Iodobenzene and m-chloroperbenzoic acid mediated oxidative dearomatization of phenols

Article abstract of DOI:10.1016/j.tetlet.2016.07.078

Oxidative dearomatization of 2- and 4-substituted phenols to their corresponding benzoquinone monoketals by catalytic amount of iodobenzene, and m-CPBA as a co-oxidant has been achieved via in situ generation of PhIO₂, a hypervalent iodine(V) s

Full text of DOI:10.1016/j.tetlet.2016.07.078

Accepted Manuscript
Iodobenzene and m-Chloroperbenzoic Acid Mediated Oxidative Dearomatiza-
tion of Phenols
Neha Taneja, Rama Krishna Peddinti
PII:
S0040-4039(16)30946-7
DOI:
http://dx.doi.org/10.1016/j.tetlet.2016.07.078
TETL 47940
Reference:
Tetrahedron Letters
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Accepted Date:
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25 July 2016
26 July 2016
Please cite this article as: Taneja, N., Peddinti, R.K., Iodobenzene and m-Chloroperbenzoic Acid Mediated Oxidative
Dearomatization of Phenols, Tetrahedron Letters (2016), doi: http://dx.doi.org/10.1016/j.tetlet.2016.07.078
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1
Tetrahedron Letters
Iodobenzene and m-Chloroperbenzoic Acid Mediated Oxidative
Dearomatization of Phenols
Neha Taneja and Rama Krishna Peddinti *
aDepartment of Chemistry, Indian Institute of Technology Roorkee, Roorkee-247667, Uttarakhand, India
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
Oxidative dearomatization of 2- and 4-subsituted phenols to their corresponding benzoquinone
monoketals by catalytic amount of iodobenzene, and m-CPBA as a co-oxidant has been achieved
via in situ generation of PhIO2, a hypervalent iodine(V) species. The transiently generated
orthobenzoquinone monoketals further underwent Diels–Alder reaction with various dienophiles
to furnish densly substituted bicyclo[2.2.2]octenones in high selectivities and yields. This
methodology features ready availability of reagents, cost effectiveness, safety, brevity,
selectivity, diversity and excellent yields.
Available online
Keywords:
oxidative acetalization
orthobenzoquinone monoketals
linearly conjugated dienones
bicyclo[2.2.2]octenones
Diels–Alder cycloaddition
2009 Elsevier Ltd. All rights reserved.
Introduction
A plethora of strategies11–14 for the dearomatization of arenols
have been emerged to produce these linearly and cross
As a powerful tool, the dearomatization1 of aromatic compounds
is an efficient strategy to generate highly reactive intermediates
for the facile formation of carbon–carbon, carbon–heteroatom
bonds, and to access architecturally complex scaffolds through
spontaneous cycloaddition and cascade reactions. The 2- and 4-
substituted phenols are by far the most periodically utilized
substrates for dearomatization in the presence of nucleophiles to
form respective masked o-benzoquinones (MOBs) and masked p-
benzoquinones (MPBs)2. Though the simple o- and p-
benzoquinones have high synthetic potential, they undergo
notorious reactions limiting their efficacy in organic synthesis.
Consequently, their chemistry is mainly explored by masking one
of the carbonyl functionalities in the form of MOBs and MPBs.
The benzoquinone monoketals are the molecules of wide
synthetic utility because of the presence of alkene, diene,
carbonyl, enone, dienone and allyl acetal functionalities. With
these intrinsic reactive assemblies, they undergo variety of
desirable annulation reactions such as Diels–Alder reaction,3 1,4-
additon,4 and [3 + 2] cycloaddition.5 MOBs undergo Baylis–
Hillman reaction6a and also show umpolung reactivity to access
unsymmetrical oxgyenated biaryls6b in the presence of Lewis
acids. However, the Diels–Alder reaction dominates the MOB
chemistry due to their proclivity towards it. MOBs undergo self-
dimerization via Diels–Alder cycloaddition because of their high
reactivity.7 However, this event can be successively avoided by
trapping these MOBs with various external dienophiles to
conjugated cyclohexa-2,4-dienones in the presence of appropriate
nucleophiles. Among them, hypervalent iodine(III) reagents,15
due to their mild reactivity and high stability, have proven to be
the most accustomed and valuable oxidants for dearomatization.16
In spite of being less flourished, λ5-iodanes17 such as Dess-Martin
periodane (DMP)18a, 2-iodoxybenzoic acid (IBX)18b and their
analogues documented good synthetic versatility. However,
stoichiometric use of these expensive reagents results in the co-
production of undesired iodoarenes in equimolar amount. To
circumvent these problems, in 2005, the Ochiai19a and Kita19b
independently reported iodine(I) arene-mediated catalytic
oxidations using m-CPBA as co-oxidant. After that, this concept
was reported extensively.20 Herein we present the studies on the
catalytic activity of iodine(I) arene for the dearomatization of
phenols to form bicyclo[2.2.2]octenones. The reactions are high
yielding and proceed under mild and eco-friendly conditions.
At the outset, we were with the idea of using elemental iodine in
place of hypervalent iodine(III) species such as DIB or PIFA to
oxidise guaiacol (1a) in the presence of methanol to form Diels–
Alder dimer 11 via MOB 1b. Initially, methanolic solution of
guaiacol was treated with elemental iodine and the contents were
allowed to stir at room temperature. Even after 24 h, formation of
dimer was not observed (Table 1, entry 1). To enhance the
oxidizing power of iodine, we supplemented various co-oxidants
such as K2S2O8, NaIO4, H2O2. However, the product formation
was not observed in these cases (Table 1, entries 2–4). Even the
combination of K2S2O8 and NaIO4 with iodine as a co-oxidants
proved unsuccessful (Table 1, entry 5) and the use of oxone
(KHSO5) also could not give the product 11 (Table 1, entry 6).
Gratifyingly, m-CPBA successfully works as a co-oxidant with
elemental iodine and resulted in the formation of the expected
generate
highly
stereo-
and
regio-selective
bicyclo[2.2.2]octenone scaffolds,8 which have been considered as
building blocks for the synthesis of a myriad of complex
biological active molecular ensembles (Figure 1).9,10
Corresponding author. Tel.: +91-133-228-5438; fax: +91-13227-
3560; e-mail: rkpedfcy@iitr.ac.in, ramakpeddinti@gmail.com

2
Tetrahedron Letters
dimer 11 in 60% yield (Table 1, entry 7), though m-CPBA
reaction afforded the 12a in 10 min with 93% yield (Table 2,
entry 12) and further decrease in its quantity resulted in slight
drop in the reaction rate (Table 2, entry 13).
alone was not capable for oxidation (Table 1, entry 8).
Interestingly, when iodobenzene is used in place of iodine with
m-CPBA as terminal oxidant, the Diels–Alder dimer was
obtained in remarkably improved yield of 86% (Table 1, entry 9).
With the optimized reaction conditions in hand (Table 2, entry
12), we explored the generality of this novel synthetic protocol
on a range of methoxy phenols bearing different substituents with
various dienophiles. In order to have better understanding of
reaction mechanism, we performed the oxidation and
cycloaddition reactions of MOBs using stoichiometric as well as
catalytic amount of iodobenzene. The Diels-Alder reaction of
MOBs having different functionalities with electron-deficient
dienophiles such as methyl acrylate (MA), methyl vinyl ketone
(MVK), methyl methacrylate (MMA) as well as with conjugative
dienophiles like styrene afforded the bicyclo[2.2.2]octenone
derivatives through endo addition in good to excellent yields
(Scheme 1). The in situ generated MOB 1b from the parent
methoxyphenol i.e., guaiacol (1a) was highly reactive and it
underwent self-dimerization very rapidly to furnish the dimer 11
in excellent yields up to 96% even in the presence of external
dienophiles. In contrast, the reactions of creosol (2a) furnished
the cycloadducts 12a-c in excellent yields, except in case of
styrene where the bicyclo[2.2.2]octenone 12d was isolated in
45% yield. The MOBs generated from 2-methoxyphenols bearing
electron-withdrawing groups i.e., methyl vanillate (3a) and
acetovanillone (4a) afforded the cycloadducts 13a-d and 14a-d in
acceptable to high yelds.
Table 1. Initial Optimization of oxidising agentsa,b
O
OH
O
dimerization
oxidant
OMe
O
MeO
MeO
MeOH, rt
OMe
OMe
OMe
11
1a
OMe
1b
Entry
Oxidant
I2
I2/K2S2O8
I2/NaIO4
I2/H2O2
I2/NaIO4/K2S2O8
Oxone
I2/m-CPBA
m-CPBA
Time
24 h
24 h
24 h
24 h
24 h
24 h
1.5 h
24 h
10 min
Yield (%)b
1
2
3
4
5
6
7
8
9
0
0
0
0
0
0
60
0
86
PhI/m-CPBA
a Reactions were carried out by dissolving 1a (0.5 mmol, 1 equiv) in methanol
(3 mL) followed by the addition of oxidant (1 equiv each) at 25 oC. b Isolated
yield of 11.
In order to achieve best reaction conditions, we examined both
the oxidizing systems i.e. I2/m-CPBA and PhI/m-CPBA on our
model reaction between creosol (2a) and methyl acrylate in
methanol to furnish the corresponding Diels–Alder adduct (12a).
To get the optimized reaction conditions, we performed the
reaction under various concentrations of iodine/iodobenzene and
m-CPBA using methanol as a solvent as shown in Table 2.
Initially, we treated the methanolic solution of creosol with 0.5
equiv of iodine and 1 equiv of m-CPBA at room temperature and
the desired product 12a was obtained in 50% yield (Table 2,
entry 1). Further increase in the amount of iodine did not improve
the yield (Table 2, entries 2 and 3). However, rise in m-CPBA
concentration enhanced the yield up to 76% (Table 2, entries 4–
7). Fortunately, the use of 0.5 equiv of iodobenzene instead of
iodine furnished 12a in 86% yield in 30 min (Table 2, entry 8),
although 1 equiv of iodobenzene increases the reaction rate
without any noticable increase in the yield (Table 2, entry 9).
Rise in the concentration of co-oxidant did not improve the yield
significantly (Table 2, entry 11). Much to our delight, by
lowering the concentration of iodobenzene to 30 mol% the
The reaction of methyl isovanillate (5a) with MA, MVK and
styrene provided the cycloadducts 15a,c,d in good yields,
whereas oxidation of 5a in the presence of MMA furnished
substantial amount of dimer 10 along with the Diels–Alder
adduct 15b. Methyl syringate (6a) reacted smoothly with MA,
MVK and styrene under oxidative-acetalization conditions to
afford the cycloadducts 16a,c,d in very good yields. Due to the
less reactivity of MMA, appreciable amount of dimer 20 was
formed in its reaction with 6a (Figure 1).
CO2Me
MeO
O
CO2Me
OMe
O
O
O
MeO
MeO
O
OMe
OMe
MeO
MeO
MeO
MeO
MeO2C
OMe
OMe
OMe
OMe
MeO2C
O
11
10
20
Table 2. Optimization of reaction conditionsa,b
Figure 1. Structures of dimers 10, 11 and 20.
MeO2C
I2/m-CPBA or
MeO2C
OH
O
The 4-halogen substituted MOBs 7b–9b are relatively stable
enough and resist self-dimerization. As expected the MOBs with
electron-withdrawing halogens at position 4 displayed less
reactivity as reflected in the reaction times, though their reactions
with all external dienophiles proceeded cleanly, to give the
Diels–Alder adducts 17a-c–19a-c in appreciable to very good
yields without formation of any dimers. Similarly, these 4-halo
guaiacols reacted smoothly with styrene under the reaction
conditions to afford the 4-halo adducts 17d–19d in yields up to
90% (Scheme 2).
PhI/m-CPBA
O
OMe
MeOH, rt
OMe
OMe
OMe
OMe
2a
12a
2b
I2 or PhI
(equiv)
m-CPBA
(equiv)
Time
(min)
yield
Entry
(%)b
50
1
2
3
4
5
I2/0.5
I2 /1
I2/2
1
60
15
10
10
10
1
55
1
1.5
1.7
54
65
I2/1
I2/1
66
At the success of oxidative dearomatization of 2-
methoxyphenols, next we probed the substrate scope for phenol
and p-substituted phenol. Keeping the concept of double
oxidative dearomatization of phenol to form monoketal in mind,
we oxidized phenol using 4 equiv of m-CPBA and 30 mol% PhI
in the presence of methanol and ethanol in 2–3 h and isolated the
MPBs 21 and 22 in 80 and 60% yield, respectively (Scheme 3).
After further exploration, we found a clean reaction by using only
2 equiv of m-CPBA to furnish the products 21 and 22 in similar
yields with easy work up albeit little longer reaction time of 3–4
h.
6
7
I2/1
I2/1
2
3
10
10
68
76
8
PhI/0.5
PhI/1
PhI/0.5
PhI/0.5
PhI/0.3
PhI/0.2
1.5
1.5
2
30
5
5
86
86
86
90
93
92
9
10
11
12
13
2.5
2
2
5
10
25
a Reactions were performed by sequential addition of m-CPBA to a solution
of iodine or iodobenzene in methanol (3 mL) followed by the addition of
methanolic solution (2 mL) of creosol (2a, 0.5 mmol, 1 equiv) and methyl
acrylate (10 mmol, 20 equiv) at rt. b Isolated yield of 12a.

R2
R3
R1
R3
R3
X
Y
X
Y
R3
R2
R1
O
H
H
H
H
H
H
H
R2
R1
OH
2
3
4
5
6
CH3
R2
R1
3
PhI, m-CPBA
O
CO2Me
COMe
H
OMe
MeOH, rt
CO2Me
H
OMe
OMe
OMe
OMe
CO2Me
2b6b
12a-d16a-d
2a6a
O
MeO2C
MeO2C
Ph
O
O
OMe
OMe
O
O
OMe
OMe
12a
OMe
OMe
OMe
OMe
12d
12b
12c
A/10 min, 45%
B/35 min, 55%
A/15 min, 74%
B/45 min, 74%
A/10 min, 87%
B/30 min, 87%
A/10 min, 86%
B/20 min, 93%
O
Ph
MeO2C
MeO2C
O
O
O
O
OMe
OMe
OMe
A/15 min, 85%
OMe
MeO2C
MeO2C
OMe
MeO2C
OMe
MeO2C
OMe
OMe
13b
13d
13c
A/25 min, 75%
B/45 min, 85%
13a
A/10 min, 87%
B/30 min, 92%
A/10 min, 96%
B/30 min, 96%
B/ 45 min, 85%
O
MeO2C
Ph
MeO2C
O
O
OMe
OMe
O
OMe
O
OMe
MeOC
MeOC
MeOC
OMe
OMe
OMe
MeOC
14b
14d
OMe
14c
A/30 min, 60%
B/1.5 h , 70%
A/25 min, 67%
B/50 min, 72%
14a
A/20 min, 75%
B/1 h, 80%
A/20 min, 89%
B/50 min, 89%
O
MeO2C
Ph
MeO2C
O
O
MeO2C
O
OMe
OMe
15b
MeO2C
O
MeO2C
OMe
OMe
MeO2C
OMe
OMe
OMe
OMe
15d
15c
cA/1.5 h, 41%
B/2 h, 47%
15a
A/50 min, 61%
B/1 h, 65%
A/50 min, 78%
B/1 h, 78%
A/1 h, 68%
B/1.5 h, 68%
O
MeO2C
Ph
OMe
MeO2C
OMe
O
OMe
OMe
O
O
O
OMe
OMe
MeO2C
OMe
OMe
MeO2C
OMe
MeO2C
MeO2C
OMe
OMe
16b
OMe
16d
A/50 min, 75%
B/1 h, 77%
dA/50 min, 58%
B/1.5 h, 67%
16c
A/50 min, 75%
B/1 h, 85%
16a
A/40 min, 75%
B/50 min, 80%
Scheme 1. Oxidative acetalization-Diels–Alder strategy of methoxyphenols 2a–6aa,b
aReaction conditions: Method A: a methoxyphenol (2a–6a, 1 mmol), dienophile (20 equiv), PhI (1 equiv) and m-CPBA (1.5 equiv) in methanol (5 mL) at rt.
Method B: a methoxyphenol (2a–6a, 0.5 mmol), dienophile (20 equiv), PhI (30 mol%), and m-CPBA (2 equiv) in methanol (3 mL) at rt for the given time. bYield
of isolated products. cCorresponding dimer 10 was isolated in 57% yield. dCorresponding dimer 20 was isolated in 38% yield.
Having established an efficient protocol for dearomatization of
phenol and 2-methoxyphenols, we extended this strategy by
carrying out the oxidation of 4-methoxyphenol with PhI/m-
CPBA in methanol to afford masked p-benzoquinone 21 in 86%
yield (Scheme 4). Similarly, 4-alkyl substituted phenols were
tolerates
phenyl
group
to
furnish
corresponding
cyclohexadienones 23d in 83% yield. To further evaluate the
efficacy of the present protocol, we carried out the oxidative
dearomatization of 4-substituted phenols using ethanol as an
external nucleophile to obtain the corresponding dienones 24a-d
in good yields. It turned out that the methodology shows unique
general reactivity (Scheme 4).
oxidized
to
the
corresponding
cross
conjugated
cyclohexadienones 23 and 24 in very good yields.
.Although a relatively low yield was observed in the reactions of
phenols bearing bulky isopropyl and tert-butyl group wherein the
corresponding phenol was added at 50 oC to improve the yield of
23b and 24c to 70 and 61%, respectively. The reaction also

4
Tetrahedron
X
Y
X
Y
Z
O
OH
PhI/ m-CPBA
MeOH, rt
7
8
9
Cl
Br
I
OMe
O
OMe
Z
Z
OMe
OMe
Z
OMe
17a-d-19a-d
7b-9b
7a-9a
O
Ph
MeO2C
MeO2C
Z
O
O
O
O
OMe
OMe
OMe
OMe
Z
Z
Z
OMe
OMe
OMe
OMe
A/5 h, 68%
B/3 h, 75%
A/4 h, 80%
B/3 h, 87%
17a
18a
17b
17d
Z = Cl (17)
Z = Br (18)
17c
A/4 h, 80%
B/3 h, 90%
A/4 h, 70%
B/3 h, 77%
18b A/6 h, 80%
18d
19d
18c
19c
A/5 h, 77%
B/3 h, 87%
A/5 h, 88%
B/3 h, 90%
A/5 h, 60%
B/3 h, 70%
B/3 h, 80%
A/5 h, 73%
B/3 h, 80%
19a A/4 h, 72%
19b
A/5 h, 60%
B/3 h, 75%
A/4 h, 50%
B/2 h, 65%
Z = I (19)
B/2 h, 83%
Scheme 2. Reaction of 4-halo guaiacols with olefinic compoundsa,b
aReaction conditions: Method A: a 4-halo-2-methoxyphenol (7a–9a, 1 mmol, 1 equiv), dienophile (20 mmol), PhI (1 equiv) and m-CPBA (1.5 equiv) in methanol
(5 mL) at rt. Method B: a 4-halo-2-methoxyphenol (7a–9a, 0.5 mmol, 1 equiv), dienophile (10 mmol), PhI (30 mol%), and m-CPBA (2 equiv) in methanol (3
mL) at rt for the given time. b Yield of isolated products.
undergoes [4 + 2] cycloaddition either with dienophile to afford
Diels–Alder adduct or participates in the self-dimerization event
with another molecule of MOB.
Scheme 3. Dearomatization of phenola
aReactions were performed with phenol (0.5 mmol, 1 equiv), PhI (30 mol%),
and m-CPBA (2.0 mmol) in solvent (3 mL) at rt.
In an effort to understand the course of the reaction, we
performed the reaction between iodobenzene and m-CPBA in
methanol for 10 min, then the reaction mixture was filtered to
afford a white solid which was found to be iodoxybenzene
o
(PhIO2)21a {mp: 234–235 C, IR: max 763, 737, 731, 714 cm–1,
HRMS (ESI+): m/z calcd for PhIO2Na [M+Na]+: 258.9353,
found: 258.9226}. To further support the role of PhIO2 as an
intermediate, we have prepared PhIO2 and PhIO according to the
literature procedure21b and carried out the oxidation of 2a with
these synthesized hypervalent iodine reagents. It was observed
that the reaction of 2a with PhIO2 in methanol was completed in
15 min and afforded 12a, whereas the reaction with PhIO did not
reach to completion even after 3–4 h.
Proposed mechanism for the reaction is outlined in Scheme 5.
Initially, m-CPBA oxidizes iodobenzene in situ to generate
electrophilic hypervalent iodine(V) species PhIO2. Then the
nucleophilic oxygen of phenol attacks on the electrophilic
iodine(V) centre of PhIO2 to produce species A. After the attack
of one molecule of methanol on electrophilic carbon, the species
A collapses to MOB through dearomatization accompanying the
release of water and an iodine(III) species PhIO. The latter
participates in the oxidation of arenol into another molecule of
Scheme 4. Dearomatization reactions of 4-subsituted phenolsa
MOB via species B. The influence of the nucleofugality of the
aReactions were performed with 4-substitued phenols (0.5 mmol), PhI (30
phenyliodanyl group helps the two-electron reduction of the
iodine(III) center with simultaneous regeneration of PhI which
further involves in the catalytic cycle. Thus formed MOB
b
mol%), m-CPBA (2 mmol) in solvent (3 mL) at rt. Yield of isolated
products. c Reactions done at 50 oC.

5
mmol, 2 equiv) was added followed by addition of phenol and
its p- ubstituents. The resulting yellow colour solution was stirred
at the given temperature for 2–6 h. After the completion of the
reaction, as monitored by TLC, the solvent was evaporated in
vacuo. The mixture was washed with a saturated aqueous
solution of NaHCO3 and extracted twice (2 x 20 mL) with
CH2Cl2. The combined organic layers were washed with brine,
filtered, dried over anhydrous Na2SO4 and concentrated in vacuo.
The residue was purified by silica gel column chromatography
using EtOAc (10–20%) in hexanes to afford the pure
cyclohexadienones 21–24.
Acknowledgements. This work was supported by DST [research
grant No. SR/S1/OC-38/2011], New Delhi. We thank DST for
providing HRMS facility in FIST program and NT thanks MHRD
for a research fellowship
Scheme 5. Proposed reaction mechanism
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Conclusions
In summary, we have thrived a clean and efficient protocol for
the dearomatization of phenols using catalytic iodobenzene in the
presence of m-CPBA as terminal oxidant. The in situ generated
PhIO2 readily transform 2- and 4-subsituted phenols to MOBs
and cross conjugated cyclohexadienones, respectively, and the in
situ generated MOBs underwent Diels–Alder reaction with
various dienophiles to give bicyclo[2.2.2]octenone scaffolds.
Thus we unraveled a new horizon for the generation of
benzoquinone monoketals.
2.
3.
4.
General Procedure for the Diels–Alder Reaction of MOBs 1b–9b
with dienophiles:
Method A: To a stirred solution of iodobenzene (204 mg, 1
mmol, 1 equiv) in dry methanol (3 mL) dry m-CPBA (374 mg, 2
mmol, 1.5 equiv) was added followed by addition of methanolic
solution (2 mL) of guaiacol derivatives (1 mmol). To the
resulting yellow colour solution, dienophile (20 mmol, 20 equiv)
was added and stirred the reaction mixture at room temperature
for 10 min to 5 h. After the completion of the reaction, as
monitored by TLC, the solvent was evaporated in vacuo. The
mixture was washed with a saturated aqueous solution of
NaHCO3 and extracted twice (2 x 20 mL) with CH2Cl2. The
combined organic layers were washed with brine, filtered, dried
over anhydrous Na2SO4 and concentrated in vacuo. The residue
was purified by silica gel column chromatography using EtOAc
(10–20%) in hexanes to afford the pure cycloadducts 12a-d–19a-
d.
Method B: To a stirred solution of iodobenzene (30 mol%) in
dry methanol (2 mL) dry m-CPBA (249 mg, 1 mmol, 2 equiv)
was added followed by addition of methanolic solution (1 mL) of
guaiacol derivatives (0.5 mmol). To the resulting yellow colour
solution dienophile (10 mmol, 20 equiv) was added and stirred
the reaction mixture at room temperature for 20 min to 3 h. After
the completion of the reaction as monitored by TLC, the solvent
was evaporated in vacuo. The mixture was washed with a
saturated aqueous solution of NaHCO3 and extracted twice (2 x
20 mL) with CH2Cl2. The combined organic layers were washed
with brine, filtered, dried over anhydrous Na2SO4 and
concentrated in vacuo. The residue was purified by silica gel
column chromatography using EtOAc (10–20%) in hexanes to
afford the pure cycloadducts 12a-d–19a-d. The NMR data of the
compounds from the current study is comparable with that of the
compounds reported in literature.22
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General Procedure
cyclohexadienones 21–24: To a stirred solution of iodobenzene
(30 mol%) in dry methanol (2 mL) dry m-CPBA (249 mg, 1
for
the
formation
of
2,5-

6
Tetrahedron
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Graphical Abstract
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Iodobenzene and m-Chloroperbenzoic Acid
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Mediated Oxidative Dearomatization of Phenols
Neha Taneja and Rama Krishna Peddinti *

7
Highlights of the Work
 Explored easy accessible and cost-effective iodobenzene–mCPBA reagent system.
 Dearomatization of phenols to the corresponding cyclohexadienones has been studied.
 The methodology is clean and efficient and avoids the coproduction of iodoarenes.
 Overcomes the stoichiometric amount of expensive hypervalent iodine reagents.
 Oxidation–Diels–Alder protocol furnishes bicyclo[2.2.2]octenones in high yields.