Synthesis of Dibenzofurans via C-H Activation of o-Iodo Diaryl Ethers

Article abstract of DOI:10.1021/acs.joc.5b00634

An efficient method for the synthesis of dibenzofuran from o-iododiaryl ether using reusable Pd/C under ligand-free conditions has been developed. Synthesis of o-iododiaryl ether was achieved in one pot through sequential iodination and O-arylation of phenol under mild reaction conditions.

Full text of DOI:10.1021/acs.joc.5b00634

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Article
Synthesis of Dibenzofurans via C-H Activation of ortho-Iodo Diarylethers
Niranjan Panda, Irshad Mattan, and Dinesh K. Nayak
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.5b00634 • Publication Date (Web): 04 Jun 2015
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Synthesis of Dibenzofurans via C-H Activation of ortho-
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Iodo Diarylethers
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Niranjan Panda,* Irshad Mattan and Dinesh Kumar Nayak
Department of Chemistry, National Institute of Technology Rourkela, Odisha,ꢀ769008, India,
Fax: +91 661 2462651, Tel: +91 661 2462653; Email: npanda@nitrkl.ac.in
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TOC
Abstract. An efficient method for the synthesis of dibenzofuran from orthoꢀiododiaryl ether
using reusable Pd/C under ligandꢀfree conditions has been developed. Synthesis of orthoꢀ
iododiaryl ether was achieved in oneꢀpot through sequential iodination and Oꢀarylation of
phenol under mild reaction conditions.
Keywords: Dibenzofurans; orthoꢀIododiaryl ethers; Oꢀarylation, arylꢀaryl bond formation;
CꢀH activation.
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Introduction
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The dibenzofuran nucleus is an omnipresent motif of numerous natural products and
pharmaceutical candidates that exhibit antiꢀcancer, antiꢀbacterial, antiꢀallergy, antiꢀmalarial
and antiꢀinflammatory activities.1 Dibenzofurans are also endowed as a photolabile protecting
group (caging group) in the biological process investigation.2 In addition, fused benzofuran
motifs are considered to be potential host material in blue phosphorescent organic lightꢀ
emitting diodes (PhOLEDs).3 The rising usage of dibenzofurans has spurred considerable
interest in developing new methods with enhanced scope, generality, and cost effectiveness
for their synthesis. Of the reported methods, annulation of the orthoꢀaryl phenol represents a
classical synthetic methodology4 to achieve dibenzofurans. Cyclization of the diaryl ether
through oxidative arylꢀaryl bond formation is another potential (may be more popular)
approach. Evidently, the diaryl ethers required for the later cyclization is conventionally
obtained by SNAr reaction or by transition metal catalyzed Ullman CꢀO coupling reactions;5
which are often associated with limitations such as harsh reaction conditions, high
temperature, limited substrate scope and use of molar excess of catalyst.6 In conjunction,
several pioneering efforts have been made for the cyclization of diaryl ether derivatives
(Scheme 1). For instance, photoꢀinduced annulation of orthoꢀchloronaphthyl phenyl ether
was reported by Henderson and Zweig.7 Pschorr reaction that allows the intramolecular freeꢀ
radical cyclization of diazotized orthoꢀ(ary1oxy)anilines in the presence of excess Cuꢀ
catalyst, was successfully employed to afford dibenzofurans.8 Owing to the inexpensive and
better solubility, ferrous sulphate was also potentially used to improve the yield of
dibenzofuran.9 Du and Zhou employed Pd(OAc)2 for the cyclization of orthoꢀaryl diazonium
tetrafluoroborate to afford dibenzofuran in moderate to good yield.10 Intriguingly, a Pschorrꢀ
type radical cyclization process using organoboronic acids and trifluoroborates instead of
hazardous diazonium salt in the presence of catalytic amount of silver nitrate and
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stoichiometric potassium persulfate was developed by Baran and coꢀworkers.11 Glorius et al.
prepared dibenzofurans through decarboxylative CꢀC bond formation reaction using
Pd(OTf)2/Ag2CO3 catalyst.12 Very recently, Ishida et al. exploited the oxidative coupling of
two CꢀH bonds of diaryl ethers to enable dibenzofuran by ZrO2 supported Pd(OH)2 catalyst
using molecular O2 as a sole oxidant.13 Fu and coꢀworkers transformed the
dibenzoxaborininols into dibenzofuran derivatives in good to excellent yield under palladium
catalysis in the presence of iodine.14 Beside these worthy developments, transition metal
catalyzed oxidative cyclization of orthoꢀhalo diaryl ether to dibenzofuran is relatively less
explored.7, 15 Intriguingly, Liu and Larock reported a ligand assisted Pdꢀcatalyzed route (i.e.
Pd(OAc)2/PCy3) for the coupling of orthoꢀiodophenol with the inꢀsitu generated benzyne
intermediate to accomplish dibenzofuran.15b Fagnou and coꢀworkers made an appealing effort
by employing similar catalytic system (e.g. Pd(OAc)2/PCy3) for the intramolecular
cyclization of orthoꢀchloro diaryl ether to produce dibenzofuran.15c However, they observed
that the hydrodehalogenation was a competent reaction under similar reaction conditions.
Notably, in order to inhibit the hydrodehalogenation, an equimolar amount of Ag2CO3 was
employed along with the Pdꢀcatalyst. Later, the same group used Pearlman’s catalyst
(Pd(OH)2/C) for the effective cyclization of orthoꢀiodo diaryl ether at 140°C.15d Although
these methods are promising, but the use of the expensive catalyst, ligand, and limited
substrate scope often impedes their generality to achieve dibenzofuran unit. Additionally,
multistep access of orthoꢀhalo diaryl ether garners further interest for the development of an
efficient route to access such species from the readily available phenols, and their subsequent
transformation to dibenzofuran derivatives. In continuation of our interest in the
development of novel protocols for heterocycle synthesis,16 here we report a practical and
inexpensive method for the synthesis of orthoꢀiodo diaryl ether from the readily available
phenols. Subsequently, cyclization of the same by intramolecular arylꢀaryl coupling to
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dibenzofuran derivatives was achieved by the use of less expensive, reusable Pd/C catalyst
under ligandꢀfree conditions.
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Scheme 1. Synthesis of dibenzofuran from functionalized diaryl ether
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OH
B
R
O
ref. 13
R
R
R
O
I
/
ref. 14
)
Cl
O
CO2R'
c
A
O
(
2
d
P
R
UV
R
O
R
R
ref. 12
ref. 7
R
BF3K
Cl / Br/ I
R
R
K
2S
2O8
O
O
R
R
O
Pd/C
ref. 11
R
ref. 15
+
N2
I
OH
present work
O
O
R
R
R
R
R
ref. 10
Results and Discussion
We initiated our work with a search for a suitable method for the synthesis of orthoꢀ
halo diaryl ether. Typically, transitionꢀmetal catalyzed Oꢀarylation of orthoꢀhalo phenol is
disconsolate. On the other hand, pioneering work of Olofsson has been emerged as a more
companionable protocol for the selective Oꢀarylation reaction17 by diaryliodonium
tetrafluoroborates /triflates. In contrast, use of precious diaryliodonium salt with the loss of
an equimolar amount of expensive iodobenzene impedes its large scale utility. Thus,
development of an economical and efficient method for Oꢀarylation with simultaneous orthoꢀ
halogenation is recognized to be important.
In continuing studies, we envisaged that hypervalent iodine(III)ꢀpromoted Oꢀarylation
reactions18 could be employed to prepare orthoꢀiodo diaryl ethers from the readily available
phenols. In fact, utilizing 4ꢀnitrophenol (1a) as the substrate in the presence of 1.5 equiv. of
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phenyliodine diacetate (PIDA) in acetic acid under reflux, leads to the formation of 1ꢀ(2ꢀ
iodoꢀ4ꢀnitrophenoxy)benzene (3a) in quantitative yield. However, when 4ꢀhydroxy
benzaldehyde was treated with PIDA, under similar reaction conditions 3ꢀiodoꢀ4ꢀphenoxy
benzaldehyde (3b) was obtained, albeit in poor yield (30%). In order to improve the yield, the
reaction conditions were optimized by screening the additives and solvents (Table 1). We
observed that when the reaction was carried out with PIDA in the presence of 5 equiv. of
acetic acid in dichloroethane at 80°C, 3b was obtained in 45% yield. Furthermore, changing
the additive from acetic acid to pivalic acid, the yield of the reaction was further increased to
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Table 1. Optimization of reaction conditionsa
CHO
O
I
AcO
+
OAc
I
Solvent, additive
OHC
condition, 12 h
3b
OH
1b
Entry
1
Solvent
CH3COOH
CH3CN
MeOH
DCE
Additive
ꢀꢀ
Conditions
reflux
reflux
reflux
reflux
reflux
reflux
reflux
80°C
Yield (%)
30
35
23
45
7
2
CH3COOH
CH3COOH
CH3COOH
CF3COOH
CF3SO3H
CF3SO3H
CH3COOH
PivOH
3
4
5
DCE
6
DCE
5
7
DCE
10
46
60
20
07
13
0ꢀ5
8
Toluene
DCE
9
80°C
10
11
12
13
PivOH
DCE
ꢀꢀ
80°C
CF3COOH
80°C
CF3COOH
DCE
reflux
reflux
base
aReaction conditions: 4ꢀHydroxy benzaldehyde (1b) (100 mg, 0.82 mmol), PIDA (1.5
equiv.), additive (5 equiv.) in 3 mL of solvent, heat, base: K2CO3/ Cs2CO3/ tBuOk/ NaOAc.
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60%. Use of other acids (trifluoroacetic acid, triflic acid, pꢀtoluene sulfonic acid, benzoic
t
acid) and bases (K2CO3, Cs2CO3, BuOk, NaOAc) as an additive was found to be less
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efficient. Notably, other hypervalent iodines such as PhICl2 and PhI(OCOCF3)2 were found to
be inefficient to produce 3b (0ꢀ10% yield). Thus, the optimum yield of 3b was obtained when
4ꢀhydroxy benzaldehyde was treated with 1.5 equiv. of PIDA and 5 equiv. of pivalic acid in
dichloroethane at 80°C for 12 h. Unlike, Steven’s work18a when 1a was treated with PIDA
and acetic acid in dichloroethane at room temperature for 3 days, partial conversion occurs
with the formation 3a (40% yield) and no trace of iodinium ylide i.e. phenyliodonioꢀ4ꢀ
nitrophenolate was identified (from the 1H NMR of crude reaction mixture). Gratifyingly, the
formation of analogues ether from the reaction of dimedone and PIDA was precedent in the
literature. It has been reported that such reaction proceeds through the initial formation of
iodinium ylide that undergoes subsequent phenyl migration to afford the desired ether.
Notably, Nozaki et al. suggested a fiveꢀmembered cyclic pathway for phenyl migration18b
whereas, Moriarty proposed a ligand coupling mechanism with fourꢀmembered cyclic
intermediate.18c In contrary, from DFT study, Bakalbassis proved that the intramolecular
thermal phenyl migration proceeds via a concerted mechanism through a fiveꢀmembered
cyclic transitionꢀstate (more resembles with Nozaki’s pathway) without forming any
intermediate.18d In line with the above precedence, it may be expected that our sequential
iodination and arylation takes place via a transient intermediate 2 (Scheme 2).
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Next, by using optimized reaction conditions, several orthoꢀiodo diaryl ethers (3a-p)
were prepared from the commercially available phenols bearing electronꢀwithdrawing groups
such as ꢀNO2, ꢀCN, ꢀCHO, ꢀCOCH3, ꢀCONR2, ꢀCONHR, ꢀCO2R, etc. in moderate to
excellent yield (Scheme 2). Notably, 4ꢀsubstituted phenols lead to the desired product in good
yield whereas 3ꢀsubstituted phenols lead to a mixture of iodoꢀderivatives in moderate yield.
Nevertheless, the reaction of phenol, bearing electronꢀdonating or ꢀneutral group (e.g. phenol,
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pꢀcresol, 4ꢀhydroxy anisole) did not produce any 2ꢀphenoxy aryl iodide. Thus, it may be
revealed that the presence of electronꢀwithdrawing groups in the aromatic ring that imparts a
balance between the nucleophilicity of the phenol and the electron deficiency in the ring is
responsible for the cascade iodination and Oꢀarylation process. Eventually, differently aryl
substituted hypervalent iodine reagents were also found to be useful to produce orthoꢀ
iododiaryl ethers in good yield. Thus, when pꢀnitrophenol was treated with substituted aryl
diacetates (Ar = 4ꢀchloro phenyl and 4ꢀmethyl phenyl) under optimized reaction conditions,
the corresponding orthoꢀiodo diaryl ethers 3q and 3r were produced in appreciable yield.
Scheme 2. Synthesis of orthoꢀiodo diaryl ethersa
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R'
R'
OH
O
R'
I(OAc)2
O
I+
I
PivOH (5 equiv)
ClCH2CH2Cl
80 0C, 12 h
R
R
R
1
3
2
I
CHO
I
NO2
I
I
CO2Me
COCH3
CN
O
O
O
O
3b, 60%
3a, 98%
3c, 92%
3d, 85%
I
CO2Et
I
CO2Pri
CO2But
I
I
O
O
O
O
3e, 80%
3f, 81%
3h, 71%
3g, 70%
CHO
I
CONPh2
I
CONHPh
I
I
O
CHO
O
O
O
3k
3i, 64%
3l
3j, 61%
50% (1.5:1)
CN
COCH3
I
I
I
I
O
O
3n
CN
COCH3
O
O
3m
48% (2:1)
3o
3p
40% (1.8:1 )
inseparable mixture
Cl
I
NO2
Me
I
NO2
O
O
3q, 62%
3r, 60%
a Reaction conditions: Phenol 1 (100 mg), ArI(OAc)2 (1.5 equiv.), PivOH (5 equiv.) in 3 mL
of dichloroethane, 80°C.
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Having a series of orthoꢀiododiaryl ethers (3), next we sought to investigate the
annulation reaction to produce dibenzofuran derivatives. For the initial screening, 3ꢀiodoꢀ4ꢀ
phenoxybenzonitrile (3c) was taken as a model substrate and treated with various palladium
catalysts and 3 equiv. of potassium carbonate in N, N-dimethylacetamide (DMA) at 140°C
for 12 h. When 5 mol% of palladium acetate was used, the intramolecular cyclization as well
as hydrodehalogenation occurs and a mixture of dibenzofuran (6c) and hydrodehalogenated
product (7) was produced (9:1 mixture from 1H NMR). Reducing the Pd(OAc)2 concentration
from 5 mol% to 0.5 mol% also furnish the same result. We observed that PdCl2, Pd(PPh3)4
were also produce the dibenzofuran 6c in DMA in the presence of 3 equiv. of K2CO3 (~ 90%
yield) along with the inseparable byproduct 7 (from GC analysis). Change of catalyst to
heterogeneous catalyst such as 3 mol% of Pd (10 wt %) on activated charcoal support19 also
furnish the similar result. It may be noted that both the dibenzofuran (6c) and
hydrodehalogenated product (7) have same Rf value and are obtained as an inseparable
mixture. In order to hinder the hydrodehalogenation reaction, several attempts have been
made with the different combination of catalyst, base, and solvent at different temperatures
(Table 2). Among the various tested bases, NaOAc was found to be more appropriate to
produce only 6c in the presence of Pd/C catalyst. Under controlled experimentation, when the
reaction was carried out in the absence of the catalyst, the hydrodehalogenation product (e.g.
7) was formed (Table 2, entry 16). Among the tested solvents dimethylacetamide (DMA)
affords the product 6c in highest yield (95%); whereas other solvents like THF, EtOH,
DMSO, DMF etc. did not furnish 6c in appreciable yield. It may be expected that DMA
served as both solvent and chelating agent for the catalyst to produce 6c. Nevertheless,
lowering of temperature from 140°C to 100°C could not produce 6c even after a prolonged
period (36 h). In the absence of the base, about 30% conversion occurs even after 24 h. After
several experimentations, we observed that 0.3 mol % of Pd/C is equally potent to produce 6c
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quantitatively (95% yield) over a period of 16 h with excellent selectivity for arylation over
hydrodehalogenation reaction.
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Table 2. Optimization of the reaction conditionsa
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CN
I
CN
CN
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[cat.] / base
Solvent, heat,
16 h
O
O
O
3c
6c
7
Entry
Catalyst
Base
Solvent
Yield%, (6c:7)
1
Pd(OAc)2
PdCl2
Pd(PPh3)4
Pd/C
K2CO3
K2CO3
K2CO3
K2CO3
Cs2CO3
DMA
DMA
DMA
DMA
DMA
DMA
DMA
DMA
DMA
DMF
DMSO
DCE
90 (9:1)
89 (9:1)
90 (9:1)
90 (9:1)
90 (8:2)
90 (9:1)
92 (9:1)
95 (8:2)
95 (1:0)
35 (1:0)
45 (1:0)
n. r.
2
3
4
5
Pd(OAc)2
Pd(OAc)2
Pd/C
6
NaHCO3
NaHCO3
Cs2CO3
NaOAc
NaOAc
NaOAc
NaOAc
NaOAc
NaOAc
NaOAc
tBuOK
7
8
Pd/C
9
Pd/C
10
11
12b
13b
14b
15c
16
Pd/C
Pd/C
Pd/C
Pd/C
THF
n. r.
Pd/C
EtOH
DMA
DMA
n. r.
Pd/C
95 (1:0)
90 (0:1)
ꢀ
a Reaction conditions: 3ꢀIodoꢀ4ꢀphenoxybenzonitrile (3c) (100 mg), catalyst (5 mol%), base
b
c
(3 equiv.) in 3 mL of solvent, 140°C. Reaction was carried out at reflux temperature.
Reaction was carried out at in the presence of 0.3 mol% Pd/C for 16 h. n. r. represents no
reaction.
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Table 3. Pd/Cꢀcatalyzed synthesis of dibenzofuransa
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6
Entry
Substrate
Product
Yield (%)
7
O2N
8
9
100
1
2
3a
10
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12
13
14
15
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18
19
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O
OHC
NC
6a
90
3b
3c
O
6b
3
95
94
98
97
O
MeO2C
EtO2C
6c
4
5
3d
3e
O
6d
O
6e
PriO2C
6
7
3f
O
ButO2C
6f
3g
75
90
O
6g
MeOC
8
9
3h
O
O
6h
Ph
3i
N
84
82
Ph
O
6i
O
10
HN
Ph
3j
O
6j
Continued….
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4
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Entry
Substrate
Product
Yield (%)
CHO
90
11
3k
7
8
9
O
6k
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
12
90
3l
OHC
O
6l
CN
13
14
93
99
3m
3n
O
6m
NC
O
6n
COCH3
3o
3p
90
90
15
16
O
6o
H3COC
O
6p
O2N
Cl
95
93
3q
17
O
6q
O2N
Me
3r
18
O
6r
I
19
95
O
O
8
6s
a Reaction conditions: orthoꢀiododiaryl ether (50 mg), Pd/C (10 wt %) (3 mg, 0.3 mol %),
NaOAc (3 equiv.) in 3 mL of DMA at 140°C for 16 h.
With the optimized reaction conditions, we observed that all the synthesized orthoꢀ
iododiaryl ethers undergo cyclization smoothly to furnish the dibenzofurans in good to
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excellent yield. Functional groups such as ꢀNO2, ꢀCN, ꢀCHO, ꢀCOCH3, ꢀCONR2, ꢀCONHR, ꢀ
CO2R, etc. were found to be unaffected by the optimized reaction conditions (Table 3).
Furthermore, this protocol is also proficient to produce dibenzofurans (6s) from the orthoꢀ
iododiphenyl ethers (e.g. 8) in excellent yield without forming any hydrodehalogenated
product.
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It is noteworthy that the catalyst i.e. Pd/C used for the cyclization can be recovered
and may possess enough catalytic activity for the subsequent coupling reactions. The activity
of the used Pd/C was monitored by injecting 3ꢀiodoꢀ4ꢀphenoxybenzonitrile (5c) after the
completion of the reaction (after 16h) along with 3 equiv. of NaOAc (Table 4). We observed
that the rate of transformation becomes slightly sluggish, but catalytic efficiency is almost
unaltered even up to three consecutive cycles to produce 6c in 92% yield (from GC analysis).
It may be assumed that, the cyclization reaction proceed through the initial oxidative addition
leading to the intermediate I (Scheme 3). Subsequent insertion of an ortho aromatic CꢀH
bond to the Pd leads to the intermediate II. Reductive elimination from II finally affords the
dibenzofuran with the regeneration of Pd(0) for the subsequent catalytic cycle.
Table 4. Reusability of Pd/C for cyclization reaction
Cycle
Reaction time
% GC yield of 6c
1
2
3
16 h
24 h
24 h
95
92
92
Scheme 3. Plausible mechanism for the dibenzofuran synthesis
O
O
R
I
R
PdI
I
Pd0
O
O
R
R
Pd
I
H
II
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Conclusions
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In summary, a practical and efficient catalytic route for the intramolecular cyclization
of orthoꢀiodo diaryl ether to dibenzofuran using less expensive Pd (10 wt %) on charcoal
support was developed. We observed that 0.3 mol% of the catalyst was effective enough for
the arylꢀaryl bond formation through CꢀH activation, with excellent selectivity over
hydrodehalogenation reaction. Aryl iododiacetates were successfully used for oneꢀpot
sequential iodination and Oꢀarylation of phenol to furnish the orthoꢀiododiaryl ethers under
mild reaction conditions. This reaction can tolerate a wide variety of electronꢀwithdrawing
functional groups and is complementary to the previous methods for the synthesis of diaryl
ether with the tandem incorporation of additional iodoꢀfunctionality.
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Experimental Section
General procedure for the synthesis of ortho-iododiaryl ethers (3a-r)
A mixture of aryl alcohol 1 (100 mg), aryliodo diacetate (ArI(OAc)2) (1.5 equiv.), pivalic
acid (5 equiv.) in 3 mL of dichloroethane was stirred at 80°C. The progress of the reaction
was monitored by TLC. After 12 h, the reaction mixture was quenched with water (20 mL)
and then extracted with diethyl ether (3 × 15 mL). The combined organic layer was washed
with dilute ammonia (10%) solution (2 × 10 mL). Then, the solvent was removed under
reduced pressure, and the crude reaction mixture was purified by column chromatography
over silica gel (60ꢀ120 mesh) using mixture of ethyl acetate and petroleum ether as eluent.
General procedure for the Pd/C-catalyzed synthesis of dibenzofurans
To a mixture of orthoꢀiododiaryl ether (50 mg), NaOAc (3 equiv) in DMA (3 mL), 3 mg (0.3
mol %) of Pd/C (10 wt %)19 was added and the reaction mixture was heated at 140°C for 16
h. After completion of the reaction (monitored by GC), it was cooled to room temperature
and poured into water (10 mL). Then the product was extracted with ether (3 × 15 mL) and
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solvent was removed by rotary evaporator. The crude product was purified by column
chromatography over silica gel (60ꢀ120 mesh) using a mixture of ethyl acetate and petroleum
ether as eluent to afford the dibenzofuran 6 in 75ꢀ100% yield.
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2-Iodo-4-nitro-1-phenoxy-benzene (3a)
White low melting solid (240 mg, 98% yield); 1H NMR (400 MHz, CDCl3) δ 8.73 (d, 1H, J
= 2.8 Hz), 8.14ꢀ8.10 (m, 1H), 7.51ꢀ7.43 (m, 2H), 7.34−7.28 (m, 1H), 7.14ꢀ7.08 (m, 2H, ),
6.75 (d, 1H, J = 8.8 Hz); 13C NMR (100 MHz, CDCl3) δ 162.6, 154.6, 142.9, 135.4, 130.4,
125.8, 125.3, 120.4, 115.2, 86.0. HRMS (QꢀTOF ESI) m/z calcd for C12H9INO3 + [M + H]+
341.9627, found 341.9610.
3-Iodo-4-phenoxy-benzaldehyde 18a (3b)
1
Light yellow liquid (159 mg, 60% yield): H NMR (400 MHz, CDCl3) δ 9.86 (s, 1H), 8.38
(d, 1H, J = 2.0 Hz), 7.79ꢀ7.72 (m, 1H), 7.47ꢀ7.39 (m, 2H), 7.30ꢀ7.22 (m, 1H), 7.12ꢀ7.05 (m,
2H), 6.82 (d, 1H, J = 8.8 Hz); 13C NMR (100 MHz, CDCl3) δ 189.3, 162.1, 155.0, 141.6,
+
132.7, 131.3, 130.2, 125.3, 120.2, 116.5, 87.5. HRMS (QꢀTOF ESI) m/z calcd for C13H10IO2
[M + H]+ 324.9725, found 324.9728.
3-Iodo-4-phenoxy-benzonitrile (3c)
White solid (248 mg, 92% yield), m. p. 80°C; 1H NMR (400 MHz, CDCl3) δ 8.15 (d, 1H, J =
2 Hz) 7.57ꢀ7.50 (m, 1H), 7.49 ꢀ 7.41 (m, 2H), 7.31ꢀ7.24 (m, 2H), 7.08 (d, 2H, J = 7.6 Hz),
13
6.76 (d, 1H, J = 8.4 Hz) ; C NMR (100 MHz, CDCl3) δ 161.1, 154.7, 143.3, 133.6, 130.3,
125.4, 120.2, 117.1, 116.4, 107.8, 87.1; HRMS (QꢀTOF ESI) m/z calcd for C13H9INO+ [M +
H]+ 321.9729, found 321.9738.
3-Iodo-4-phenoxy-benzoic acid methyl ester18a (3d)
White solid (198 mg, 85% yield), m. p. 59°C; 1H NMR (400 MHz, CDCl3) δ 8.56 (d, 1H, J =
2 Hz) , 7.93 (dd, 1H, J1 = 8.4 Hz, J2 = 2 Hz), 7.46ꢀ7.38 (m, 2H), 7.27ꢀ7.19 (m, 1H), 7.07 (d,
2H, J = 7.6 Hz), 6.78 (d, 1H, J = 8.4 Hz) , 3.92 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 165.2,
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160.9, 155.4, 141.4, 137.4, 131.2, 130.2, 130.1, 126.2, 124.8, 119.8, 116.5, 86.9, 52.2;
+
HRMS (QꢀTOF ESI) m/z calcd for C14H12IO3 [M + H]+ 354.9831, found 354.9822.
7
8
3-Iodo-4-phenoxy-benzoic acid ethyl ester (3e)
9
Colourless liquid (177 mg, 80% yield); 1H NMR (400 MHz, CDCl3) δ 8.55 (d, 1H, J = 2 Hz),
7.93 (dd, 1H, J1 = 8.6 Hz, J2 = 2 Hz), 7.45ꢀ7.36 (m, 2H), 7.26ꢀ7.18 (m, 1H), 7.09ꢀ7.02 (m,
2H), 6.78 (d, 1H, J = 8.4 Hz), 4.38 (q, 2H, J = 7.2 Hz), 1.406 (t, 3H, J = 7.2 Hz); 13C NMR
(100 MHz, CDCl3) δ 164.7 (s), 160.7 (s), 155.5 (s), 141.3 (d), 131.2 (d), 130.1 (d), 126.6 (s),
124.7 (d), 119.7 (d), 116.6 (d), 87 (s), 61.2 (t), 14.3 (q); HRMS (QꢀTOF ESI) m/z calcd for
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60
+
C15H14IO3 [M + H]+ 368.9989, found 368.9981.
Isopropyl 3-iodo-4-phenoxybenzoate (3f)
1
Colourless liquid, (172 mg, 81% yield); H NMR (400 MHz, CDCl3) δ 8.54 (d, 1H, J = 2
Hz), 7.94 (dd, 1H, J1 = 8.4 Hz, J2 = 2 Hz), 7.41 (t, 2H, J = 7.8 Hz), 7.22 (t, 1H, J = 7.4 Hz),
7.05 (d, 2H, J = 8 Hz), 6.78 (d,1H, J = 8.8 Hz), 5.30ꢀ5.20 (m, 1H), 1.38 (d, 6H, J = 6.4 Hz).
13C NMR (100 MHz, CDCl3) δ 164.2, 160.6, 155.6, 141.3, 131.2, 130.1, 127.1, 124.7, 119.6,
+
116.7, 87.0, 68.7, 21.6; HRMS (QꢀTOF ESI) m/z calcd for C16H16IO3 [M + H]+ 383.0144,
found 383.0133.
Tert-butyl 3-iodo-4-phenoxybenzoate (3g)
1
Colourless liquid (143 mg, 70% yield); H NMR (400 MHz, CDCl3) δ 8.49 (d, 1H, J = 2
Hz), 7.90 (dd, 1H, J1 = 8.6 Hz, J2 = 1.8 Hz), 7.40 (t, 2H, J = 8.4 Hz), 7.21 (t, 1H, J = 7.6 Hz),
7.05 (d, 2H, J = 8 Hz), 6.78 (d, 1H, J = 8.8 Hz), 1.60 (s, 9H). 13C NMR (100 MHz, CDCl3)
δ 163.9, 160.3, 155.7, 141.2, 131.1, 130.1, 128.3, 124.6, 119.6, 116.7, 87.0, 81.5, 28.2;
+
HRMS (QꢀTOF ESI) m/z calcd for C13H10IO3 [M+2H ꢀ tBu]+ 340.9675, found 340.9677.
1-(3-Iodo-4-phenoxy-phenyl)-ethanone (3h)
1
Colourless liquid (176 mg, 71% yield); H NMR (400 MHz, CDCl3) δ 8.47 (d, 1H, J = 1.6
Hz) , 7.85 (d, 1H, J = 8.8 Hz), 7.46ꢀ7.38 (m, 2H ), 7.27ꢀ7.19 (m, 1H), 7.07 (d, 2H, J = 8 Hz ),
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6.78 (d, 1H, J = 8.4 Hz), 2.57 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 195.5, 161.0, 155.3,
5
6
140.5,133.5, 130.1, 130.0, 124.9, 119.9, 116.5, 87.3, 26.4; GC MS (EI, +ve) m/z (relative
7
8
+
intensity) 337.9 ([M]+, 100%). HRMS (QꢀTOF ESI) m/z calcd for C14H12IO2 [M+H]+
9
338.9882, found 338.9889.
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3-Iodo-4-phenoxy-N, N-diphenylbenzamide (3i)
1
White yellowish solid (109 mg, 64% yield); m. p. 138°C; H NMR (400 MHz, CDCl3) δ
8.01 (d, 1H, J = 2 Hz), 7.41ꢀ7.29 (m, 7H), 7.23 (t, 2H, J = 7.4 Hz), 7.20ꢀ7.11 (m, 5H), 6.96
(d, 2H, J = 8 Hz), 6.60 (d, 1H, J = 8.4 Hz); 13C NMR (100 MHz, CDCl3) δ 168.3, 158.3,
155.7, 143.6, 141.2, 137.4, 132.2, 130.8, 130.2, 130.0, 129.2, 127.4, 127.4, 126.6, 124.4,
119.3, 116.7, 87.0; HRMS (QꢀTOF ESI) m/z calcd for C25H19INO2 [M+H]+ 492.0462, found
+
492.0455.
3-Iodo-4-phenoxy-N-phenyl-benzamide (3j)
1
Yellowish solid (119 mg, 61% yield), m. p. 145°C; H NMR (400 MHz, CDCl3) δ 8.39ꢀ8.33
(m,1H), 8.35 (s, 1H), 7.78 (dd, 1H, J1 = 8.8 Hz, J2 = 2.4 Hz), 7.64 (d, 2H, J = 8 Hz), 7.46ꢀ7.34
(m, 4H), 7.25 (s, 1H), 7.25ꢀ7.14 (m, 1H), 7.06 (d, 2H, J = 8 Hz) 6.83 (d, 1H, J = 8.8 Hz); 13C
NMR (100 MHz, CDCl3) δ 163.7, 159.9, 155.6, 138.7, 137.6, 131.1, 130.1, 129.1, 128.8,
+
124.8, 124.7, 120.3, 119.6, 117.2, 87.7; HRMS (QꢀTOF ESI) m/z calcd for C19H15INO2 [M
+ H]+ 416.0147, found 416.0129.
2-Iodo-3-phenoxy-benzaldehyde (3k)
Light yellow liquid; 1H NMR (400 MHz, CDCl3) δ 10.23 (d,1H, J = 0.8 Hz), 7.67 (dd, 1H, J1
= 7.6 Hz, J2 = 1.6 Hz), 7.44ꢀ7.34 (m, 3H), 7.21 (d, 1H, J = 0.8 Hz), 7.19ꢀ7.09 (m, 1H), 7.05ꢀ
6.99 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 195.9, 157.2, 156.5, 137.1, 130.0, 129.6, 125.2,
124.2, 124.1, 118.6, 115.3, 96.0; GC MS (EI, +ve) m/z (relative intensity) 323.9 ([M]+,
100%). HRMS (QꢀTOF ESI) m/z calcd for C13H10IO2 [M + H]+ 324.9725, found 324.9712.
+
4-iodo-3-phenoxybenzaldehyde (3l)
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Pale yellow solid, m. p. 60°C; 1H NMR (400 MHz, CDCl3) δ 9.88 (s, 1H), 8.09 (d, 1H, J = 8
Hz), 7.72 (dd, 1H, J1 = 8.4 Hz, J2 = 1 Hz), 7.46ꢀ7.38 (m, 2H), 7.38ꢀ7.31 (m, 1H), 7.26ꢀ7.13
(m, 1H), 7.08ꢀ7.02 (m, 2H). 13C NMR (100 MHz, CDCl3) δ 190.8, 140.7, 137.8, 137.4,
130.2, 130.1, 127.4, 125.6, 124.6, 119.2, 117.2, 96.9; GC MS (EI, +ve) m/z (relative
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+
intensity) 323.9 ([M]+, 100%). HRMS (QꢀTOF ESI) m/z calcd for C13H10IO2 [M + H]+
324.9725, found 324.9729.
2-Iodo-3-phenoxybenzonitrile (3m)
1
White solid, m. p. 110°C; H NMR (400 MHz, CDCl3) δ 7.45ꢀ7.35 (m, 4H), 7.22 (t, 1H, J =
7.4 Hz), 7.05ꢀ6.97 (m, 3H); 13C NMR (100 MHz, CDCl3) δ 158.3, 155.6, 130.2, 130.0, 129.0,
124.7, 122.6, 121.7, 119.2, 119.1, 93.1; GC MS (EI, +ve) m/z (relative intensity) 296.9 ([M +
H]+, 100%); GC MS (EI, +ve) m/z (relative intensity) 320.9 ([M]+, 99%), 193.9 ([M+HꢀI]+,
100%). HRMS (QꢀTOF ESI) m/z calcd for C13H9INO+ [M + H]+ 321.9729, found 321.9721.
4-Iodo-3-phenoxybenzonitrile (3n)
Colourless liquid; 1H NMR (400 MHz, CDCl3) δ 7.99 (d, 1H, J = 8 Hz), 7.48ꢀ7.26 (m, 2H),
7.26 (t, 1H, J = 7.2 Hz), 7.10 (dd, 1H, J1 = 8.2 Hz, J2 = 2 Hz), 7.08ꢀ7.01 (m, 2H), 6.98 (d,
1H, J = 2 Hz); 13C NMR (100 MHz, CDCl3) δ 157.8, 155.1, 140.9, 130.3, 127.3, 125.1,
119.9, 119.6, 117.7, 113.2, 94.5; GC MS (EI, +ve) m/z (relative intensity) 320.9 ([M]+, 99%),
193.9 ([M+HꢀI]+, 100%). HRMS (QꢀTOF ESI) m/z calcd for C13H9INO+ [M + H]+ 321.9729,
found 321.9734.
1-(2-Iodo-3-phenoxy-phenyl)-ethanone (3o) / 1-(4-iodo-3-phenoxyphenyl)ethanone (3p)
1
Inseparable mixture (136 mg, 40% yield); H NMR (400 MHz, CDCl3) δ 7.99 (d,1H, J = 8.4
Hz), 7.46ꢀ7.29 (m, 9H ), 7.21ꢀ6.99 (m, 9H), 6.92 (dd, 2H, J1 = 8.4 Hz, J2 = 1.2Hz); 13C NMR
(100 MHz, CDCl3) δ 202.7, 196.7, 157.2, 157.1, 156.5, 156.2, 147.9, 140.2, 138.7, 130.1,
130.0, 129.7, 124.6, 124.1, 123.9, 122.4, 120.2, 118.7, 118.6, 117.7, 95.7, 85.9, 30.0, 26.6.
1-(2-iodo-4-nitrophenoxy)-4-chlorobenzene (3q)
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White solid (82 mg, 61% yield), m. p. 100ꢀ102 °C ; H NMR (400 MHz, CDCl3) δ 8.76 (d,
5
6
7
8
1H, J = 2.4 Hz), 8.15 (dd, 1H, J1 = 7.6 Hz, J2 = 2.8 Hz), 7.43 (d, 2H, J = 8.8 Hz), 7.05 (d, 2H,
J = 8.8 Hz), 6.77 (d, 1H, J = 8.8 Hz); 13C NMR (100 MHz, CDCl3) δ 162.1, 153.3, 143.3,
135.6, 131.0, 130.4, 125.3, 121.5, 115.5, 86.2. HRMS (QꢀTOF ESI) m/z calcd for
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+
C12H8ClINO3 [M + H]+ 375.9237, found 375.9231.
1-(2-iodo-4-nitrophenoxy)-4-methylbenzene (3r)
1
Off white gummy solid (76 mg, 60% yield); H NMR (400 MHz, CDCl3) δ 8.75 (d, 1H, J =
2.8 Hz), 8.18 (dd, 1H, J1 = 7.6 Hz, J2 = 2.8 Hz), 7.26 (d, 2H, J = 8.0 Hz), 6.95 (d, 2H, J = 8.4
Hz), 6.72 (d, 1H, J = 7.6 Hz), 2.40 (s,1H); 13C NMR (100 MHz, CDCl3) δ 159.7, 153.2,
145.2, 135.3, 132.7, 130.8, 130.4, 120.3, 115.3, 90.6, 20.6. HRMS (QꢀTOF ESI) m/z calcd
for C13H11INO3 [M + H]+ 355.9784, found 355.9776.
+
1-Iodo-2-phenoxybenzene20 (8)
Colourless liquid, 1H NMR (400 MHz, CDCl3) δ 7.93 (dd, 1H , J1 = 8 Hz, J2 = 1.6 Hz),7.45ꢀ
7.34 (m, 2H), 7.36ꢀ7.30 (m, 1H), 7.23ꢀ7.15 (m, 1H), 7.09ꢀ7.02 (m, 2H), 7.00ꢀ6.89 (m, 2H);
13C NMR (100 MHz, CDCl3) δ 156.9, 156.5, 139.9, 128.9, 129.8, 125.4, 123.6, 119.5, 118.5;
GC MS (EI, +ve) m/z (relative intensity) 296.9 ([M + H]+, 100%).
2-Nitro-dibenzofuran21 (6a)
1
White solid (31 mg, 100% yield), m. p. 151ꢀ152°C; H NMR (400 MHz, CDCl3) δ 8.90 (d,
1H, J = 1.6 Hz), 8.46ꢀ8.39 (m, 1H), 8.06 (d, 2H, J1 = 8.4 Hz), 7.71−7.67 (m, 2H), 7.64ꢀ7.56
(m, 1H), 7.51ꢀ7.43 (m, 1H); 13C NMR (100 MHz, CDCl3) δ 159.2, 157.4, 143.8, 128.9,
125.0, 123.9, 123.1, 123.0, 121.3, 117.1, 112.2, 112.0; HRMS (QꢀTOF ESI) m/z calcd for
+
C12H7NNaO3 [M + Na]+ 236.0324, found 236.0307.
Dibenzofuran-2-carbaldehyde22 (6b)
White crystalline solid (27 mg, 90% yield), m. p. 70°C; 1H NMR (400 MHz, CDCl3) δ 10.12
(s, 1H) 8.47 (s, 1H), 8.01 (d, 2H, J = 8.0 Hz), 7.70ꢀ7.65 (m, 1H), 7.63ꢀ7.58 (m, 1H), 7.57ꢀ
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7.51 (m, 1H), 7.46ꢀ7.40 (m, 1H); C NMR (100 MHz, CDCl3) δ 191.4, 159.7, 156.8, 131.9,
5
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129.2, 128.2, 125.1, 123.6, 123.3, 123.0, 121.1, 112.3, 112.0; HRMS (QꢀTOF ESI) m/z calcd
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8
+
for C13H9O2 [M + H]+ 197.0603, found 197.0597.
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Dibenzofuran-2-carbonitrile22 (6c)
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White solid (28 mg, 95% yield), m. p.136°C; H NMR (400 MHz, CDCl3) δ 8.25 (s,1H)
7.97 (d, 1H, J = 8 Hz), 7.77ꢀ7.71 (m, 1H), 7.67ꢀ7.59 (m, 2H), 7.60ꢀ7.52 (m, 1H, ), 7.43 (t,
1H, J = 7.6 Hz); 13C NMR (100 MHz, CDCl3) δ 157.9, 156.7, 130.8, 128.7, 125.4, 125.2,
123.7, 122.5, 121.1, 119.2, 112.8, 112.1, 106.5; HRMS (QꢀTOF ESI) m/z calcd for
C13H8NO+ [M + H]+ 194.0606, found 194.0597.
Dibenzofuran-2-carboxylic acid methyl ester15b (6d)
White solid (30 mg, 94% yield), m. p. 76°C; 1H NMR (400 MHz, CDCl3) δ 8.70 (d, 1H, J =
1.6 Hz), 8.20 (dd, 1H, J1 = 8.4 Hz, J2 = 1.6 Hz), 8.05ꢀ7.99 (m, 1H), 7.64ꢀ7.58 (m, 2H), 7.56ꢀ
7.48 (m, 1H ),7.45ꢀ7.37 (m, 1H), 4.00 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 167.0, 158.8,
156.7, 128.9, 127.8, 124.9, 124.4, 123.7, 123.3, 122.9, 120.9, 111.9, 111.5, 52.2; HRMS (Qꢀ
TOF ESI) m/z calcd for C14H11O3 [M + H]+ 227.0708, found 227.0698.
+
Dibenzofuran-2-carboxylic acid ethyl ester23 (6e)
1
White solid (32 mg, 98% yield), m. p. 58°C; H NMR (400 MHz, CDCl3) δ 8.67 (d,1H, J =
1.2 Hz) , 8.23ꢀ8.17 (m, 1H), 8.00 (d, 1H, J =7.6 Hz), 7.63ꢀ7.55 (m, 2H), 7.54ꢀ7.46 (m, 1H ),
7.43ꢀ7.35 (m, 1H), 4.46 (q, 2H, J = 7.2 Hz), 1.47 (t, 3H, J = 7.2 Hz); 13C NMR (100 MHz,
CDCl3) δ 166.5, 158.8, 156.7, 128.9, 127.8, 125.3, 124.3, 123.7, 123.2, 122.8, 120.9, 111.8,
111.4, 61.1, 14.4; HRMS (QꢀTOF ESI) m/z calcd for C15H13O3 [M + H]+ 241.0865, found
+
241.0859.
Dibenzofuran-2-carboxylic acid isopropyl ester (6f)
1
White solid (32 mg, 97% yield), m. p. 68 °C; H NMR (400 MHz, CDCl3) δ 8.68 (s, 1H),
8.20 (dd, 1H, J1 = 8.4 Hz, J2 = 1.2 Hz) 8.02 (d, 1H, J = 7.6 Hz), 7.64ꢀ7.56 (m, 2H), 7.51 (t,
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1H, J = 7.8 Hz), 7.40 (t, 1H, J = 7.4 Hz), 5.39ꢀ5.29 (m, 1H), 1.45 (d, 6H, J = 6 Hz); 13C
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6
NMR (100 MHz, CDCl3) δ 166.0, 158.7, 156.7, 128.9, 127.8, 125.7, 124.3, 123.7, 123.2,
7
8
+
122.8, 121.0, 111.8, 111.3, 68.5, 22.0; HRMS (QꢀTOF ESI) m/z calcd for C16H15O3 [M +
9
H]+ 255.1021, found 255.1014.
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Tert-butyl dibenzofuran-2-carboxylate (6g)
1
Colourless liquid (25 mg, 75% yield); H NMR (400 MHz, CDCl3) δ 8.63 (d, 1H, J = 1.2
Hz), 8.16 (dd, 1H, J1 = 8.8 Hz, J2 = 1.6 Hz), 8.02 (d, 1H, J = 7.6 Hz), 7.60 (t, 2H, J = 8.8 Hz),
7.51 (t, 1H, J = 7.8 Hz), 7.40 (t, 1H, J = 7.6 Hz), 1.67 (s, 9H). 13C NMR (100 MHz, CDCl3)
δ 165.5, 158.6, 156.7, 128.8, 127.7, 126.8, 124.2, 123.8, 123.2, 122.6, 120.9, 111.8, 111.2,
81.1, 28.3; HRMS (QꢀTOF ESI) m/z calcd for C13H9O3 [M + 2H ꢀ Bu]+ 213.0552, found
+
t
213.0542.
2-Acetyldibenzofuran4e (6h)
White solid (28 mg, 90% yield), m. p. 203°C; 1H NMR (400 MHz, CDCl3) δ 8.61 (d, 1H, J
= 2 Hz), 8.13 (dd, 1H, J1 = 8.8 Hz, J2 = 2 Hz), 8.02 (d, 1H, J = 7.6 Hz), 7.62 (d, 2H, J = 8.4
Hz), 7.57ꢀ7.49 (m, 1H),7.45ꢀ7.38 (m, 1H), 2.74 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 197.3
(s), 158.9 (s), 156.8 (s), 132.5 (s), 128.0 (d), 124.5 (s), 123.7 (s), 123.4 (d), 121.6 (d), 120.9
(d), 111.9 (d), 111.6 (d), 26.8 (s); HRMS (QꢀTOF ESI) m/z calcd for C14H11O2 [M + H]+
+
211.0759, found 211.0751.
N,N-diphenyldibenzofuran-2-carboxamide (6i)
White solid (31 mg, 84% yield), m. p. 128°C; 1H NMR (400 MHz, CDCl3) δ 8.21(d, 1H, J =
2 Hz), 7.89 (d, 1H, J = 8 Hz) 7.60ꢀ7.53 (m, 2H),7.52ꢀ7.44 (m, 1H) 7.40ꢀ7.26 (m, 6H), 7.25ꢀ
7.17 (m, 6H).13C NMR (100 MHz, CDCl3) δ 170.6, 156.9, 156.6, 144.1, 130.8, 129.2, 128.6,
127.6, 127.5, 126.4, 124.0, 123.7, 123.1, 122.6, 120.8, 111.8, 110.9; HRMS (QꢀTOF ESI)
+
m/z calcd for C25H18 NO2 [M + H]+ 364.1338, found 364.1333.
Dibenzofuran-2-carboxylic acid phenylamide (6j)
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White solid (28 mg, 82% yield), m. p. 180 °C; 1H NMR (400 MHz, CDCl3) δ 8.46 (d,1H, J =
1.6Hz), 8.17 (s, 1H), 7.98ꢀ7.91 (m, 2H), 7.72 (d, 2H, J = 7.6 Hz), 7.63ꢀ7.55 (m, 2H),7.56ꢀ
7.47 (s, 1H), 7.44ꢀ7.34 (m, 3H),7.22ꢀ7.15(m, 1H); 13C NMR (100 MHz, CDCl3) δ 165.8,
158.0, 156.8, 138.0, 129.8, 129.1, 128.0, 126.1, 124.7, 124.6, 123.5, 123.3, 120.9, 120.3,
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120.3, 111.9, 111.7; HRMS (QꢀTOF ESI) m/z calcd for C19H14NO2 [M + H]+, 288.1025,
found 288.1030.
Dibenzofuran-1-carbaldehyde24 (6k)
1
White solid (27 mg, 90% yield), m. p. 64°C; H NMR (400 MHz, CDCl3) δ 10.39 (s,1H) ,
8.96 (d, 1H, J = 7.6 Hz ), 7.86 (t, 2H, J = 8 Hz), 7.68ꢀ7.55 (m, 3H) ,7.48ꢀ7.40 (m, 1H); 13C
NMR (100 MHz, CDCl3) δ 192.2, 157.0, 156.6, 132.0, 129.5, 128.9, 126.6, 126.4, 123.1,
123.1, 122.9, 117.4, 111.4; HRMS (QꢀTOF ESI) m/z calcd for C13H9O2 [M + H]+, 197.0603
+
found 197.0609.
3-Dibenzofurancarboxaldehyde (6l)
1
White solid, (27 mg, 90% yield), m. p. 130°C; H NMR (400 MHz, CDCl3) δ 10.12 (s, 1H),
8.08 (d, 2H, J = 8 Hz) 8.02 (d, 1H, J = 8 Hz), 7.89 (dd, 1H, J1 = 8 Hz, J2 = 1.2 Hz), 7.63 (d,
1H, J = 8.4 Hz), 7.61ꢀ7.53 (m, 1H), 7.45ꢀ7.37 (m, 1H). 13C NMR (100 MHz, CDCl3) δ
191.6, 157.7, 155.9, 135.3, 130.0, 129.0, 124.7, 123.3, 123.1, 121.6, 121.0, 112.6, 112.1;
HRMS (QꢀTOF ESI) m/z calcd for C13H9O2 [M + H]+, 197.0603 found 197.0610.
+
1-Dibenzofurancarbonitrile25 (6m)
White solid (28 mg, 93% yield), m. p. 104°C; 1H NMR (400 MHz, CDCl3) δ 8.40 (d, 1H, J =
8 Hz), 7.80 (d, 1H, J = 8.4 Hz) 7.69ꢀ7.58 (m, 3H), 7.53 (t, 1H, J = 8 Hz) 7.47ꢀ7.43 (m, 1H);
13C NMR (100 MHz, CDCl3) δ 156.6, 155.6, 129.1, 127.2, 126.9, 125.8, 123.6, 121.9, 121.7,
117.4, 116.3, 111.9, 104.4; HRMS (QꢀTOF ESI) m/z calcd for C13H8NO+ [M + H]+,
194.0606 found 194.0601.
3-Cyanodibenzofuran26 (6n)
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White solid (30 mg, 99% yield), m. p. 124 °C; H NMR (400 MHz, CDCl3) δ 8.07ꢀ7.99 (m,
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6
7
8
2H), 7.66 (s, 1H) 7.65 (dd, 2H, J1 = 8.2 Hz, J2 = 1 Hz), 7.63ꢀ7.55 (m, 1H), 7.48ꢀ7.40 (m, 1H);
13C NMR (100 MHz, CDCl3) δ 157.2, 154.9, 129.3, 128.6, 126.6, 123.6, 122.7, 121.5, 121.4,
119.1, 115.7, 112.1, 109.7; HRMS (QꢀTOF ESI) m/z calcd for C13H8NO+ [M + H]+,
194.0606 found 194.0599.
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1-Acetyl dibenzofuran (6o)
Colourless liquid (28 mg, 90% yield); 1H NMR (400 MHz, CDCl3) δ 8.83 (d,1H, J = 8.4Hz) ,
7.88 (d, 1H, J = 7.6 Hz) 7.81 (d, 1H, J = 8 Hz), 7.64ꢀ7.51 (m, 3H), 7.44ꢀ7.36 (m, 1H), 2.82 (s,
3H); 13C NMR (100 MHz, CDCl3) δ 197.4, 157.6, 155.9, 136.0, 128.7, 128.6, 123.3, 123.2,
+
123.1, 121.4, 120.4, 112.0, 111.8, 26.9; HRMS (QꢀTOF ESI) m/z calcd for C14H11O2 [M +
H]+, 211.0759 found 211.0753.
3-Acetyl dibenzofuran27 (6p)
1
White solid (28 mg, 90% yield), m. p. 121°C; H NMR (400 MHz, CDCl3) δ 8.19 (s, 1H),
8.07ꢀ7.97 (m, 3H) 7.64 (d, 1H, J = 8.4 Hz), 7.60ꢀ7.52(m, 1H), 7.45ꢀ7.41 (m, 1H), 2.73 (s,
3H); 13C NMR (100 MHz, CDCl3) δ 199.5, 157.0, 156.8, 133.6, 128.4, 126.4, 126.2, 125.1,
+
123.1, 122.9, 122.8, 116.1, 111.2, 28.6; HRMS (QꢀTOF ESI) m/z calcd for C14H11O2 [M +
H]+, 211.0759 found 211.0751.
8-Chloro-2-nitrodibenzofuran (6q)
1
White Crystalline solid (31 mg, 95%), m. p. 224°C; H NMR (400 MHz, CDCl3): δ 8.84 (d,
1H, J = 2.4 Hz), 8.44 (dd, 1H, J1 = 7.6 Hz, J2 = 2.4 Hz), 8.01 (d, 1H, J = 2.4 Hz), 7.68 (d,
1H, J = 8.8 Hz), 7.61ꢀ7.50 (m, 2H); 13C NMR (100 MHz, CDCl3): δ 159.6, 155.7, 144.0,
129.6, 129.0, 124.4, 124.0, 123.6, 121.1, 117.3, 113.3, 112.3. HRMS (QꢀTOF ESI) m/z calcd
+
for C12H7ClNO3 [M + H]+, 248.0114 found 248.0108.
8-Methyl-2-nitrodibenzofuran4f(6r)
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White solid (30 mg, 93% yield), m. p. 146°C; H NMR (400 MHz, CDCl3): δ 8.82 (s, 1H),
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6
7
8
8.37 (d, 1H, J = 8.8 Hz), 7.81 (s, 1H), 7.62 (d, 1H, J = 8.8 Hz), 7.52 (d, 1H, J = 8.4 Hz),
7.38 (d, 1H, J = 8.4 Hz), 2.55 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 159.4, 155.82, 143.7,
133.6, 130.0, 124.9, 123.0, 122.7, 121.1, 116.9, 111.8, 111.7, 21.3.
Dibenzofuran15b (6s)
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White solid (27 mg, 95% yield), m. p. 83 °C; 1H NMR (400 MHz, CDCl3) δ 7.99 (d, 2H, J =
4.6 Hz), 7.61 (d, 2H, J = 8.4 Hz),7.53ꢀ7.45 (m, 2H),7.42ꢀ7.55 (m, 1H) 7.48ꢀ7.34 (m, 2H); 13C
NMR (100 MHz, CDCl3) δ 156.1, 127.1, 124.2, 122.7, 120.6, 118.4, 111.6; GC MS (EI, +ve)
m/z (relative intensity) 167.9 ([M]+, 100%).
Supporting Information
NMR spectra of compounds 3a-r, 8 and 6a-s. This material is available free of charge via the
Internet at http://pubs.acs.org.
Acknowledgements
This work was financially supported by SERB, (No. SB/S1/OCꢀ21/2014), DST, Government
of India.
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