This is the peer reviewed version of the following article: Chem. Eur.J. 2015, 21, 18779 –18784, which has been
published in final form at http://onlinelibrary.wiley.com/doi/10.1002/chem.201503987/abstract. This article may be
used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."

Hypervalent Activation as Key Step for Dehydrogenative ortho CC Coupling of Iodoarenes
Yichen Wu,[a] Ismael Arenas,[a] Lewis Broomfield,[a] Eddy Martin[a] and Alexandr Shafir*[a]
Dedication ((optional))
Abstract: Building on earlier results, we report here a direct metalfree a-arylation of substituted cyclic 1,3-diones using ArI(O2CCF3)2
reagents; unlike other arylative approaches, the arylated products
which retain the iodine substituent ortho to the newly formed C-C
bond. The mechanism was explored using DFT calculation showing a
vanishingly small activation barrier for the C-C bond-forming step. In
fact, taking advantage of an efficient in situ hypervalent activation, the
iodoarenes are shown to undergo a cross-dehydrogenative C-C
coupling at the C-H ortho to the iodine. When using Oxone® as
terminal oxidant, the process was found to benefit from a rapid initial
formation of the hypervalent ArI(OR)2 species and the sulphateaccelerated final coupling with a ketone. The method complements
the ipso-selectivity obtained in the metal-catalysed α-arylation of
carbonyl compounds..

Introduction
Carbonyl compounds bearing an α-aryl group are important
targets in a wide range of chemical applications. Although their
preparation is possible via the conventional S NAr reaction of
enolates,[1] the α-arylation approach became particularly practical
in the late 90’s with the introduction of efficient metal-catalyzed CC coupling protocols. [2-3] Alternatively, the uncatalysed arylation
using diaryliodonium or aryllead species has also been applied in
the synthesis of α-arylketones,[4-6] Despite all these advances,
challenges remain, particularly with respect to the selectivity and
to the transfer of the ortho-substituted aryl fragments.
Our group recently reported an alternative metal-free αarylation strategy employing phenyliodine bis(trifluoroacetate)
(PIFA) as the aryl source.[7] The reaction produced arylketones
bearing the iodine atom at the ortho position of the aromatic ring
(Scheme 1). The reaction exemplifies an unusual case of
aromatic CH functionalization where the outcome was
rationalized by a [3,3] rearrangement of an intermediate iodonium
O-enolate. This new dehydrogenative cross-coupling was
compatible with a range of the ArI(O2CCF3)2 reagents,[8] and the
retention of the iodine atom in the coupling products provided
access to hindered ortho-substituted α-arylketones and
heterocycles. Notably, the method was particularly suitable for the
formation of the α-(2-iodoaryl) cyanoketones, a compound class
relevant in several applications, including drug design [9] (e.g.

[a]

Y. Wu, I. Arenas, L. Broomfield, E. Martin and A. Shafir
Institute of Chemical Research of Catalonia (ICIQ)
The Barcelona Institute of Science and Technology
Av. Països Catalans 16, 43007, Tarragona, Spain.
E-mail: ashafir@iciq.es
Supporting information for this article is given via a link at the end of
the document.((Please delete this text if not appropriate))

Levocabastine, an antihistamine) and crop protection, with
several powerful miticides (e.g. Cyflumetofen, Cyenopyrafen,
IKA-2002) based on an α-aryl-2-cyanoketone core.[10]

Scheme 1. The α-arylation employing λ3-iodanes as aryl transfer agents.

Regarding this methodology, however, an array of questions
remained concerning the mechanism, then applicability to other
challenging or industrially relevant substrate families, and as to
the potential for a more convenient protocol. Thus, we began by
investigating the metal-free formation of 2-aryl-1,3-diones. The
synthesis of such species has drawn an extraordinary amount of
synthetic effort, especially given that several major commercial
pesticides (spirotetramat, pinoxaden, spirodicyclophen) all feature
an ortho-substituted aryl group at the intercarbonylic position. [11]
Interestingly, the metal-catalysed α-arylation of cyclic 1,3diketones has met with difficulty when using ortho-substituted aryl
groups (or when forming quaternary C centres), which explains a
frequent usage of stoichiometric Ar-Pb species.[12] In this context,
we set out to explore the possibility of using mono-aryl
hypervalent iodine reagents under metal-free conditions.

Results and Discussion
Arylation of cyclic diones. Initial tests were conducted by
exposing the 2-methyl-1,3-cyclohexanedione, 1a, to PIFA (1.25
equiv). For the 1:1 CH3CN/CF3CO2H solvents mixture the
expected ortho-iodo aryl product 2a formed in 50% yield (Table 1,
entry 1). The nitromethane/trifluoroacetic acid combination was
also identified as a promising medium, especially in the presence
of small amounts (approx. 0.4 equiv) of the trifluoroacetic
anhydride (entries 2-4). Although the role of TFAA remains
unclear, it may act as a drying agent; indeed, the addition of
water to the mixture proved detrimental. Under the optimised
reaction conditions the target 2-(2´-iodophenyl)-2-methyl-1,3cyclohexanedione, 2a, was isolated in 65% yield; a similar yield
was also obtained for the dimedone-based product 2a’ (Table 2).
The presence of larger 2-alkyl substituents, including ethyl, nbutyl and benzyl, was also tolerated, affording the target α-(2iodophenyl)-1,3-diketones 2b-d. The introduction of substituted
iodoaryl groups was achieved with additional ArI(O 2CCF3)2
reagents[13,7] to give 2e-i bearing the 2-iodo-5-carboxy-phenyl,

Table 1. Optimization of the arylation of 1a with PIFA[a]

Entry

%Yield[b]

Solvent

Additive (equiv)

1

CH3CN + CF3COOH

-

50

2

CH3NO2 + CF3COOH

-

55

3

CH3NO2 + CF3COOH

(CF3CO)2O ) (1.250)

59

4

CH3NO2 + CF3COOH

(CF3CO)2O (0.375)

65

[a] 1 mmol of 1 and 1.25 mmol of 2a in 4 mL of solvent (1:1 mixture) for 5h at
room temp.[b] % isolated product.

2-iodo-3-methyl-phenyl or the potentially versatile 2-iodo-5bromophenyl moieties. The method was suitable for the 5membered cyclic diketones (products 3a-d), whereby the
arylation of 1,3-cyclopentanedione on a 5 mmol scale led to 75%
yield (1.17 g) of 3a as microcrystalline solid.

Scheme 2(A) for the 3a. Thus, a C=C bond was readily installed
by treatment with CuBr2 in MeOH,[17] affording either the 2-aryl-2methylcyclopenten-1,3-dione 4 (76%) or its 4-bromo derivative 5
(67%) depending on the amounts of the copper salt employed.
Under basic conditions 3a was opened into the 4-ketoacid 6 (90%
yield) bearing an intact 2-iodophenyl fragment. Interestingly, the
same reaction in the presence of catalytic CuI-Fe2O3 afforded
84% yield of the 3-methyl-benzofuran-based acid 7, likely via an
initial Cu-catalysed C-O coupling (intramolecular enolate
arylation[18]), followed by a base-promoted ring opening. It is of
note that the formation of 6 from 3a, and ultimately, from 2-Me1,3-cyclopentanedione highlights the ability of such cyclic 1,3diones to act as convenient synthons of a formal 1,4-dicarbonyl
dipole, as seen in Scheme 2(B). A related concept was recently
exploited by Cramer et al in the synthesis of functionalised
allenes.[19]

Table 2. The scope of the arylation reaction.[a]

Scheme 2. Examples of the synthetic versatility of 3a.

[a] Conditions: 1 mmol of diketone, 1.25 mmol of 2, 4 mL of MeNO2:TFA (1:1), rt,
5h. Yields of isolated products. [b] MeCN instead MeNO2 and without TFAA.

Attempts to engage the parent 2H 1,3-cyclohexanedione led
instead to the corresponding iodonium ylide. [15] Nevertheless, the
introduction of of a 2-allyl group allowed for the formation of the
“masked” arylated species 2j which was then deprotected to the
free 2k via a metal-catalysed deallylation reported by Kotora et
al.[16] Although the original protocol dealt with solely with 2allylmalonates, exposing 2j to Et3Al (2 equiv) and catalytic
RuCl2(PPh3)3 yielded 66% of 2j in 66% after 18h (Scheme 2),
while switching to the NiCl2(PPh3)2 catalyst accomplished this in
an 88% yield in just 90 min.[16b] The structure of the newly
generated α-aryl-1,3-diones 2 and 3 should allow for their
straightforward conversion into a variety of targets, as shown in

Mechanistic insights. As early as 1988, Oh and co-workers
postulated the possibility of a [3,3] rearrangement to explain the
appearance of 2-allyl-iodobenzene when attempting an umpolung
aromatic allylation using (PhIO)n as an oxidant, and the process
received full attention from the laboratories of Ochiai et al. in the
course of the synthesis of a series of ortho-propargyl
iodoarenes.[20] Further mechanistic studies were conducted by
Norton and co-workers, and the reaction was later applied by Zhu
et al. in a versatile approach to allyliodoarenes.[21] A series of
ostensibly closely related CH functionalization via [3,3]
rearrangement processes have also been reported for
arylsufoxides by the groups of Maulide and Procter.[15b, 22]
Focusing, once again on the mechanism of the (2-iodoaryl)
transfer, our failure to observe the putative iodonium enolate
intermediates suggested that the rearrangement step might, in
fact, be rather fast.[23] In order to shed further light on this process,
the mechanis m was probed by DFT calculations applying the
B3LYP/6-31+G(d,p) and augmented LAN2DZ (for I) combination.
In particular, it was crucial to validate the feasibility of the key
putative iodonio-[3,3] rearrangement step. Using the arylation of
the 2-cyanocyclohexanone as model system, we began by
locating the corresponding iodonium O-enolate precursor.

Figure 1. DFT reaction profile using Gaussian09 B3LYP/6-31+g(d,p) (C,H,N,O) and LAN2DZ augmented by p and d for Iodine. Solvent (CH3CN) was included with
SCRF PCM model. For the sake of clarity, the requisite TFAH and TFA- have been omitted from the profile drawing (but included in the energy calculations).

Thus, the cationic [PhI-enol]+ (A) resides 3.5 kcal/mol above
the precursors, with one of its the chair-like conformers (~ 1
kcal/mol above the open form) pre-arranged for the [3,3]
transition state (Figure 1, TS, 1 imag. frequency). This transition
state gave rise to the protonated intermediate C at -7.1 kcal/mol
which yields the final (2-iodophenyl) product 8a upon
deprotonation. The overall reaction was found to be exergonic by
56 kcal/mol. Although the C-enolate B lies 13 kcal/mol lower than
the O-enolate, we believe that the key C-C bond formation occurs
faster than the A-to-B tautomerization. Importantly, the activation
barrier for the “neutral” pathway involving the TFA-bound A (see
TS’) was found to be 12 kcal/mol higher than for the cationic A, in
line with the idea of the charge-accelerated rearrangement.[23] For
comparison, the activation barrier for a related iodonium-based
ortho-allylation[20a] was also computed. In this case, the reaction
was proposed to proceed through an Ar-I(allyl)+ intermediate. A
chair-like cationic transition state was now located with an
activation barrier of 8 kcal/mol, which was further reduced to 4
kcal/mol for the ArI fragment substituted with a –OMe group para
to the activated CH position, in light with documented the
favourable reactivity at the position para to an electron-donating
group.[21b] A significantly higher barrier of 32 kcal/mol was
calculated at the same DFT level for the classical Claisen
rearrangement of the O-allyl phenol. The vanishingly small
activation barrier in the rearrangement step of the iodonium Oenolate A is in line with the slow step in the process actually
being the ligand exchange leading to this interemediate.
The sulfate effect and the direct usage of ArI. Interestingly, the
reaction was found to be susceptible to acceleration by simple
sulphate salts. A control experiment using PIFA and 2cyanocyclohexanone using 0.5 equiv of K2SO4 reached a 64%
completion after 15 min, reaching completion in 60 min (Scheme
3A). Although the possibility of an iodonium sulphate intermediate
was considered, no evidence for such species was obtained by
1
H NMR upon stirring a solution of PIFA with K2SO4 (see Support.
Info). While the exact mechanism is still unclear, its effect can
also be seen in the arylation of the challenging open-chain 2acetylpropionitrile, reducing the reaction time from 7 days to just
18h at room temp. (Scheme 3B).
Such sulphate-promoted acceleration suggests the possibility of
using iodoarenes directly in the presence of Oxone. Here, the
process would rely on rapid in situ conversion of ArI to
ArI(O2CCF3)2 and a fast subsequent C-C coupling. Indeed, the
heat flow profiles for the oxidation of several iodoarenes with
Oxone in a CHCl3/CF3CO2H mixture revealed that the formation

of ArI(O2CCF3)2 was complete within 10-15 min (for a
representative profile, see Supporting Info), leading to nearly
quantitative formation of the hypervalent reagent.

100%
80%
60%

40%
20%
0%
0

60

120

180

Scheme 3. Effect of K2SO4 on the arylation of cyanoketones.

Next, a reaction between iodobenzene and 2cyanocyclohexanone employing Oxone® in a CH 3CN/CF3COOH
mixture afforded approximately a 50% yield of the target 2-cyano2-(2-iodophenyl)cyclohexane, 8a (Table 3, entries 1-2).[24] An
improvement was seen by replacing acetonitrile by other polar
solvents (entries 3-6), reaching an 82% yield of 8a in a DCE–
trifluoroacetic acid mixture (entry 6). Tracing the reaction
progress showed the coupling in the presence of Oxone to be
complete after just 1h, while 4h were required for m-CPBA
(entries 7-9). Lending evidence for a non-radical mechanism, the
addition of TEMPO had no appreciable effect on the outcome,
both under present conditions or using pre-formed PIFA.[25]
Essay with several iodoarenes led to a general protocol
involving an initial of 1.6 equiv of the oxidant, followed by an
additional 0.5 equiv after 2h. Thus, we set out to explore whether
the direct protocol would deliver the previously synthesized αarylcyanoketones now directly from the corresponding ArI, and,
especially, whether coupling could now be performed with
iodoarenes for which the corresponding λ3-iodane is either
unknown or expected to be unstable. As seen in Table 4, a
second halogen substituent (F, Br, Cl) was well tolerated
(products 8b-e). Iodoarenes with p-Me, CH2OH, CHO and CO2Me
substituents underwent smooth coupling (entries 8g-j), as did oiodotoluene (entry 8k) circumventing the need for the unknown
alcohol- and aldehyde-bearing hypervalent species.

Table 3. Coupling between PhI and 2-cyanoketone.[a]

Entry

Oxidant

Solvent

%Yield[b]

1

Oxone

CH3CN + acetic acid

25

2

Oxone

CH3CN + CF3COOH

52

3

Oxone

DCM + CF3COOH

84

4

Oxone

CH3NO2 + CF3COOH

81

5

Oxone

EtOAc + CF3COOH

80

6

Oxone

DCE + CF3COOH

86 (82)

7

Oxone

DCE + CF3COOH

(80)[c]

8

m-CPBA

DCE + CF3COOH

75[d]

9

m-CPBA

DCM + CF3COOH

the dehydrogenative α-arylation of industrially relevant substrate
classes, such as cyclic 1,3-diones. A direct metal-free coupling
between iodoarenes and 2-cyanoketones is possible via a key
hypervalent activation step shown to occur in <15 min when using
Oxone or m-CPBA as terminal oxidants. In the new protocol, the
iodine atom is left untouched, and the new C-C bond was created
at the ortho position, rendering the method complementary to the
existing ipso substitutive reactions. The DFT calculation revealed
that the putative Claisen-type rearrangement is indeed feasible,
and indeed appears to take place with a vanishingly small
activation barrier. This work also reveals that the key coupling
step (involving the ArI(O2CCF3)2) can be significantly accelerated
by K2SO4, which we expect to help couple hitherto difficult
substrate combinations.

82 (79)[d]

Table 4. Coupling between ArI and 2-cyanocyclohexanone.[a]

[a] Using 0.5 mmol PhI, 0.6 mmol cyanoketone and 0.8 mmol [Ox] in 2 mL
solvent o/n; [b] GC yield using CyCN as int. st., (% isolated); [c] 1h; [d] 4h.

Several new α-iodoaryl derivatives were now readily readily
obtained, such as those bearing the para –S(Me)O2, -NO2 and –
CF3 (entries 8l-n), the latter, for examples, in a 73% yield. The
use of the 3,5-disubstituted ArI allowed for the formation of the αarylketones 8p and 8q possessing the highly hindered quaternary
carbon centre. Such hindered quaternary centres have no
precedent in the “normal” metal-catalysed α-arylation literature,
highlighting the ability of the new method to fill the gaps left by
other approaches. As anticipated, while the easily oxidisable piodoanisol failed, the coupling the acetyl, mesyl and tosyl esters
of 4-iodophenol did afford the corresponding arylated 8r-8t (σp=
+0.31, +0.34 and +0.29 for the -OR, respectively). In addition, a
37% yield was achieved for 4-(trifluoromethoxy)iodobenzene (8u).
The scope also included the 7- and the 5-mebered cyclic
cyanoketones (products 9i, 10a, 10h) and delivered the arylated
2-cyanotetralone 11a in an 81% yield.
Oxone, therefore, appears to play a double role, serving as
the oxidant in the hypervalent activation (via KHSO 5), and as
promoter (via K2SO4) of the subsequent dehydrogenative C-C
coupling (Scheme 4). A lack of such positive sulphate effect may
also explain a more sluggish coupling when using m-CPBA,
despite the comparable rates of the initial ArI hypervalent
activation.

Experimental Section
Scheme 4. The double role of Oxone in the arylation via hypervalent activation.

Conclusions
We have demonstrated the hypervalent activation of iodoarenes,
whether prior to a reaction or in situ constitutes a powerful tool for

All arylation reactions were conducted in air using screw-top test tube
equipped with Teflon septum caps. Full experimental details are given in
the Supporting Information. The X-Ray crystallographic data for
compounds 3a, 4, 6, 7 and 10h has been deposited in the Cambridge
Structural Database.

The synthesis of 2-(2’-iodophenyl)-2-methyl cyclopentane-1,3-dione
(prod. 3a, Table 2). A 50 mL Schlenk tube was charged with with
PhI(O2CCF3)2 (2.69 g, 6.26 mmol) and a stirbar. Nitromethane (10.0 mL)
and trifluoroacetic acid (10.0 mL) were added, followed by the
trifluoroacetic anhydride (265 µL, 1.88 mmol). The resulting colorless
solution was allowed to stir for 15 min, at which point 2methylcyclopentane-1, 3-dione (0.56 g, 4.99 mmol) was added as a solid
in a single portion to give a light-yellow solution. After stirring for 4h at
room temperature, all volatiles were removed under reduced pressure.
The target arylketone 3a was obtained as white solid upon
chromatographic purification: gradient 10:1 –> 4:1 cyclohexane:EtOAc, Rf
= 0.11 (4:1 cyclohexane:EtOAc). White solid, yield: 1.17 g, 3.72 mmol,
75%.
NMR (500 MHz, CDCl3) δ 7.83 (dd, J = 7.9, 1.3 Hz, 1H), 7.52 – 7.39
(apparent td, 1H), 7.33 (dd, J = 7.9, 1.6 Hz, 1H), 7.06 (td, J = 7.7, 1.6 Hz,
1H), 3.15 – 3.01 (m, 4H, CH2CH2), 1.59 (s, 3H). 13C NMR (126 MHz,
CDCl3) δ 212.57 (C=O), 141.65 (C), 140.33 (CH), 131.07 (CH), 130.09
(CH), 128.45 (CH), 99.86 (C-I), 67.21 (Cq), 35.93 (CH2), 20.87 (CH3).
HRMS (ESI+) calcd m/z for C12H11INaO2 [M+Na]+ 336.9696, found:
336.9689. IR (ATR) ν (cm-1) 1751, 1708 (strong, C=O asym), 1460, 1410,
1164, 1070, 764.

This work was financed through grants from Fundació ICIQ,
MINECO (CTQ2013-46705-R and 2014-2018 Severo Ochoa
Excellence Accreditation SEV-2013-0319) and the Generalitat de
Catalunya (2014 SGR 1192). Financial support from CELLEX
Foundation through the CELLEX-ICIQ High Throughput
Experimentation platform is gratefully acknowledged.
Keywords: dehydrogenative C-C coupling • α-arylation •
hypervalent iodine • C-H functionalization • cross-coupling
[1]

1H

2-(2’-iodo-5-trifluoromethyl-phenyl)-2-cyanocyclohexanone (prod. 8n,
Table 4). A 10 mL tube was charged with a stirbar, Oxone (0.8 mmol),
nitromethane (1 mL) and trifluoroacetic acid (1 mL). and a stirbar. Next, 4iodobenzotrifluoride (0.5 mmol, 96% pure, 142 mg and 2oxocyclohexanecarbonitrile (0.75 mmol, 92 mg) were injected. The mixture
was allowed to stir for 2h, at which point the second portion of Oxone
(0.25 mmol) was added; the stirring was continued for an additional 2h.
The mixture was first filtered via celite and concentrated to move the
solvents and 8n was isolated by column chromatography: gradient 20:1 to
10:1 Hexane : EtOAc; Rf = 0.27 (10:1, Hexane : EtOAc). White solid, yield:
73% (144 mg).
NMR (500 MHz, CDCl3)  8.14 (d, J = 8.2 Hz, 1H), 7.60 (d, J = 2.2 Hz,
1H), 7.33 (dd, J = 8.2, 2.1 Hz, 1H), 3.13 (td, J = 13.6, 6.1 Hz, 1H), 2.752.65 (m, 2H), 2.58 (td, J = 12.9, 3.7 Hz, 1H), 2.38 (dtt, J = 14.4, 12.9, 3.9
Hz, 1H), 2.33 – 2.24 (m, 1H), 2.16 (dm, J = 14 Hz, 1H), 1.99 (qt, J = 13.3,
4.2 Hz, 1H). 13C NMR (126 MHz, CDCl3)  200.32 (C=O), 142.81, 138.46,
131.23 (q, J = 33.2 Hz, C-CF3), 126.83 (q, J = 3.6 Hz), 125.51 (q, J = 3.8
Hz), 123.67 (q, J = 272.6 Hz, CF3), 118.12 (CN), 103.84 (C-I), 59.36,
39.92, 38.89, 27.66, 22.53. 19F NMR (376 MHz, CDCl3)  63.02 ppm.
HRMS (ESI+) m/z calcd for C14H11NF3INaO [M+Na]+ 415.9730, found:
415.9744. IR (ATR) υ (cm-1) 2964, 2934, 2873, 2227 (CN), 1725 (C=O),
1326, 1179, 1129, 1073, 1015, 834.

[2]

[3]

[4]
[5]

1H

3-(3-methylbenzofuran-2-yl)propanoic acid from aryldione 3a (prod. 7,
Scheme 2). 2-(2-iodophenyl)-2-methylcyclopentane-1,3-dione (3a, 79 mg,
0.25 mmol) was dissolved in EtOH (1.5 mL). CuI (4.8 mg, 0.025 mmol),
Fe2O3 (4 mg, 0.025 mmol), and NaOH (22 mg, 0.55 mmol in 2 mL of
water) were added. The resulting red suspension was heated to 90 °C and
allowed to stir overnight in a pressure-proof reaction tube. The reaction
mixture was then cooled to rt., transferred to a separatory funnel and
washed with EtOAc (2 x 10 mL). The aqueous phase was then acidified
with 20 % HCl (aq) and extracted with CH2Cl2 (3 x 30 mL). Column
chromatography: silca gel, cyclohexane:EtOAc 10:1->1:1 (Rf = 0.19
cyclohexane:EtOAc 3:1). Colourless crystals, 43 mg, 0.21 mmol, 84%.
NMR (500 MHz, CDCl3) δ 7.45–7.42 (m, 1H, Ar), 7.40–7.36 (m, 1H, Ar
CH), 7.26–7.18 (m, 2H, Ar), 3.08 (t, J = 7.5 Hz, 2H, CH2), 2.81 (t, J = 7.5
Hz, 2H, CH2), 2.19 (s, 3H, CH3). 13C NMR (126 MHz, CDCl3) δ 178.80
(COOH), 154.07 (C), 151.59 (C), 130.30 (C), 123.63 (CH), 122.26 (CH),
119.05 (CH), 110.80 (C), 110.78 (CH), 32.46 (CH2), 21.60 (CH2), 7.97
(CH3). HRMS (ESI-) calcd m/z for C12H11O3 [M-H]- 203.0714, found:
203.0714.

[6]
[7]

[8]

[9]

[10]

[11]

1H

[12]
[13]
[14]

Acknowledgements

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FULL PAPER
Yichen Wu, Ismael Arenas, Lewis
Broomfield, Eddy Martin and Alexandr
Shafir *
Page No. – Page No.

We report a direct metal-free a-arylation of substituted cyclic 1,3-diones using
ArI(O2CCF3)2 reagents, with the arylated products retaining the C-I moiety ortho to
the newly formed C-C bond. DFT calculation showed a vanishingly small activation
barrier for the C-C bond-forming [3,3] rearrangement. Finally, simple iodoarenes
are shown to undergo a direct cross-dehydrogenative C-C coupling at the C-H ortho
to the iodine. The method complements the ipso-selectivity obtained in the metalcatalysed α-arylation of carbonyl compounds.

.

Hypervalent Activation as Key Step for
Dehydrogenative ortho C-C Coupling of
Iodoarenes