rf value = 0.4 [EtOAc:petroleum ether = 1:9 (v/v)]; H NMR
(400 MHz, CDCl3) δ (ppm): (for the mixture) 7.37 (dd, J = 8.5,
5.3 Hz, 2H), 7.18 (d, J = 8.6 Hz, 2H), 7.13 – 7.06 (m, 4H), 6.94 –
6.88 (m, 6H), 6.71 (d, J = 8.6 Hz, 2H), 4.47 – 4.44 (m, 2H), 3.82
(s, 3H), 3.73 (s, 3H), 3.38 (dd, J = 9.0, 7.1 Hz, 1H), 3.26 (dd, J =
10.4, 6.9 Hz, 1H), 1.51 (d, J = 6.9 Hz, 3H), 1.16 (d, J = 6.9 Hz,
3H); 13C{1H} NMR (101 MHz, CDCl3) δ (ppm): (for major
isomer) 162.4 (d, J = 249.5 Hz), 159.3, 134.2 (d, J = 3.5 Hz),
133.4, 130.0, 128.8, 115.7 (d, J = 21.6 Hz), 113.9, 111.9, 60.2,
55.3, 44.4, 20.7; (for minor isomer) 161.9 (d, J = 249.5 Hz),
158.6, 134.0 (d, J = 3.5 Hz), 133.9, 129.9, 128.5, 115.7 (d, J =
21.6 Hz), 114.4, 112.0, 60.7, 55.4, 44.9, 20.7; 19F NMR (376
MHz, CDCl3) δ -114.2 (s, 1F); HRMS (ESI) m/z Calcd for
C17H16FNOSNa [M+Na]+: 324.0834; Found: 324.0835.
1-Chloro-2- (2-(4-methoxyphenyl)-1- thiocyanatoethyl)
benzene (3i). Pale yellow viscous liquid; 77% yield (47 mg);
1
Rf value = 0.4 [EtOAc:petroleum ether = 1:9 (v/v)]; H NMR
(400 MHz, CDCl3) δ (ppm): 7.54 (dd, J = 7.7, 1.6 Hz, 1H), 7.40
(dd, J = 7.8, 1.4 Hz, 1H), 7.35 (td, J = 7.6, 1.4 Hz, 1H), 7.29 (dd, J
= 7.7, 1.7 Hz, 1H), 7.12 (d, J = 8.7 Hz, 2H), 6.84 (d, J = 8.7 Hz,
2H), 4.98 (t, J = 7.7 Hz, 1H), 3.79 (s, 3H), 3.39 (d, J = 7.7 Hz,
2H); 13C{1H} NMR (101 MHz, CDCl3) δ (ppm): 159.0, 135.9,
133.8, 130.3, 130.2, 130.0, 128.5, 128.3, 127.7, 114.2, 111.2,
55.4, 50.8, 40.0; Anal. Calcd for C16H14ClNOS: C, 63.25; H, 4.64;
N, 4.61%; Found: C, 63.05; H, 4.29; N, 4.24%.
1-(2-(4-Methoxyphenyl)-1-
thiocyanatoethyl)-2-nitro
benzene (3j). Pale yellow viscous liquid; 73% yield (46 mg);
1
(1-(4-Methoxyphenyl)-2- thiocyanatoethane-1,2-diyl) di
benzene (3p). Pale yellow viscous liquid; 58% yield (40 mg);
Rf value = 0.3 [EtOAc:petroleum ether = 1:9 (v/v)]; H NMR
(500 MHz, CDCl3) δ (ppm): 7.99 (dd, J = 8.2, 1.2 Hz, 1H), 7.79
(dd, J = 7.9, 1.2 Hz, 1H), 7.72 (td, J = 7.8, 1.2 Hz, 1H), 7.54 –
7.50 (m, 1H), 7.13 (d, J = 8.6 Hz, 2H), 6.84 (d, J = 8.6 Hz, 2H),
5.24 (dd, J = 8.8, 6.4 Hz, 1H), 3.79 (s, 3H), 3.41 (dd, J = 15.3, 7.6
Hz, 2H); 13C{1H} NMR (101 MHz, CDCl3) δ (ppm): 159.2, 148.1,
134.1, 130.3, 129.7, 128.9, 128.0, 125.6, 114.4, 111.0, 55.4,
48.6, 40.3; HRMS (ESI) m/z Calcd for C16H14N2O3SNa [M+Na]+:
337.0623; Found: 337.0621.
1
Rf value = 0.3 [EtOAc:petroleum ether = 1:9 (v/v)]; H NMR
(400 MHz, CDCl3) δ (ppm): (for the mixture) 7.45 (d, J = 7.2
Hz, 2H), 7.39 – 7.34 (m, 8H), 7.31 – 7.27 (m, 6H), 7.25 – 7.21
(m, 2H), 7.11 (d, J = 4.3 Hz, 4H), 7.03 (d, J = 8.7 Hz, 2H), 6.90
(d, J = 8.7 Hz, 2H), 6.64 (d, J = 8.8 Hz, 2H), 5.11 (dd, J = 12.0, 9.7
Hz, 2H), 4.53 (dd, J = 12.0, 3.4 Hz, 2H), 3.80 (s, 3H), 3.66 (s,
3H); 13C{1H} NMR (101 MHz, CDCl3) δ (ppm): (for major
isomer) 159.2, 140.9, 138.1, 132.7, 129.3, 129.0, 128.9, 128.7,
128.3, 127.8, 126.9, 114.0, 111.6, 58.2, 55.9, 55.2; (for minor
isomer) 158.3, 140.9, 138.1, 132.6, 129.1, 128.9, 128.8, 128.7,
128.1, 127.8, 126.9, 114.5, 111.7, 58.6, 55.9, 55.4; HRMS (ESI)
m/z Calcd for C22H19NOSNa [M+Na]+: 368.1085; Found:
368.1087.
4-(2-(4-Methoxyphenyl)-1-thiocyanatoethyl)
phenyl
acetate (3k). Pale yellow solid; mp: 97 – 99 °C; 84% yield (55
mg); Rf value = 0.3 [EtOAc:petroleum ether = 1:9 (v/v)]; 1H
NMR (400 MHz, CDCl3) δ (ppm): 7.33 (d, J = 8.6 Hz, 2H), 7.10
(d, J = 8.6 Hz, 2H), 7.02 (d, J = 8.6 Hz, 2H), 6.80 (d, J = 8.7 Hz,
2H), 4.49 (t, J = 7.7 Hz, 1H), 3.77 (s, 3H), 3.34 (d, J = 7.7 Hz,
2H), 2.30 (s, 3H); 13C{1H} NMR (101 MHz, CDCl3) δ (ppm):
169.2, 158.9, 151.0, 135.6, 130.3, 128.9, 128.6, 122.3, 114.2,
111.6, 55.3, 54.8, 41.3, 21.2; HRMS (ESI) m/z Calcd for
C18H17NO3SNa [M+Na]+: 350.0827; Found: 350.0825.
1-(Chloromethyl)-4- (2-(4-methoxyphenyl)-1- thiocyana
toethyl) benzene (3l). Pale yellow viscous liquid; 49% yield
(31 mg); Rf value = 0.3 [EtOAc:petroleum ether = 1:9 (v/v)];
1H NMR (400 MHz, CDCl3) δ (ppm): 7.39 (d, J = 8.2 Hz, 2H),
7.32 (d, J = 8.2 Hz, 2H), 7.02 (d, J = 8.6 Hz, 2H), 6.80 (d, J = 8.6
Hz, 2H), 4.58 (s, 2H), 4.51 (t, J = 7.7 Hz, 1H), 3.77 (s, 3H), 3.35
(d, J = 7.7 Hz, 2H); 13C{1H} NMR (101 MHz, CDCl3) δ (ppm):
158.9, 138.4, 138.3, 130.3, 129.3, 128.6, 128.2, 114.2, 111.6,
55.3, 55.0, 45.7, 41.2; HRMS (ESI) m/z Calcd for
C17H16ClNOSNa [M+Na]+: 340.0539; Found: 340.0541.
(E)-1-Methoxy-4-(4-phenyl- 2-thiocyanatobut-3-en-1-yl)
benzene (3q). Pale yellow viscous liquid; 42% yield (25 mg);
1
Rf value = 0.4 [EtOAc:petroleum ether = 1:19 (v/v)]; H NMR
(400 MHz, CDCl3) δ (ppm): 7.37 – 7.28 (m, 5H), 7.16 (d, J = 8.6
Hz, 2H), 6.88 (d, J = 8.7 Hz, 2H), 6.60 (dd, J = 15.7, 1.2 Hz, 1H),
6.12 (dd, J = 15.8, 6.3 Hz, 1H), 4.53 (qd, J = 6.6, 1.3 Hz, 1H),
3.81 (s, 3H), 3.01 (d, J = 6.7 Hz, 2H); 13C{1H} NMR (101 MHz,
CDCl3) δ (ppm): 159.0, 135.8, 132.3, 130.8, 128.8, 128.4,
128.1, 126.8, 126.0, 114.2, 61.5, 55.4, 42.8; HRMS (ESI) m/z
Calcd for C18H17NOSNa [M+Na]+: 318.0929; Found: 318.0927.
3-(4-Methoxyphenyl)-2- thiocyanato propanenitrile (3r).
Pale yellow viscous liquid; 64% yield (28 mg); Rf value = 0.5
[EtOAc:petroleum ether = 1:9 (v/v)]; 1H NMR (400 MHz,
CDCl3) δ (ppm): 7.21 (d, J = 8.7 Hz, 2H), 6.92 (d, J = 8.7 Hz, 2H),
4.04 – 4.01 (m, 1H), 3.82 (s, 3H), 3.37 – 3.23 (m, 2H); 13C{1H}
NMR (101 MHz, CDCl3) δ (ppm): 160.0, 130.6, 125.3, 115.8,
114.8, 107.9, 55.5, 38.6, 37.1; HRMS (ESI) m/z Calcd for
C11H10N2OSNa [M+Na]+: 241.0412; Found: 241.0462.
2-(2-(4-Methoxyphenyl)-1- thiocyanatoethyl) naphthalene
(3m). Pale yellow solid; mp: 104 – 106 °C; 80% yield (51 mg);
Rf value = 0.4 [EtOAc:petroleum ether = 1:9 (v/v)]; 1H NMR
(400 MHz, CDCl3) δ (ppm): 7.89 – 7.81 (m, 3H), 7.75 (d, J = 1.3
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128.9, 127.5, 127.4, 127.1, 126.1, 111.9, 55.0, 41.6, 34.8, 31.4;
tert-Butyl 3-(4-methoxyphenyl)-2-thiocyanatopropanoate
HRMS (ESI) m/z Calcd for C25H25NSNa [M+Na]+: 394.1606;
Found: 394.1603.
1
2
3
4
5
6
7
8
(3s). Pale yellow viscous liquid; 44% yield (26 mg); Rf value =
1
0.3 [EtOAc:petroleum ether = 1:19 (v/v)]; H NMR (400 MHz,
1-(Tert-butyl)-4- (1-thiocyanato-2- (4-(trifluoromethyl)
phenyl) ethyl) benzene (4e). Pale yellow solid; mp: 78 – 80
°C; 62% yield (45 mg); Rf value = 0.6 [EtOAc:petroleum ether
CDCl3) δ (ppm): 7.15 (d, J = 8.7 Hz, 2H), 6.85 (d, J = 8.7 Hz, 2H),
3.84 (d, J = 7.4 Hz, 1H), 3.80 (s, 3H), 3.21 (ddd, J = 60.6, 14.3,
7.4 Hz, 2H), 1.45 (s, 9H); 13C{1H} NMR (101 MHz, CDCl3) δ
(ppm): 167.4, 159.1, 130.4, 127.5, 114.1, 110.2, 84.0, 55.3,
51.6, 37.1, 27.8; HRMS (ESI) m/z Calcd for C15H23N2O3S
[M+NH4]+: 311.1429; Found: 311.1427.
1
= 1:9 (v/v)]; H NMR (400 MHz, CDCl3) δ (ppm): 7.53 (d, J =
8.1 Hz, 2H), 7.38 (d, J = 8.3 Hz, 2H), 7.24 (dd, J = 8.2, 3.9 Hz,
4H), 4.52 (t, J = 7.6 Hz, 1H), 3.51 (dd, J = 7.6, 2.3 Hz, 2H), 1.31
(s, 9H); 13C{1H} NMR (101 MHz, CDCl3) δ (ppm): 152.6, 141.0,
134.3, 129.9 (q, J = 34.0 Hz), 129.7, 127.3, 127.2 (q, J = 276.0
Hz), 126.3, 125.7(q, J = 4.0 Hz), 111.6, 54.4, 41.8, 34.9, 31.3;
19F NMR (376 MHz, CDCl3) δ -62.4(s, 3F); HRMS (ESI) m/z
Calcd for C20H20F3NSNa [M+Na]+: 386.1166; Found: 386.1164.
Methyl
3-(4-methoxyphenyl)-2-methyl-2-thiocyanato
9
propanoate (3t). Pale yellow viscous liquid; 60% yield (32
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13
14
15
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21
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60
mg); Rf value = 0.4 [EtOAc:petroleum ether = 1:9 (v/v)]; H
NMR (500 MHz, CDCl3) δ (ppm): 7.10 (d, J = 8.6 Hz, 2H), 6.84
(d, J = 8.5 Hz, 2H), 3.79 (s, 3H), 3.79 (s, 3H), 3.25 (q, J = 14.2
Hz, 2H), 1.76 (s, 3H); 13C{1H} NMR (101 MHz, CDCl3) δ (ppm):
170.8, 159.2, 131.1, 126.5, 113.9, 111.0, 61.0, 55.2, 53.4, 44.1,
24.9; HRMS (ESI) m/z Calcd for C13H15NO3SNa [M+Na]+:
288.0670; Found: 288.0668.
1-(2-(4-(tert-Butyl)
phenyl)-
2-thiocyanatoethyl)-2-
methoxybenzene (4f). Pale yellow viscous liquid; 38% yield
(25 mg); Rf value = 0.4 [EtOAc:petroleum ether = 1:19 (v/v)];
1H NMR (400 MHz, CDCl3) δ (ppm): 7.39 (d, J = 8.4 Hz, 2H),
7.31 (d, J = 8.4 Hz, 2H), 7.28 – 7.23 (m, 1H), 7.10 (dd, J = 7.6,
1.6 Hz, 1H), 6.89 – 6.86 (m, 2H), 4.72 (t, J = 7.6 Hz, 1H), 3.83 (s,
3H), 3.43 – 3.31 (m, 2H), 1.32 (s, 9H); 13C{1H} NMR (101 MHz,
CDCl3) δ (ppm): 157.7, 151.8, 136.1, 131.3, 128.8, 127.3,
125.9, 125.4, 120.6, 112.3, 110.5, 55.4, 53.5, 37.3, 34.8, 31.4;
HRMS (ESI) m/z Calcd for C20H23NOSNa [M+Na]+: 348.1398;
Found: 348.1394.
(E)-1-(4-Methoxystyryl) pyrrolidin-2-one (3u).34 White
solid; mp: 104 – 106 °C; 53% yield (23 mg); Rf value = 0.3
[EtOAc:petroleum ether = 3:7 (v/v)]; 1H NMR (500 MHz,
CDCl3) δ (ppm): 7.50 (d, J = 14.9 Hz, 1H), 7.28 (d, J = 8.7 Hz,
2H), 6.84 (d, J = 8.7 Hz, 2H), 5.85 (d, J = 14.8 Hz, 1H), 3.80 (s,
3H), 3.64 (t, J = 7.2 Hz, 2H), 2.53 (t, J = 8.2 Hz, 2H), 2.18 – 2.12
(m,2H); 13C{1H} NMR (101 MHz, CDCl3) δ (ppm): 173.2, 158.5,
129.0, 126.8, 122.1, 114.2, 111.5, 55.3, 45.3, 31.3, 17.5; HRMS
(ESI) m/z Calcd for C13H15NO2Na [M+Na]+: 240.1000; Found:
240.0989.
1-(3-(2-(4-(Tert-butyl)phenyl)-2-
thiocyanatoethyl)
phenyl) ethan-1-one (4g). Pale yellow solid; mp: 57 – 59 °C;
56% yield (38 mg); Rf value = 0.3 [EtOAc:petroleum ether =
1
4-(2-(4-(Tert-butyl)
phenyl)-2-
thiocyanatoethyl)
1:9 (v/v)]; H NMR (400 MHz, CDCl3) δ (ppm): 7.82 (d, J = 7.3
Hz, 1H), 7.64 (s, 1H), 7.39 – 7.34 (m, 4H), 7.25 (d, J = 8.6 Hz,
2H), 4.54 (t, J = 7.7 Hz, 1H), 3.50 (dd, J = 7.6, 2.1 Hz, 2H), 2.52
(s, 3H), 1.31 (s, 9H); 13C{1H} NMR (101 MHz, CDCl3) δ (ppm):
197.8, 152.4, 137.4, 137.3, 134.4, 133.9, 129.0, 128.9, 127.3,
126.1, 111.5, 54.5, 41.9, 34.7, 31.2, 26.6; HRMS (ESI) m/z
Calcd for C21H23NOSNa [M+Na]+: 360.1398; Found: 360.1396.
5-(2-(4-(Tert-butyl) phenyl)-2- thiocyanatoethyl) benzo
[d][1,3]dioxole (4h). Pale yellow viscous liquid; 62% yield (42
benzonitrile (4a). Pale yellow viscous liquid; 70% yield (45
mg); Rf value = 0.3 [EtOAc:petroleum ether = 1:9 (v/v)]; 1H
NMR (400 MHz, CDCl3) δ (ppm): 7.55 (d, J = 8.3 Hz, 2H), 7.38
(d, J = 8.4 Hz, 2H), 7.22 (d, J = 8.1 Hz, 4H), 4.52 (t, J = 7.7 Hz,
1H), 3.57 – 3.46 (m, 2H), 1.31 (s, 9H); 13C{1H} NMR (101 MHz,
CDCl3) δ (ppm): 152.7, 142.3, 133.9, 132.5, 130.1, 127.3,
126.8, 126.3, 118.7, 111.4, 54.0, 42.1, 34.8, 31.3; HRMS (ESI)
m/z Calcd for C20H20N2SNa [M+Na]+: 343.1245; Found:
343.1246.
1
mg); Rf value = 0.5 [EtOAc:petroleum ether = 1:9 (v/v)]; H
1-(Tert-butyl)-4-(2-(4-nitrophenyl)-1- thiocyanato ethyl)
benzene (4b). Pale yellow viscous liquid; 57% yield (39 mg);
NMR (400 MHz, CDCl3) δ (ppm): 7.38 (d, J = 8.4 Hz, 2H), 7.25
(d, J = 6.7 Hz, 2H), 6.70 (d, J = 8.5 Hz, 1H), 6.59 (d, J = 6.7 Hz,
2H), 5.92 (s, 2H), 4.47 (t, J = 7.6 Hz, 1H), 3.33 (d, J = 7.4 Hz,
2H), 1.31 (s, 9H); 13C{1H} NMR (101 MHz, CDCl3) δ (ppm):
152.3, 147.9, 146.9, 135.0, 130.7, 127.4, 126.1, 122.6, 111.9,
109.5, 108.5, 101.2, 55.4, 41.8, 34.8, 31.4; HRMS (ESI) m/z
Calcd for C20H21NO2SNa [M+Na]+: 362.1191; Found: 362.1194.
1
Rf value = 0.4 [EtOAc:petroleum ether = 1:9 (v/v)]; H NMR
(400 MHz, CDCl3) δ (ppm): 8.12 (d, J = 8.7 Hz, 2H), 7.38 (d, J =
8.4 Hz, 2H), 7.27 (d, J = 8.9 Hz, 2H), 7.23 (d, J = 8.4 Hz, 2H),
4.55 (t, J = 7.7 Hz, 1H), 3.63 – 3.51 (m, 2H), 1.30 (s, 9H);
13C{1H} NMR (101 MHz, CDCl3) δ (ppm): 152.8, 147.3, 144.4,
133.7, 130.2, 127.3, 126.4, 124.0, 111.4, 54.0, 41.9, 34.9, 31.3;
HRMS (ESI) m/z Calcd for C19H20N2O2SNa [M+Na]+: 363.1143;
Found: 363.1148.
3-(2-(4-(Tert-butyl)
phenyl)-2-thiocyanatoethyl)
quinoline (4i). Pale yellow gummy solid; 55% yield (38 mg);
Rf value = 0.4 [EtOAc:petroleum ether = 3:7 (v/v)]; 1H NMR
(400 MHz, CDCl3) δ (ppm): 8.64 (d, J = 2.2 Hz, 1H), 8.06 (d, J =
8.4 Hz, 1H), 7.90 (d, J = 1.9 Hz, 1H), 7.75 – 7.67 (m, 2H), 7.54
(ddd, J = 8.0, 7.0, 1.0 Hz, 1H), 7.38 (d, J = 8.4 Hz, 2H), 7.27 (d, J
= 8.4 Hz, 2H), 4.62 (t, J = 7.6 Hz, 1H), 3.65 (dd, J = 7.6, 3.8 Hz,
2H), 1.30 (s, 9H); 13C{1H} NMR (101 MHz, CDCl3) δ (ppm):
152.7, 151.4, 147.4, 136.2, 133.9, 129.8, 129.7, 129.3, 127.9,
127.7, 127.4, 127.2, 126.4, 111.6, 54.4, 39.5, 34.8, 31.3; HRMS
(ESI) m/z Calcd for C22H23N2S [M+H]+: 347.1577; Found:
347.1575.
1-(Tert-butyl)-4-(2- (4-methoxyphenyl)-1- selenocyana-
toethyl) benzene (5a). Pale yellow viscous liquid; 67% yield
(50 mg); Rf value = 0.5 [EtOAc:petroleum ether = 1:9 (v/v)];
1H NMR (400 MHz, CDCl3) δ (ppm): 7.36 (d, J = 8.5 Hz, 2H),
7.28 (d, J = 8.5 Hz, 2H), 7.05 (d, J = 8.6 Hz, 2H), 6.80 (d, J = 8.6
Hz, 2H), 4.80 (t, J = 7.8 Hz, 1H), 3.77 (s, 3H), 3.48 (t, J = 7.3 Hz,
2H), 1.31 (s, 9H); 13C{1H} NMR (101 MHz, CDCl3) δ (ppm):
158.8, 152.0, 136.0, 130.1, 127.4, 126.0, 116.0, 114.0, 102.6,
1-(Tert-butyl)-4- (2-(4-methoxyphenyl)-1- thiocyanato
ethyl) benzene (4c). Pale yellow viscous liquid; 75% yield (49
1
mg); Rf value = 0.6 [EtOAc:petroleum ether = 1:9 (v/v)]; H
NMR (400 MHz, CDCl3) δ (ppm): 7.37 (d, J = 8.4 Hz, 2H), 7.25
(d, J = 5.8 Hz, 2H), 7.04 (d, J = 8.5 Hz, 2H), 6.80 (d, J = 8.6 Hz,
2H), 4.48 (t, J = 7.6 Hz, 1H), 3.77 (s, 3H), 3.36 (d, J = 8.0 Hz,
2H), 1.31 (s, 9H); 13C{1H} NMR (101 MHz, CDCl3) δ (ppm):
158.9, 152.2, 135.2, 130.4, 129.1, 127.4, 126.1, 114.1, 112.0,
55.5, 55.4, 41.3, 34.8, 31.4; Anal. Calcd for C20H23NOS: C, 73.81;
H, 7.12; N, 4.30%; Found: C, 74.19; H, 7.06; N, 4.37%.
4-(2-(4-(Tert-butyl) phenyl)-2- thiocyanatoethyl)-1,1'-
biphenyl (4d). Pale yellow gummy solid; 72% yield (54 mg);
Rf value = 0.5 [EtOAc:petroleum ether = 1:9 (v/v)]; 1H NMR
(400 MHz, CDCl3) δ (ppm): 7.57 (d, J = 7.1 Hz, 2H), 7.51 (d, J =
8.2 Hz, 2H), 7.45 – 7.39 (m, 4H), 7.35 (d, J = 7.4 Hz, 1H), 7.30
(d, J = 8.4 Hz, 2H), 7.21 (d, J = 8.2 Hz, 2H), 4.57 (t, J = 7.7 Hz,
1H), 3.48 (d, J = 7.7 Hz, 2H), 1.32 (s, 9H); 13C{1H} NMR (101
MHz, CDCl3) δ (ppm): 152.2, 140.6, 140.2, 136.1, 135.0, 129.7,
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The Journal of Organic Chemistry
55.5, 52.9, 41.8, 34.7, 31.2; HRMS (ESI) m/z Calcd for
Phenyl-3-(4-methoxyphenyl)-2-
propanoate (5h). Pale yellow viscous liquid: 40% yield (29
mg); Rf value = 0.5 [EtOAc:petroleum ether = 1:9 (v/v)]; H
NMR (400 MHz, CDCl3) δ (ppm): 7.39 – 7.35 (m, 2H), 7.27 –
7.21 (m, 3H), 7.04 (dd, J = 8.6, 1.1 Hz, 2H), 6.89 (d, J = 8.7 Hz,
2H), 4.32 (dd, J = 8.3, 6.7 Hz, 1H), 3.80 (s, 3H), 3.44 (ddd, J =
21.1, 14.4, 7.5 Hz, 2H); 13C{1H} NMR (101 MHz, CDCl3) δ
(ppm): 168.2, 159.3, 150.2, 130.9, 129.6, 127.9, 126.5, 121.1,
114.4, 99.8, 55.3, 46.1, 37.5; HRMS (ESI) m/z Calcd for
C17H15NO3SeNa [M+Na]+: 384.0116; Found: 384.0115.
selenocyanato
C20H23NOSeNa [M+Na]+: 396.0844; Found: 396.0842.
1
2
3
4
5
6
7
8
1
1-Bromo-3-(2-(4-methoxyphenyl)-1- selenocyanato ethyl)
benzene (5b). Pale yellow viscous liquid; 57% yield (45 mg);
1
Rf value = 0.4 [EtOAc:petroleum ether = 1:9 (v/v)]; H NMR
(500 MHz, CDCl3) δ (ppm): 7.49 (t, J = 1.7 Hz, 1H), 7.46 – 7.43
(m, 1H), 7.29 – 7.26 (m, 1H), 7.23 (t, J = 7.8 Hz, 1H), 7.03 (d, J =
8.6 Hz, 2H), 6.81 (d, J = 8.7 Hz, 2H), 4.72 (t, J = 7.9 Hz, 1H), 3.78
(s, 3H), 3.43 (dd, J = 7.9, 5.4 Hz, 2H); 13C{1H} NMR (101 MHz,
CDCl3) δ (ppm): 158.9, 141.0, 132.0, 130.8, 130.6, 130.0,
128.9, 126.5, 123.0, 114.2, 101.8, 55.3, 51.6, 41.5; HRMS (ESI)
m/z Calcd for C16H14BrNOSeNa [M+Na]+: 417.9322; Found:
417.9317.
9
Procedure of gram scale synthesis of compound 4c: A
RB flask equipped with magnetic stir bar was charged with
10
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60
Ru(bpy)3(PF6)2 (79 mg,
2
mol%), 4-methoxybenzene
1-(2-(4-Bromophenyl)-1-selenocyanatoethyl)-2-chloro
benzene (5c). Pale yellow solid; mp: 129 – 131 °C; 46% yield
(37 mg); Rf value = 0.5 [EtOAc:petroleum ether = 1:9 (v/v)];
1H NMR (500 MHz, CDCl3) δ (ppm): 7.51 (d, J = 8.1 Hz, 1H),
7.42 – 7.39 (m, 3H), 7.33 (td, J = 7.6, 1.0 Hz, 1H), 7.27 (ddd, J =
7.6, 5.7, 1.6 Hz, 1H), 7.07 (d, J = 8.3 Hz, 2H), 5.11 (t, J = 7.9 Hz,
1H), 3.56 (dd, J = 7.9, 2.4 Hz, 2H); 13C{1H} NMR (101 MHz,
CDCl3) δ (ppm): 136.2, 136.2, 133.5, 131.9, 130.7, 130.2,
129.9, 128.1, 127.6, 121.4, 101.3, 47.3, 40.9; HRMS (ESI) m/z
Calcd for C15H15BrClN2Se [M+NH4]+: 416.9262; Found:
416.9260.
diazonium tetrafluoroborate 2c (1.02 g, 4.6 mmol) and
degassed acetonitrile (46 mL). The flask was sealed with a
septum, before 4-tert butyl styrene 1v (1.68 mL, 9.2 mmol)
and ammonium thiocyanate (1.05 g, 13.8 mmol) were added
to it. Then the orange reaction mixture was degassed with
argon and irradiated at rt with a 12W blue LED bulb at a
distance of app. 8 cm for 6h. A high-speed fan was used to
maintain the temperature. After the reaction was complete,
the mixture was filtered through a short pad of silica gel and
eluted with Et2O (200 mL). The solution was concentrated
and the residue was purified by column chromatography on
silica gel (EtOAc in petroleum ether) to afford the
corresponding product 4c (1.03g, 69%).
Synthesis of (2-([1,1'-Biphenyl]-4-yl)-1-(4- (tert-butyl)
phenyl) ethyl) (trifluoromethyl) sulfane (6). In a 25 ml RB
flask with a magnetic stir bar were charged 4d (74 mg, 0.2
mmol), CH3CN (3 ml) and Cs2CO3 (130 mg, 0.4 mmol). Then
TMSCF3 (59 μL, 0.4 mmol) was added at once to the ice-cold
reaction mixture and the resulting mixture was stirred at
ambient temperature for 2 h. The crude mixture was filtered
through a short pad of celite and extracted with DCM (3 × 5.0
mL). The resulting organic phage was washed with water (10
mL) and brine (10 mL). The organic layer was dried over
anhydrous Na2SO4 and concentrated in vacuo. The residue
was purified by silica gel column chromatography (230-400
mesh) using EtOAc/petroleum ether as eluent to afforded the
corresponding products 6 (52 mg, 63%) as pale-yellow liquid.
Rf value = 0.5 [EtOAc:petroleum ether = 1:19 (v/v)]; 1H NMR
(400 MHz, CDCl3 ) δ 7.57 (d, J = 7.4 Hz, 2H), 7.48 – 7.41 (m,
5H), 7.33 (d, J = 8.2 Hz, 2H), 7.20 (d, J = 8.3 Hz, 2H), 7.10 (d, J =
8.0 Hz, 2H), 4.56 (t, J = 7.6 Hz, 1H), 3.37 – 3.28 (m, 2H), 1.32 (s,
9H); 13C{1H} NMR (101 MHz, CDCl3) δ 151.0, 140.7, 139.6,
135.1, 131.5 (q, J = 308 Hz), 129.6, 128.7, 127.3, 127.2 126.9,
126.3, 125.1, 50.7, 42.9, 34.5, 31.3; 19F NMR (471 MHz, CDCl3)
δ -39.69 (s, 3F); HRMS (ESI) calcd for C25H25F3S [M]+:
414.1629; found 414.1625.
1-(2-(4-Methoxyphenyl)- 1-selenocyanatoethyl)- 2-nitro
benzene (5d). Pale yellow viscous liquid; 48% yield (35 mg);
1
Rf value = 0.3 [EtOAc:petroleum ether = 1:9 (v/v)]; H NMR
(400 MHz, CDCl3) δ (ppm): 8.01 (d, J = 8.1 Hz, 1H), 7.72 (dt, J =
15.0, 7.4 Hz, 2H), 7.52 – 7.47 (m, 1H), 7.13 (d, J = 8.5 Hz, 2H),
6.83 (d, J = 8.6 Hz, 2H), 5.21 (t, J = 7.8 Hz, 1H), 3.78 (s, 3H),
3.53 (dd, J = 7.8, 3.7 Hz, 2H); 13C{1H} NMR (101 MHz, CDCl3) δ
(ppm): 159.1, 147.5, 135.7, 134.3, 130.2, 129.5, 129.1, 128.9,
125.8, 114.4, 102.0, 55.4, 46.0, 40.7; HRMS (ESI) m/z Calcd for
C16H15N2O3Se [M+H]+: 363.0249; Found: 363.0246.
4-(2-Phenyl-2- selenocyanatoethyl)-1,1'-biphenyl (5e).
White solid; mp: 94 – 96 °C; 59% yield (43 mg); Rf value = 0.5
[EtOAc:petroleum ether = 1:9 (v/v)]; 1H NMR (500 MHz,
CDCl3) δ (ppm): 7.56 (dd, J = 8.2, 1.1 Hz, 2H), 7.49 (d, J = 8.2
Hz, 2H), 7.42 (t, J = 7.6 Hz, 2H), 7.38 (dd, J = 3.8, 1.6 Hz, 3H),
7.36 – 7.32 (m, 2H), 7.19 (d, J = 8.2 Hz, 2H), 4.88 (t, J = 7.9 Hz,
1H), 3.60 (dd, J = 7.8, 3.2 Hz, 2H); 13C{1H} NMR (101 MHz,
CDCl3) δ (ppm): 140.5, 140.2, 138.4, 136.5, 129.5, 129.2,
129.0, 128.8, 127.8, 127.4, 127.0, 102.3, 52.2, 42.3; HRMS
(ESI) m/z Calcd for C21H17NSeNa [M+Na]+: 386.0424; Found:
386.0416.
2,2,2-Trifluoroethyl-3-(4-methoxyphenyl)-2-
selenocyanato propanoate (5f). Pale yellow viscous liquid:
45% yield (33 mg); Rf value = 0.3 [EtOAc:petroleum ether =
1
1:9 (v/v)]; H NMR (400 MHz, CDCl3) δ (ppm): 7.14 (d, J = 8.6
Synthesis of (Z)-3-((1-(4-(Tert-butyl) phenyl)-2-(4-
methoxyphenyl) ethyl)thio)-3-phenylacrylonitrile (7). In a 15
ml reaction tube with magnetic stir bar under argon
atmosphere were charged Pd(PPh3)4 (24 mg, 10 mol%),
toluene (2 ml), phenyl acetylene (44 µl, 0.4 mmol) and 4c ( 65
mg, 0.2 mmol). The reaction mixture was degassed with argon
for 10 min. The pressure tube was sealed and heated at 120 C
for 48 h. After completion of reaction, the crude mixture was
filtered through Celite bed and concentrated in vacuo. Then
the resulting mixture was purified by silica gel column
chromatography (230-400 mesh) using EtOAc/petroleum
ether as eluent to afforded the corresponding product 7 (71
Hz, 2H), 6.86 (d, J = 8.6 Hz, 2H), 4.53 (qd, J = 8.2, 2.3 Hz, 2H),
4.14 (dd, J = 8.1, 7.1 Hz, 1H), 3.79 (s, 3H), 3.35 (ddd, J = 21.5,
14.5, 7.6 Hz, 2H); 13C{1H} NMR (101 MHz, CDCl3) δ (ppm):
168.3, 159.3, 130.2, 127.6, 122.5 (q, J = 276 Hz), 114.4, 99.2,
61.5 (q, J = 37 Hz), 55.3, 45.0, 37.2; 19F NMR (376 MHz, CDCl3)
δ -73.4 (s, 3F); HRMS (ESI) m/z Calcd for C13H12F3NO3SeNa
[M+Na]+: 389.9833; Found: 389.9836.
Tert-butyl-3-(4-methoxyphenyl)-2-selenocyanato
propanoate (5g). Pale yellow viscous liquid: 34% yield (23
1
mg); Rf value = 0.6 [EtOAc:petroleum ether = 1:9 (v/v)]; H
NMR (400 MHz, CDCl3) δ (ppm): 7.16 (d, J = 8.7 Hz, 2H), 6.85
(d, J = 8.7 Hz, 2H), 4.09 (dd, J = 7.9, 6.6 Hz, 1H), 3.79 (s, 3H),
3.37 – 3.24 (m, 2H), 1.44 (s, 9H); 13C{1H} NMR (101 MHz,
CDCl3) δ (ppm): 168.4, 159.0, 130.4, 128.3, 114.1, 100.8, 83.8,
55.3, 48.3, 37.6, 27.8; HRMS (ESI) m/z Calcd for
C15H19NO3SeNa [M+Na]+: 364.0428; Found: 364.0426.
mg, 83%) as pale-yellow liquid. Rf value
=
0.5
[EtOAc:petroleum ether = 1:9 (v/v)]; 1H NMR (500 MHz,
CDCl3) δ (ppm): 7.43 (t, J = 7.4 Hz, 1H), 7.35 (t, J = 7.6 Hz, 2H),
7.22 (d, J = 8.3 Hz, 2H), 7.18 (d, J = 7.2 Hz, 2H), 6.95 (d, J = 8.3
Hz, 2H), 6.85 (d, J = 8.5 Hz, 2H), 6.74 (d, J = 8.6 Hz, 2H), 5.32 (s,
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1H), 4.10 (t, J = 7.6 Hz, 1H), 3.78 (s, 3H), 3.06 (ddd, J = 22.2,
1H); 13C{1H} NMR (101 MHz, CDCl3) δ (ppm): 146.6, 146.3,
140.7, 130.4, 128.5, 128.0, 126.6, 123.3, 84.1, 56.8, 44.5.
14.0, 7.6 Hz, 2H), 1.29 (s, 9H); 13C{1H} NMR (101 MHz, CDCl3)
δ (ppm): 162.5, 158.4, 150.5, 137.2, 136.7, 130.5, 130.3, 130.2,
128.8, 128.2, 127.4, 125.4, 116.8, 113.7, 97.5, 55.3, 53.9, 42.7,
34.5, 31.3; HRMS (ESI) m/z Calcd for C28H29NOSNa [M+Na]+:
450.1868; Found: 450.1866.
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ASSOCIATED CONTENT
Supporting Information
Procedure of radical trapping experiment: A culture
tube equipped with magnetic stir bar was charged with
The Supporting Information is available free of charge on
the ACS Publications website.
Additional screening data, mechanistic experimental
details, X-ray crystallographic data for product 3k, and copies
of 1H, 13C{1H} and 19F NMR spectra of all new products.
Ru(bpy)3(PF6)2 (3.5 mg,
2 mol%), 4-methoxybenzene
diazonium tetrafluoroborate 2c (45 mg, 0.2 mmol) and
degassed acetonitrile (2 mL). The tube was sealed with a
Teflon screw cap, before 4-tert butyl styrene 1v (73 L, 0.4
mmol), ammonium thiocyanate (46 mg, 0.6 mmol) and
TEMPO (94 mg, 0.6 mmol) were added to it. Then the orange
reaction mixture was degassed with argon and irradiated at rt
with a 12W blue LED bulb at a distance of app. 8 cm for 6h. A
high-speed fan was used to maintain the room temperature.
After 6h, the reaction mixture was analysed by GC/MS.
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AUTHOR INFORMATION
Corresponding Author
* E-mail: smaity@iitism.ac.in
Notes
Any additional relevant notes should be placed here.
Procedure of radical clock experiment: A culture tube
equipped with magnetic stir bar was charged with
Ru(bpy)3(PF6)2 (3.5 mg,
2 mol%), 4-methoxybenzene
ACKNOWLEDGMENT
diazonium tetrafluoroborate 2c (45 mg, 0.2 mmol) and
degassed acetonitrile (2 mL). The tube was sealed with a
Teflon screw cap, before -cyclopropyl-4-chlorostyrene 10
(62 L, 0.4 mmol), and ammonium thiocyanate (46 mg, 0.6
mmol) were added to it. Then the orange reaction mixture
was degassed with argon and irradiated at rt with a 12W blue
LED bulb at a distance of app. 8 cm for 6h. A high-speed fan
was used to maintain the room temperature. After the
reaction was complete, the mixture was filtered through a
short pad of silica gel and eluted with Et2O (10 mL). The
solution was concentrated and the residue was purified by
column chromatography on silica gel (EtOAc in petroleum
ether) to afford the corresponding product 11.
1-Chloro-4-(1-(4-methoxyphenyl)-5- thiocyanatopent-2-
en-2-yl) benzene (11). Pale yellow viscous liquid; 61% yield
(42 mg); Rf value = 0.3 [EtOAc:petroleum ether = 1:9 (v/v)];
1H NMR (400 MHz, CDCl3) δ (ppm): 7.25 – 7.22 (m, 4H), 7.02
(d, J = 8.5 Hz, 2H), 6.77 (d, J = 8.6 Hz, 2H), 5.85 (t, J = 7.3 Hz,
1H), 3.81 (s, 2H), 3.74 (s, 3H), 3.02 (t, J = 7.1 Hz, 2H), 2.76 (q, J
= 7.2 Hz, 2H).; 13C{1H} NMR (101 MHz, CDCl3) δ (ppm): 158.2,
141.2, 140.7, 133.2, 130.7, 129.1, 128.6, 127.8, 125.5, 114.1,
112.2, 55.3, 35.2, 33.8, 29.4; HRMS (ESI) m/z Calcd for
C19H18ClNOSNa [M+Na]+: 366.0695; Found: 366.0692.
Procedure of nucleophilic trapping experiment: A
culture tube equipped with magnetic stir bar was charged
with Ru(bpy)3(PF6)2 (3.5 mg, 2 mol%), 4-nitrobenzene
diazonium tetrafluoroborate 2b (47 mg, 0.2 mmol) and
degassed acetonitrile (2 mL). The tube was sealed with a
Teflon screw cap, before styrene 1a (46 L, 0.4 mmol), and
MeOH (0.5 mL) were added to it. Then the orange reaction
mixture was degassed with argon and irradiated at rt with a
12W blue LED bulb at a distance of app. 8 cm for 6h. A high-
speed fan was used to maintain the room temperature. After
the reaction was complete, the mixture was filtered through a
short pad of silica gel and eluted with Et2O (10 mL). The
solution was concentrated and the residue was purified by
column chromatography on silica gel (EtOAc in petroleum
ether) to afford the corresponding product 12.
We are grateful to SERB, India (ECR/2016/000270), DST-
INSPIRE (IFA 13-CH-90) and IIT(ISM) Dhanbad for financial
support. The authors thank Prof. H. P. Nayek, IIT(ISM) for
helping in X-ray crystallographic solution. IH & SRC thank
DST-INSPIRE and IIT(ISM) Dhanbad for their research
fellowships respectively. The authors also acknowledge SAIF-
Panjab University, CSS-IACS Kolkata, CIF-BIT Mesra for
accessing analytical facilities and DST-FIST, New Delhi for
providing NMR facility at our department.
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