Copper-Catalyzed Trifluoromethylthiolation of Di(hetero)aryl-λ3-iodanes: Mechanistic Insight and Application to Synthesis of (Hetero)Aryl Trifluoromethyl Sulfides

Article abstract of DOI:10.1002/adsc.201500606

The direct and regioselective copper/S-Phos-catalyzed trifluoromethylthiolation of symmetrical and unsymmetrical di(hetero)aryl-λ³-iodanes has been accomplished for the synthesis of various (hetero)aryl trifluoromethyl sulfides employing readily accessible silver trifluoromethylthiolate (AgSCF₃) as nucleophilic trifluoromethylthiolating reagent. The developed transformation tolerates various functional groups like nitrile, enolizable ketone, ester, nitro and free carboxylic acid. Interestingly, the formal trifluoromethylthiolation of arenes was also achieved through integration of the synthesis of diaryl-λ³-iodanes from arenes with the trifluoromethylthiolation. Mechanistic investigations did not favor the radical formation and SET pathway. Based on the variable temperature ¹⁹F NMR spectroscopy, isolation of the most relevant catalytic intermediate, and stoichiometric studies supported the Cu(I)/Cu(III) catalytic cycle, wherein the oxidative addition of diaryl-λ³-iodanes was assisted by the silver salt.

Full text of DOI:10.1002/adsc.201500606

FULL PAPERS
DOI: 10.1002/adsc.201500606
Copper-Catalyzed Trifluoromethylthiolation of Di(hetero)aryl-l3-
iodanes: Mechanistic Insight and Application to Synthesis of
(Hetero)Aryl Trifluoromethyl Sulfides
Perumal Saravanana and Pazhamalai Anbarasana,*
a
Department of Chemistry, Indian Institute of Technology Madras, Chennai – 600036, India
E-mail: anbarasansp@iitm.ac.in
Received: June 23, 2015; Revised: August 31, 2015; Published online: November 17, 2015
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201500606.
Abstract: The direct and regioselective copper/S- thylthiolation. Mechanistic investigations did not
Phos-catalyzed trifluoromethylthiolation of symmet- favor the radical formation and SET pathway. Based
rical and unsymmetrical di(hetero)aryl-l3-iodanes on the variable temperature 19F NMR spectroscopy,
has been accomplished for the synthesis of various isolation of the most relevant catalytic intermediate,
(hetero)aryl trifluoromethyl sulfides employing read- and stoichiometric studies supported the Cu(I)/
ily accessible silver trifluoromethylthiolate (AgSCF3) Cu(III) catalytic cycle, wherein the oxidative addi-
as nucleophilic trifluoromethylthiolating reagent. tion of diaryl-l3-iodanes was assisted by the silver
The developed transformation tolerates various func- salt.
tional groups like nitrile, enolizable ketone, ester,
nitro and free carboxylic acid. Interestingly, the
formal trifluoromethylthiolation of arenes was also Keywords: aryl trifluoromethyl sulfides; copper; di-
achieved through integration of the synthesis of aryliodonium salts; salt metathesis; trifluoromethyl-
diaryl-l3-iodanes from arenes with the trifluorome- thiolation
Introduction
is highly desirable.[4] Typically, trifluoromethylthiolat-
ed arenes are prepared from aryl methyl sulfides
Fluorinated arenes are highly important in various through Swarts-type reaction involving photochemical
fields, like agrochemicals, pharmaceuticals and mate- chlorination of the methyl group followed by chlor-
rial sciences.[1] The introduction of fluorine or fluorine ine-fluorine exchange with SbF3 or anhydrous HF.[5]
containing groups, like trifluoromethyl (CF3) or tri- In addition, trifluoromethylthiolated arenes were also
fluoromethylthio (SCF3), into organic molecules often synthesized from arylthio derivatives, like thiols, disul-
alters their chemical, physical and biological proper-
ties.[2] In this context, the trifluoromethylthio group
holds a unique place due to its strong electron-with-
drawing power and high lipophilicity (pR = +1.44),[3]
which are important physico-chemical properties for
enhancing transmembrane permeation of pharma-
ceutical and agrochemical drugs. In addition, the
ꢀSCF3ꢁ group is amenable to subsequent transforma-
tions to SOCF3 and SO2CF3 (pR = +0.55) groups,
wherein the physico-chemical properties of the parent
molecule can be readily tuned. Some representative
examples of pharmaceuticals containing a trifluorome-
thylthiolated arene (ArSCF3) are shown in Figure 1.
However, trifluoromethylthiolated arenes in gener-
al do not exist in nature, hence, the development of
general and efficient methods for the introduction of
the trifluoromethylthio group onto aromatic moieties having the ꢀSCF3ꢁ group.
Figure 1. Examples of therapeutically important molecules
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Perumal Saravanan and Pazhamalai Anbarasan
[10d]
fides and thiocyanates, through the formation of the reaction of 1a with 1.1 equivalents of AgSCF3
in
À
S CF3 bond employing electrophilic/nucleophilic tri- the presence of 20 mol% of CuI in DMF at 508C af-
fluoromethylating reagents.[6]
forded the expected phenyl trifluoromethyl sulfide 2a
An alternative and most efficient method is the in 54% yield, as determined by 19F NMR (Table 1,
direct trifluoromethylthiolation of functionalized entry 1). In the absence of CuI, no trifluoromethyl-
arenes,[7] which includes aryl nucleophile and aryl thiolation of 1a was observed, which reveals the im-
electrophile-based transformations. Examples of aryl portance of CuI and its catalytic role in the present
nucleophile-based transformations are the reaction of reaction (Table 1, entry 2). Screening of other copper
electron-rich arenes[8] and aryl-metallic species[9] with catalysts did not show any profound effect on the for-
electrophilic
trifluoromethylthiolating
reagents mation of 2a (Table 1, entries 3–5). Next, the influ-
(CF3S+) or oxidative trifluoromethylthiolation with ence of various electron-rich ligands was examined.
TMSCF3 and sulfur. Aryl electrophile-based transfor- Use of 20 mol% of nitrogen-based ligands 2,2-bipyri-
mations include transition metal-catalyzed or -mediat-
ed trifluoromethylthiolation of aryl halides[10] or
Table 1. Copper-catalyzed trifluoromethylthiolation of di-
pseudo halides[6b] with nucleophilic trifluoromethylth-
iolating reagents (CF3SÀ). Although all these ap-
proaches provide a viable route for the synthesis of
aryltrifluoromethyl sulfides, the development of
a new, direct and efficient trifluoromethylthiolation
strategy is highly warranted.
phenyliodonium triflate 1a: optimization.[a]
In the past few years, diaryl-l3-iodanes have
emerged as an efficient arylating reagent in the transi-
À
À
tion metal-catalyzed C C and C heteroatom bond
forming reactions.[11] However, trifluoromethylthiola-
tion of diaryl-l3-iodanes for the synthesis of highly
important trifluoromethylthiolated arenes via direct
À
C SCF3 bond formation has not been documented.
Based on the importance of trifluoromethylthiolated
arenes and our continued interest in the synthesis of
fluorinated organic moieties,[12] we herein disclose the
direct and regioselective synthesis of aryl trifluoro-
methyl sulfides through copper-catalyzed trifluorome-
thylthiolation of diaryl-l3-iodanes, which are readily
accessible from arenes, with AgSCF3 (Scheme 1).
Entry [Cu]
(mol%)
Ligand Solvent Temp. Yield
(mol%)
[8C]
[%][b]
Results and Discussion
1
2
3
4
5
6
7
8
CuI (20)
–
–
–
–
–
–
DMF
DMF
DMF
DMF
DMF
50
50
50
50
50
50
50
50
50
50
50
54
0
29
44
16
20
46
67
66
95
63
40
9
70
Synthesis of (Hetero)aryl Trifluoromethyl Sulfides
CuBr (20)
[Cu][c] (20)
Cu(OTf)2 (20)
CuI (20)
CuI (20)
CuI (20)
CuI (20)
CuI (20)
CuI (20)
CuI (20)
CuI (20)
CuI (20)
CuI (10)
CuI (10)
At the outset of our investigation, we synthesized the
diphenyliodonium triflate[13] 1a from benzene and
iodine and utilized it as model substrate for the
copper-catalyzed trifluoromethylthiolation. The initial
L1 (20) DMF
L2 (20) DMF
L3 (20) DMF
L4 (20) DMF
L5 (20) DMF
L6 (20) DMF
L5 (20) dioxane 50
L5 (20) toluene 50
L5 (20) DCM
L5 (10) DMF
L5 (10) DMF
9
10
11
12
13
14
15
16
50
75
100
65 (42)[d]
66
[a]
Reaction conditions: 1a (100 mg, 0.22 mmol, 1 equiv.),
AgSCF3 (50 mg, 0.24 mmol, 1.1 equiv.), Cu catalyst,
ligand, DMF (1 mL), 508C, 12 h.
All yields determined by 19F NMR.
Cu(CH3CN)4BF4 was used.
[b]
[c]
[d]
Scheme 1. Synthesis of aryl trifluoromethyl sulfides.
508C.
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FULL PAPERS
dine L1 and 1,10-phenanthroline L2 gave 2a in 20% danes 1. Alkyl-substituted symmetrical diaryl-l3-
and 46% yield, respectively (Table 1, entries 6 and 7). iodane gave the corresponding product 2b in 81%
Interestingly, the presence of electron-rich phosphine yield. Sterically hindered ortho-substituted diaryl-l3-
ligands (L3–L6) showed a positive influence on the iodanes furnished products 2c and 2d in moderate
trifluoromethylthiolation of 1a (Table 1, entries 8–11, yield. Methoxy and halogenated aryl trifluoromethyl
for details, see Supporting Information).
Among the various phosphine ligands examined, corresponding symmetrical diaryl-l3-iodanes 1.
the best result was achieved with ligand L5 (S-Phos), However, the synthesis of highly electron-rich and
sulfides (2e–2i) were achieved in good yields from the
which resulted in the formation of product 2a in 95% electron-deficient aryl-containing symmetrical diaryl-
yield. Screening of solvents such as dioxane, toluene l3-iodanes 1 is rather difficult. Thus, we then moved
and DCM showed that DMF is superior other all the on to the regioselective trifluoromethylthiolation of
solvents studied (Table 1, entries 12–14). Subsequent- unsymmetrical diaryl-l3-iodanes 3. To start with, we
ly, decreasing the catalyst loading to 10 mol% gave synthesized two unsymmetrical diaryl-l3-iodanes 3a
product 2a in only 42% yield. Further increasing the and 3a’ from the corresponding arenes.[13b,14] Gratify-
reaction temperature to 758C and 1008C with ingly, the copper-catalyzed trifluoromethylthiolation
10 mol% of catalyst loading gave the product 2a in of 3a and 3a’ under the optimized conditions afforded
only 65% and 66% yield, respectively (Table 1, en- the product 2a in 90% and 62% yield with excellent
tries 15 and 16). Based on these studies, we chose the regioselectivity[15] (Scheme 3). Although both of them
following reaction conditions for exploring the gener- gave excellent regioselectivity, the best yield was ob-
ality of this trifluoromethylthiolation: 1 equivalent of tained with 3a possessing a 2,4,6-trimethylphenyl
diaryl-l3-iodanes 1, 1.1 equivalent of AgSCF3, group. Hence, further studies on unsymmetrical
20 mol% of CuI, 20 mol% of L5, DMF, 508C, 12 h.
diaryl-l3-iodanes were envisioned with a 2,4,6-trime-
With the best-optimized conditions in hand, we thylphenyl group.
studied the trifluoromethylthiolation of diphenyliodo-
nium salts having different counterions (Scheme 2). In
general, the presence of both coordinating and non-
coordinating counterions such as OTf, OTs, BF4, PF6
and SbF6 is well tolerated under the copper-catalyzed
trifluoromethylthiolation conditions to furnish the
product 2a in good to excellent yield. Next, the scope
of various symmetrical diaryl-l3-iodanes[13] was inves-
Scheme 3. Copper-catalyzed trifluoromethylthiolation of 3a
and 3a’.
tigated. As can be seen in Scheme 2, diverse substitut-
ed aryl trifluoromethyl sulfides 2 were synthesized in
good to excellent yield from symmetrical diaryl-l3-io-
Next, we studied the scope of unsymmetrical
diaryl-l3-iodanes under the optimized conditions. As
shown in Scheme 4, alkyl- and aryl-substituted phenyl
(such as 4-methyl, 2-methyl, 3,5-dimethyl, 2,5-dimeth-
yl, naphth-1-yl, 4-tert-butyl and 4-phenyl) containing
unsymmetrical diaryl-l3-iodanes 3 underwent smooth
reaction to afford the corresponding aryl trifluoro-
methyl sulfides (2b, 2j, 2k, 2c, 2d, 2l and 2m) in 80%,
52%, 63%, 75%, 54%, 87% and 81% yield, respec-
tively, with complete regioselectivity.
Readily functionalizable halogenated derivatives 2n
and 2i were also achieved in good yield. Interestingly,
more challenging and highly reactive functional
groups like nitrile, ketone, ester and nitro groups
were well tolerated under the optimized conditions to
furnish the corresponding products 2p, 2r and 2s–2v
in good to excellent yield. Among them, products 2r
and 2s were isolated in 53% and 65% yield, which are
well comparable with the measured 19F NMR yields.
The easily enolizable acetyl-containing unsymmetrical
diaryl-l3-iodane gave the product 2q in 66% isolated
yield. It is important to note that the present tri-
fluoromethylthiolation is even compatible with a free
Scheme 2. Copper-catalyzed trifluoromethylthiolation of
symmetrical diaryl-l3-iodanes 1. Reaction conditions:
1
(0.22 mmol, 1 equiv.), AgSCF3 (50 mg, 0.24 mmol,
1.1 equiv.), CuI (8.3 mg, 0.044 mmol, 20 mol%), L5 (19.5 mg,
0.044 mmol, 20 mol%), DMF (1 mL), 508C, 12 h. All yields
determined by 19F NMR based on 1.
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Perumal Saravanan and Pazhamalai Anbarasan
À
Scheme 5. Formal trifluoromethylthiolation of the C H
bond of arenes.
and subsequent reaction with AgSCF3 under the CuI/
L5-catalyzed conditions afforded the product 2aa in
good yield via the formation of diaryl-l3-iodanes
3aa[16]. Thus, the present methodology constitutes the
À
formal trifluoromethylthiolation of the C H bond of
unactivated arenes.
Mechanistic Insight
After the successful demonstration of CuI/L5-cata-
lyzed trifluoromethylthiolation of diaryl-l3-iodanes,
we investigated the possible mechanism of the devel-
oped transformation. At first, we executed the tri-
fluoromethylthiolation of 1a with radical scavenger
and radical clock probe substrate 5 to understand the
possible generation of radical species. Interestingly,
no quenching of the trifluoromethylthiolation of 1a
was observed when 1 equivalent each of TEMPO and
2,6-di-tert-butylphenol were used as radical scavenger
(Scheme 6a). Additionally, the radical clock probe ex-
periment was performed using O-allyl tethered diaryl-
Scheme 4. Copper-catalyzed trifluoromethylthiolation of un-
symmetrical diaryl-l3-iodanes 3. Reaction conditions:
(0.22 mmol, 1 equiv.), AgSCF3 (50 mg, 0.24 mmol,
1.1 equiv.), CuI (8.3 mg, 0.044 mmol, 20 mol%), L5 (19.5 mg,
0.044 mmol, 20 mol%), DMF (1 mL), 508C, 12 h. All yields
determined by 19F NMR based on 3.
3
carboxylic acid and the corresponding product 2w was
synthesized in 65% yield. Furthermore, biologically
important trifluoromethylphenyl (2o) and heterocyclic
trifluoromethyl sulfides (2x–2z) were also achieved in
good yields. Overall, due to the excellent functional
group tolerance and excellent regioselectivity
(Scheme 2 and 4), this copper-catalyzed trifluorome-
thylthiolation of unsymmetrical diaryl-l3-iodane 3 is
highly preferable compared to symmetrical diaryl-l3-
iodane 1 for the synthesis of aryl trifluoromethyl sul-
fides 2.
Since the diaryl-l3-iodanes were synthesized from
arene and iodo compounds, the one-pot conversion of
arene to aryl trifluoromethyl sulfide was envisaged
(Scheme 5). The reaction of arene
4
and
Scheme 6. a) Trapping experiment for possible radical inter-
mediate; b) radical clock probe experiment. All yields deter-
MesI(OH)OTs in trifluoroethanol (TFE) at room
temperature followed by evaporation of the solvent mined by 19F NMR.
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Copper-Catalyzed Trifluoromethylthiolation of Di(hetero)aryl-l3-iodanes
FULL PAPERS
l3-iodane 5, which afforded the normal trifluorome- tation gave an inseparable mixture of copper com-
thylthiolated product 6 in 36% yield (32% isolated plexes 8 and 9. Changing the solvent to acetonitrile,
yield) and no cyclization products 7 were detected by a polar coordinating solvent, afforded the exclusive
NMR (Scheme 6b). The reduced yield of the product formation of copper complex 8, which is possibly due
6 was due to the possible decomposition of starting to the better solubility and stability of AgSCF3. On
material and slow trifluoromethylthiolation of ortho- the other hand, reaction in dichloromethane, a less
substituted diaryl-l3-iodanes. These results suggest polar chlorinated solvent, furnished the copper com-
that the aryl radical or other possible radical species plex 9 as sole product in 85% yield (Scheme 7). The
are not involved in the reaction, hence we do not structure of copper complex 9 was unambiguously
favor the SET pathway.
confirmed by X-ray analysis.[21] Besides, copper com-
To gain further mechanistic insights, we conducted plex 8 can also be readily converted to 9 in good yield
the variable temperature 19F NMR spectroscopy with on reaction with AgSCF3 in dichloromethane, which
a mixture of CuI, AgSCF3 and L5 in DMF (Figure 2). proves the possible salt metathesis under the reaction
conditions.
Figure 2. Concentration/temperature diagram for the con-
version of AgSCF3 to (L5)CuSCF3, based on 19F NMR spec-
troscopy.
At low temperature (À408C to À208C), the salt meta-
thesis between AgSCF3 and (L5)CuI attains an equi-
librium state where ~60% of SCF3 anion was bound
to silver and 40% to ꢀ(L5)Cu’. Increasing the temper-
ature to À108C shifted the equilibrium in favor of
(L5)CuSCF3 and complete conversion to (L5)CuSCF3
was observed at 508C.[17]
Scheme 7. Synthesis of copper complexes 8 and 9.
Having achieved an efficient synthesis of copper
complexes 8 and 9, we examined their role in the tri-
Interestingly, cooling the reaction mixture back to fluoromethylthiolation of 1a. Reaction of 1a and
À408C regained the initial equilibrium state, which AgSCF3 in the presence of 0.2 equivalent of complex
proves that the salt metathesis between AgSCF3 and 8 or 9 afforded the product 2a in 90% and 87% yield,
(L5)CuI is highly temperature dependent and reversi- respectively. This reveals the possibility of complexes
ble. On the other hand, the reversibility of salt meta- 8 and 9 being catalytically active species or the resting
thesis can be arrested using a mixture of DMF and state of the catalyst (Table 2, entries 1 and 2). To our
CHCl3 as solvent (see the Supporting Information). surprise, a stoichiometric study of complex 9 with 1a
However, various attempts to establish the salt meta- without AgSCF3 furnished the product 2a in only
thesis between CuI and AgSCF3 in DMF in the ab- a just detectable amount (<5%) (Table 2, entry 3).
sence of L5 were unsuccessful. Thus, the presence of The reaction showed that the complex 9 does not
electron-rich and bulky phosphine ligands (L5) is vital react alone with 1a and an additional force is essen-
for the efficient salt metathesis of the copper complex tial, which could be the involvement of silver ion in
and to stabilize the active catalyst 9,[18] additionally, it the reaction. Next, we investigated the involvement of
might also help in successive oxidative addition and silver through the reaction of an equimolar mixture of
reductive elimination processes.[19]
complex 9 and 1a in the presence of a stoichiometric
Based on the NMR study, we envisaged the synthe- amount of AgSbF6, which furnished the product 2a in
sis of (L5)CuSCF3 9 from CuI, L5 and AgSCF3.[20] Re- 87% yield in a shorter reaction time (6 h) (Table 2,
action of an equimolar mixture of L5, CuI and entry 4). Decreasing the equivalents (to 30 mol%) of
AgSCF3 in DMF at 508C for 2 h followed by precipi- AgSbF6 also gave the product 2a in excellent yield
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Perumal Saravanan and Pazhamalai Anbarasan
Table 2. Trifluoromethylthiolation employing copper com-
plexes 8 and 9.[a]
Entry Cu complex
(X equiv.)
Silver salt
(Y equiv.)
Yield
[%][b]
1
2
3
4
5
6
8 (0.2)
9 (0.2)
9 (1)
9 (1)
9 (1)
AgSCF3 (1)
AgSCF3 (1)
–
AgSbF6 (1)
AgSbF6 (0.3)
AgSCF3 (0.3)
90
87
<5
87[c]
91[d]
86
9 (1)
[a]
Reaction conditions: 1a (100 mg, 0.22 mmol, 1 equiv.), Cu
complex (X equiv.), silver salt (Y equiv.), DMF (1 mL),
Scheme 9. Plausible mechanism.
508C, 12 h.
Yield determined by 19F NMR.
[b]
[c]
[d]
6 h.
10 h.
and CuI. Salt metathesis between (L5)CuI 8 and
AgSCF3 at elevated temperature would generate the
active copper species 9, (L5)CuSCF3. As shown in
(Table 2, entry 5). Instead of AgSbF6, AgSCF3 can Table 2 and Scheme 8, oxidative addition of diaryl-l3-
also be employed in 30 mol% to effect the expected iodanes 1/3 onto copper species 9 depends on the
transformation (Table 2, entry 6). These results favor kind of counterion present in the starting material.
the involvement of silver ion in the trifluoromethyl- Coordinating counterion, like triflate, containing 1/3
thiolation of 1a with complex 9.
require assistance of silver salt to promote the oxida-
Furthermore, to understand the involvement of tive addition to 9, on the contrary, having a non-coor-
À
silver ion, we examined the trifluoromethylthiolation dinating counterion, like SbF6 , 1/3 directly undergoes
of diaryl-l3-iodane 1C having a non-coordinating oxidative addition to complex 9 to produce the
counterion with complex 9. The reaction of an equi- copper species A. Finally, reductive elimination of
molar mixture of 1C and complex 9 in DMF at 508C aryl trifluoromethyl sulfide from A would furnish the
furnished the product 2a in 94% yield, interestingly, expected trifluoromethylthiolated product 2 along
without the presence of any silver ion (Scheme 8). with the formation of copper catalyst 8 or B to contin-
ue the catalytic cycle.
Conclusions
We have demonstrated the direct and regioselective
copper/S-Phos (L5)-catalyzed trifluoromethylthiola-
tion of symmetrical and unsymmetrical di(hetero)ar-
Scheme 8. Stoichiometric reaction of 1C with 9.
yl-l3-iodanes employing readily accessible AgSCF3 as
Thus, we concluded that the presence of a non-coordi- nucleophilic trifluoromethylthiolating reagent. The
nating counterion in the diaryl-l3-iodane 1C makes developed reaction showed wide substrate scope and
the iodonium center more electron deficient, hence tolerance to various reactive functional groups like ni-
1C could readily add oxidatively onto (L5)CuSCF3 9. trile, enolizable ketone, ester, nitro and even free car-
On the other hand, the presence of triflate (OTf), boxylic acid. In addition, the formal trifluorome-
a coordinating counterion, in the diaryl-l3-iodane 1a thylthiolation of arenes was also achieved through the
makes the iodonium center less electron deficient and one-pot generation of diaryl-l3-iodanes and subse-
thus requires the presence of silver salt to promote quent trifluoromethylthiolation. Preliminary mecha-
the oxidative addition of 1a onto (L5)CuSCF3
through the weakening of the I OTf bond.
9
nistic investigations did not support the involvement
of radicals in the reaction and thus excluded the SET
À
Based on the above studies, we postulated a mecha- pathway. Furthermore, 19F NMR studies revealed the
nism for the Cu/L5-catalyzed trifluoromethylthiola- formation of (L5)CuSCF3 9, the key catalytic inter-
tion of diaryl-l3-iodanes 1/3 (Scheme 9). The catalytic mediate, through the efficient salt metathesis between
cycle starts with the formation of (L5)CuI 8 from L5 (L5)CuI 8 and AgSCF3 at 508C. Subsequently, the
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Copper-Catalyzed Trifluoromethylthiolation of Di(hetero)aryl-l3-iodanes
FULL PAPERS
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catalytic intermediate 9 was isolated and unambigu-
ously characterized. Stoichiometric study of 9 with
1 provided valuable mechanistic information about
the possible Cu(I)/Cu(III) catalytic cycle, where the
oxidative addition of diaryl-l3-iodanes onto 9 to
Cu(III) species was assisted by a silver salt.
[6] a) N. J. W. Straathof, B. J. P. Tegelbeckers, V. Hessel, X.
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Experimental Section
Synthesis of 4-Acetylphenyl Trifluoromethyl Sulfide
2q
Diaryliodonium salt 3q (113 mg, 0.22 mmol, 1 equiv.),
AgSCF3 (50 mg, 0.24 mmol, 1.1 equiv.), CuI (8.3 mg,
20 mol%) and S-Phos (L5, 19.5 mg, 20 mol%) were added
into a 10 mL reaction tube in the glove box. To this reaction
mixture, dry DMF (1 mL) was introduced under an argon
atmosphere. The reaction mixture was kept at 508C and
stirred at the same temperature for 12 h. The reaction mix-
ture was cooled to room temperature, diluted with ether
(10 mL) and washed with water. Evaporation of the solvent
followed by column chromatography of the resultant crude
afforded the product 2q as a light yellow liquid; yield: 66%.
1H NMR (400 MHz, CDCl3, 248C): d=7.98 (d, 2H, J=
8.4 Hz, HAr), 7.78 (d, 2H, J=8.4 Hz, HAr), 2.63 (s, 3H,
CH3); 13C{1H} NMR (100 MHz, CDCl3, 248C): d=197.1 (C=
O), 138.5 (C), 135.8 (CH), 130.1 (C), 129.3 (q, J=308.5 Hz),
129.1 (CH), 26.7 (CH3); 19F NMR (470 MHz, CDCl3, 248C):
d=À45.14 (s, 3F, SCF3).
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Acknowledgements
We thank Council of Scientific & Industrial Research (CSIR)
(Project No. 02(0092)/12/EMR-II) for financial support and
Department of Science and Technology (DST) (Project No.
SR/S1/OC-48/2012) for sponsoring gas chromatography. PS
thanks CSIR for a fellowship.
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