Rapid Access to Bi- and Tri-Functionalized Dibenzofurans and their Application in Selective Suzuki–Miyaura Cross Coupling Reactions

Article abstract of DOI:10.1002/ejoc.201801286

Syntheses of 1,2-, 1,3-, 1,4-, 1,8-, 2,4-, 3,4-, 4,8-, 1,2,4-, 1,2,8- and 1,3,4-functionalized dibenzofurans in few steps with good to excellent yields starting from dibenzofuran-1-ol or -4-ol are presented. These rapidly accessible bi- or tri-functionalized building blocks are of great interest for the synthesis of bioactive substances or functional material development. Furthermore, for intermediates containing both a bromine and a triflate moiety, a selective mono-substitution by means of Suzuki–Miyaura reaction (SMR) is described.

Full text of DOI:10.1002/ejoc.201801286

A Journal of
Accepted Article
Title: Rapid Access to bi- and tri-functionalized Dibenzofurans and
their Application in selective Suzuki-Miyaura Cross Coupling
Reactions
Authors: Caroline Wern, Christian Ehrenreich, Dominik Joosten,
Thorsten Vom Stein, Herwig Buchholz, and Burkhard König
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To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201801286
Link to VoR: http://dx.doi.org/10.1002/ejoc.201801286
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10.1002/ejoc.201801286
European Journal of Organic Chemistry
FULL PAPER
Rapid Access to bi- and tri-functionalized Dibenzofurans and
their Application in selective Suzuki-Miyaura Cross Coupling
Reactions
Caroline Wern,[a,b] Christian Ehrenreich,[b] Dominik Joosten,[b] Thorsten vom Stein,[b] Herwig Buchholz,[b]
Burkhard König*[a]
purified material.[8] Tri-functionalized dibenzofurans are
Abstract: Syntheses of 1,2-, 1,3-, 1,4-, 1,8-, 2,4-, 3,4-, 4,8-, 1,2,4-,
1,2,8- and 1,3,4-functionalized dibenzofurans in few steps with good
occasionally reported, but only in patent literature.[10]
to excellent yields starting from dibenzofuran-1-ol or -4-ol are
presented. These rapidly accessible bi- or tri-functionalized building
blocks are of great interest for the synthesis of bioactive substances
or functional material development. Furthermore, for intermediates
containing both a bromine and a triflate moiety, a selective mono-
substitution by means of Suzuki-Miyaura reaction (SMR) is
described.
1-Aminodibenzofuran is a typical starting material, which is, after
conversion of the amine into an alcohol via “Phenolverkochung”,
subjected to Suzuki C-C cross coupling reactions. The synthetic
route is prolonged by the additional transformations and thus the
overall yield decreases.
Triflate-Suzuki reactions were introduced in the 1990s by
Suzuki,[11] Huth[12] and Snieckus.[13] Triflates are known to be
less reactive than bromides and iodides in Suzuki reactions.[14]
Functional group selective cross coupling reactions in molecules
bearing triflate and bromine as leaving groups by means of
Suzuki reaction are challenging.[14, 15] For Kumada, Negishi and
Introduction
Dibenzofuran motifs are found in natural products,[1] in synthetic
molecules with biological activity[2] or in imaging tools.[3] The
dibenzofuran core structure is attractive for material research,
e.g. for light-emitting devices, due to its defined and rigid
geometry.[4] There are various ways to prepare substituted
dibenzofurans. In general, two approaches are possible: a)
Stille coupling, bulky monophosphine ligands allow for
a
preferred insertion into the C-Br bond, while chelating
aryldiphosphine ligands such as 1,3-bis(diphenylphosphino)-
propane (dppp) switch the selectivity to preferred insertion into
the C-OTf bond.[15, 16] For Suzuki coupling, both types of ligands
are reported to address the C-Br bond.[15, 17] Bromine selective
Suzuki couplings of 1,3- or 1,4-bromo aryl triflates are reported
using tri-tert-butylphosphine (PtBu3) or triphenylphosphine
(PPh3) as ligand.[11, 15, 18] The combination of Pd(OAc)2 and tri-
ortho-tolylphosphine (P(o-Tol)3) is reported to favor bromine over
triflate coupling to some extent in terms of Suzuki-mediated
vinylation of naphthalene derivatives.[19] However, steric or
electronic effects of ortho-substituents are reported to foster the
triflate over bromine transformation using common catalysts
such as tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4).
Sterical effects can occur due to catalyst-directing effects, e.g. of
carbonyl groups.[20] In terms of bis(triflates) and halogenated
heterocycles, site-selective Suzuki couplings are reported to
occur first on sterically less hindered and electronically more
deficient positions.[21] The triflate selective coupling of bromo aryl
triflates with alkyl Grignard reagents is also reported. However,
Sonogashira coupling of those bromo aryl triflates afforded the
bromine-converted coupling product.[22]
Herein, we report short, highly selective and high yielding routes
to bi- and tri-functionalized dibenzofuran intermediates for
further derivatization starting from dibenzofuran-1-ol or -4-ol.
These starting materials are commercially available[23] or e.g.
accessible through condensation reactions[24] or by oxidation of
the corresponding boronic acids.[25] The use of dibenzofuranols
allows for a broad variety of core derivatizations by modification
of the hydroxyl moiety and thus selectivity of functionalizations.
Moreover, we report the bromine or triflate-selective mono-
substitution of bromo aryl triflates by means of Suzuki-Miyaura
reaction (SMR), respectively.
Formation
of
a
substituted
dibenzofuran
core
b) Functionalization of an existing dibenzofuran motif. The first
approach allows for a broad spectrum of possible substitution
patterns. However, multi-step reactions are typically required to
synthesize the dibenzofuran ring system.[4b, 5] Thus,
regioselectivity and purification challenges occur frequently as
isomers are obtained during ring closure reaction.[4b, 6] The
second approach circumvents the need for a regioselective ring
closure. However, highly chemoselective reactions are required
for such late stage functionalizations.
In the 1930s to 1950s, Gilman and co-workers described various
substitution patterns and trends in reactivity and selectivity for
functionalization of
dibenzofuran motifs. In general,
4-, 6- or 4,6-substituted dibenzofurans are accessible via
metalation of dibenzofuran followed by reaction with an
electrophile.[7] Halogenation and sulfonation are reported to
address the 2-position, while nitration allows for functionalization
of the 3-position.[7c] However, in most cases the reported yields
of purified products are below 40 %,[8] limiting the use in
preparative organic chemistry. Moreover, double halogenation
occurred frequently for some derivatives, showing a lack of
regioselectivity.[9] This drawback was also reported for the
synthesis of 1-bromo-dibenzofuran-2-ol more recently.[2a]
Furthermore, the exact substitution pattern of the brominated
product of dibenzofuran-1-ol remained unclear due to lack of
[a]
[b]
Caroline Wern, Prof. Dr. Burkhard König,
Faculty of Chemistry and Pharmacy, University of Regensburg,
Caroline Wern, Dr. Christian Ehrenreich, Dr. Dominik Joosten,
Dr. Thorsten vom Stein, Prof. Dr. Herwig Buchholz,
Merck KGaA, Performance Materials Division,
Frankfurter Straße 250, 64293 Darmstadt
Results and Discussion
Triflate formation of dibenzofuran-1-ol (1) and subsequent
bromination of 2 using NBS, trifluoromethansulfonic acid (TfOH)
in dichloromethane (DCM) at room temperature allowed for the
synthesis of the 1,8-substitution pattern in 5 (Scheme 1). A
selective borylation of the bromine moiety to give 10 was
Supporting Information for this article is given via a link at the end of
the document.
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Scheme 1. Bi- or tri-functionalized building blocks derived from dibenzofuran-1-ol. R1 = Phenyl, R2 = 9-Phenyl-carbazole-3-yl.
possible using bis(pinacolato)diboron (B2pin2), Pd(dppf)Cl2 and
KOAc in toluene at 80 °C. A similar reaction using the same
catalytic system was reported previously, but details on solvent,
base and temperature were not given.[26] Treatment of 1 with
NBS in DCM yielded 1,2-substituted 3. Subsequent SMR of 3
with phenylboronic acid, triflate formation and bromination gave
access to a 1,2,8-substitution pattern in 7. The bromine-selective
borylation of 7 to 11 was also possible in excellent yield. Since
material at room temperature. However, the addition of catalytic
amounts of HCl resulted in a product mixture (Table 1).
Table 1. HCl catalyzed chlorination of 2-bromo-dibenzofuran-1-ol.
the direct bromination of dibenzofuran-1-ol (1) led to
1,2-pattern with excellent selectivity, a derivatization of the
phenol function was required to get access to 1,4-
a
a
Ratio determined by GC-MS [%]
functionalization. Masking the phenol function with a bulky
triisopropylsilane (TIPS) group disfavored hydroxyl-mediated
bromination in the ortho position as a result of steric shielding,
but did not alter the electronic properties too much and hence
directing effects of the hydroxyl group were still operative. As a
result, bromination of 4 and removal of the TIPS group using
CsF in a one-pot procedure gave access to 8 with excellent
regioselectivity.[27] Chlorination of 3 with N-chlorosuccinimid
(NCS) in THF failed to give any conversion of the starting
Entry
Temp. [°C]
3
15
16
17
11.2
8.1
1
2
3
23
0
8.7
6.0
6.9
58.3
73.7
79.6
17.4
12.2
7.4
-20
6.0
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In a temperature range of +23 to -20 °C, an acid-catalyzed
rearrangement took place,[28] so that the desired compound 15
was accompanied by doubly brominated, doubly chlorinated
species and starting material. Even though the ratio of these four
species was affected by the reaction temperature, this strategy
was abandoned as the prospect of achieving a clean conversion
to the target molecule at even lower reaction temperatures was
supposed to be low. In contrast, HCl catalyzed chlorination of
1,4-substituted 8 with NCS in THF allowed the isolation of the
1,2,4-substituted dibenzofuran 12 in 95 % yield (Scheme 1). In
the absence of catalytic amounts of HCl, no reaction occurred.
The conversion of the (halogenated) dibenzofuranol species
provided the corresponding triflates 6, 9 and 13 in yields of
76 - 95 % using standard reaction conditions (Tf2O, NEt3, DCM).
Hydrodeoxygenation (HDO) reactions are popular pathways
within biomass refining and medicinal chemistry to obtain
derivatives of oxygen-rich precursors.[29] While HDO treatment of
13 failed to yield the corresponding 2,4-substitution pattern,
conversion of the bromine by means of SMR prior to HDO
treatment allowed for the synthesis of a 2,4-substitution pattern
in 14 (Scheme 1).[29a] Further substitution patterns were
accessible from dibenzofuran-4-ol (20). The starting material for
the sequence was obtained in 94
%
yield from the
corresponding boronic acid 18 by oxidation (Scheme 2).[25]
Triflate formation of the phenol yielded compound 19. Its
subsequent bromination resulted in a 4,8-substitution pattern in
23. According to crude 1H NMR, the yield of this conversion was
in the range of 90 - 94 %. In contrast to dibenzofuran-1-ol (1),
bromination of dibenzofuran-4-ol (20) using NBS in DCM
required low reaction temperatures in order to obtain the bi-
functionalized product 24. Trace amounts of 1-bromo-
dibenzofuran-4-ol (22) were also isolated. Thus, double
bromination occurred to a small extent, too. Due to the limited
solubility of the starting material, it was not possible to decrease
the reaction temperature below -10 °C.
Scheme 2. Bi- or tri-functionalized building blocks derived from dibenzofuran-4-ol. R1 = diphenyltriazine.
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The introduction of a TIPS group in 20, bromination of the
corresponding 21 in THF and subsequent removal of the TIPS
group allowed for the synthesis of a 1,4-substitution pattern with
bromine in the 1-position, i.e. 22.[8, 27a] The acid-catalyzed
chlorination of 22 gave the tri-functionalized 25. Once more, the
conversion of the (halogen-)dibenzofuranol species 22, 24 and
25 yielded 73 - 96 % of the corresponding triflates 26, 27 and 28
using standard reaction conditions (Tf2O, NEt3, DCM). Thus, the
bromo-selective borylation of the 1,3,4-functionalized inter-
mediate 28 to 29 was possible. A 1,3-substitution pattern was
achievable by further derivatization of 29 by SMR reaction with
2-chloro-4,6-biphenyl-[1,3,5]-triazin and subsequent HDO
treatment to yield 30.[29a]
Bi-functional bromo aryl triflates are interesting substrates for
selective mono substitutions by means of SMR. Using 5 and the
commercially available boronic acid 31 as model system, we
investigated reaction conditions for both mono substituted
products 32 and 33 (Table 2). Literature protocols using PPh3 or
PtBu3 as ligand did not give satisfactory yields on our
substrate.[15, 18] While SPhos and XPhos gave product mixtures
with preference for 33, PCy3, CataCXium A and the precatalyst
Pd-PEPPSI-iPr gave product mixtures in favor of 32. P(o-Tol)3
was the most suitable ligand for a bromine selective coupling,
giving 32 in 80 % yield. In contrast, triflate selective coupling to
33 worked best with dppb as ligand (92 % yield).
In order to evaluate the generality of these findings,
regioisomers of 5 were subjected to bromine and triflate
selective SMR reaction conditions. For bromine selective SMRs,
the desired products were obtained in varying yields (Table 3).
Simple bromo aryl triflates were investigated and gave an
excellent selectivity for the bromine converted coupling products.
Hence, the developed bromine-selective SMR conditions have a
broader application. The high selectivity of the system
Pd2dba3 / P(o-Tol)3 may be a result of the fast formation of a
dimeric
Pd-ligand-complex and aryl bromide at room temperature, which
is mediated through monophosphine intermediate as
oxidative
addition
product
between
the
a
demonstrated by Hartwig and co-workers. This mechanism is
attributed to the steric bulk of P(o-Tol)3 that disfavors a direct
reaction of the haloarene with PdL2, but facilitates ligand
dissociation to highly reactive PdL species. In contrast to that,
complexes including the sterically less hindered PPh3 form
monomeric addition products.[30]
Table 3. Bromine-selective Suzuki-Miyaura reactions.
ArOTfBr
Boronic Acid
Product
Yield [%]
Entry
1[a]
6
31
50
Table 2. Catalyst screening for the selective synthesis of 32 and 33,
respectively.
2[b]
9
31
31
Area Percentage [%]
Catalytic system (ratio)
Entry
5
32
33
Pd(PPh3)4
2
52
33
1
2
3[c]
78
81
Pd2dba3 / PPh3 (1:2)
Pd2dba3 / P(o-Tol)3 (1:2)
Pd2dba3 / SPhos (1:2)
Pd2dba3 / XPhos (1:2)
Pd2dba3 / CMPhos (1:2)
Pd2dba3 / PCy3 (1:2)
Pd2dba3 / P(t-Bu)3 (1:2)
Pd2dba3 / CataCXium A (1:2)
Pd-PEPPSI-iPr
2
0
52
80
11
24
6
31
3
3
4[c]
37
37
5
73
61
5
4
4
5
18
3
6
5[c]
70
7
11
1
7
95
3
8
0
74
73
0
9
9
Reaction conditions: 0.6 mmol ArOTfBr, 0.6 mmol boronic acid, 1.8 mmol
Na2CO3, 1 mol-% Pd2dba3, 4 mol-% P(o-Tol)3, 5 ml toluene, 1 ml water,
90 °C, 16 h. Area percentage determined by HPLC. The amount of boronic
acid could not be assigned due to co-elution with toluene. [a] The main side
reaction is a hydrodeborylation of the boronic acid. [b] The reaction showed
incomplete conversion. [c] Area percentage determined by GC-MS.
0
12
92
10
11[a]
Pd2dba3 / dppb (1:4)
2
Reaction conditions: 1.27 mmol 5, 1.52 mmol 31, 2.53 mmol K2CO3,
1 mol-% [Pd], 5.75 ml toluene, 2 ml water, 90 °C, 16 h. Area percentage
determined by HPLC. The amount of remaining boronic acid could not be
assigned due to co-elution with toluene. [a] Area percentage determined
by GC-MS.
The developed triflate selective SMR reaction conditions proved
to be suitable for bromo dibenzofuran triflates (Table 4). Simple
bromo aryl triflates gave mixtures of triflate-, bromine- and
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doubly substituted products. In general, dppb as a bulky
phosphine can accelerate the rate of oxidative addition
regarding triflates due to the formation of a coordinatively
unsaturated and hence electron rich Pd(0) species.[14] Thus,
oxidative addition of triflates to Pd(0) complexes is reported to
be faster when electron withdrawing groups are present within
the aryl triflate.[31] This could be
a
reason why bromo
dibenzofuran triflates allow for a triflate selective Suzuki coupling.
Table 4. Triflate-selective Suzuki-Miyaura reactions.
ArOTfBr
Boronic Acid
Product
Main side products
Yield [%]
Entry
1[a]
6
31
/
85
2
9
31
83.8 / 5.7
3
26
31
/
85
4[b,c]
36
39
37
37
0.4 / 49.1 / 32.7
57.1 / 30.9 / 8.8
5[c]
6[b,c]
41
37
31.8 / 29.0 / 18.4
Reaction conditions: 0.6 mmol ArOTfBr, 0.6 mmol boronic acid, 1.8 mmol Na2CO3, 1 mol-% Pd2dba3, 4 mol-% dppb, 5 ml toluene, 1 ml water, 90 °C, 16 h. Area
percentage determined by HPLC. The amount of boronic acid could not be assigned due to co-eluation with toluene. [a] K2CO3 was used. [b] The reaction showed
incomplete conversion. [c] Area percentage determined by GC-MS.
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1
Hertz [Hz]. Resonance multiplicity of signals are: s = singlet, d = doublet,
t = triplet, q = quartet, m = multiplet, bs = broad singlet, dd = doublet of
doublets, dt = doublet of triplets and further combinations thereof. High
resolution mass spectra (HR-MS) were obtained from the analytical
department of Merck KGaA, Darmstadt. Melting points were measured
on a Büchi Melting Point B-540. Compounds 38,[33] 40,[33b] 42,[34] 48,[35]
The H NMR resonance signals, e.g. of compound 2, illustrate
an electron deficiency of the 9-position (8.04 ppm) that is caused
by the electron withdrawing properties of the “enol ether”
inherent in the hetero aromatic core (Figure 1).
50[36] and 52[37] are literature-known. Therefore, merely GC-MS
measurements were conducted to confirm their formation during the
reactions.
Figure 1. 1H NMR chemical shifts of triflate 2 in DMSO-d6.
2.
Synthesis
General procedure A for the triflate formation of a phenol derivative
The phenol compound (1 equiv.) was suspended in anhydrous DCM
(100 - 130 equiv.), followed by the addition of NEt3 (3 equiv.). The
mixture was cooled with an ice bath to an inner temperature of 0 - 4 °C.
Tf2O (1.2 - 1.5 equiv.) was added dropwise, so that the inner temperature
stayed below 10 °C. The mixture was allowed to warm to room
temperature overnight. For an aqueous workup, the mixture was washed
with water once, with 1M HCl twice and with water twice. The organic
layer was dried over anhydrous sodium sulfate, filtered and concentrated
to give crude that was purified by column chromatography on silica gel or
crystallization from an appropriate solvent.
Conclusions
In summary, two dibenzofuranols as starting materials allowed
for the synthesis of bi- and tri-substituted building blocks with ten
different substitution patterns. The choice of reaction sequence
regarding halogenation, derivatization, triflate formation and
HDO proved to be essential to control the formed substitution
patterns. Halogenation of phenol compounds and their TIPS
masked derivatives rendered
a
highly regioselective
functionalization possible within the already substituted subunit,
while triflate formation and subsequent halogenation resulted in
a substitution of the so far unfunctionalized subunit. HDO
treatment could remove the directing phenol function in form of
its triflate derivative. The developed synthetic protocols proved
to be highly selective, robust and scalable to large quantities in
high yields with a simple mode of operation. Hence, a large
library of diverse functionalized dibenzofuran building blocks
was synthesized in few steps. Limitations of previously reported
synthetic protocols, such as low selectivity and yield were
overcome. The first synthesis of 2-bromo-dibenzofuran-1-ol,
4-bromo-dibenzofuran-1-ol and tri-functionalized dibenzofurans
illustrate the variety of accessible substituted dibenzofurans. For
bi-functional intermediates bearing a triflate and a bromine
function, a functional group selective Suzuki-Miyaura cross
coupling was possible by appropriate choice of the ligand. The
catalytic system of Pd2dba3 / P(o-Tol)3 in combination with
carbonate bases in toluene / water mixtures allowed for the
bromine selective SMR of bromo aryl triflates including
dibenzofuran derivatives. In contrast, replacement of P(o-Tol)3
with dppb allowed for the triflate selective Suzuki-Miyaura
coupling of bromo dibenzofuran triflates. The ease of synthetic
accessibility of diverse functionalized dibenzofuran building
blocks in combination with their highly selective cross coupling
by means of SMR enables a multifold structural diverse access
to extended aromatic systems for various applications.
General procedure B for the bromination of a triflate derivative
TfOH (1.2 equiv.) was added to a solution of the triflate derivative
(1 equiv.) in anhydrous DCM (100 equiv.). NBS (1 equiv.) was added
portion wise at 18 - 20 °C. The mixture was stirred until complete
consumption of the starting material. Afterwards, the mixture was washed
with saturated NaHCO3 solution once and with water twice. The organic
layer was dried over anhydrous sodium sulfate, filtered and concentrated
to give crude that was either purified by column chromatography or
crystallized from an appropriate solvent.
General procedure C for the bromine-selective borylation of a bi- or
tri-functionalized dibenzofuran
The bi- or tri-functionalized starting material (1 equiv.), KOAc (2.5 equiv.)
and B2pin2 (1 equiv.) were suspended in anhydrous toluene
(92 - 98 equiv.). The mixture was saturated with argon for 1 h.
Pd(dppf)Cl2 (1 mol-%) was added and the mixture was stirred at 80 °C
until complete consumption of the starting material was monitored by
TLC or 1H NMR. After cooling to room temperature, the mixture was
washed with water three times, the organic layer was dried over
anhydrous sodium sulfate, filtered and concentrated. The crude was
suspended in cyclohexane or n-heptane and stirred at room temperature
for at least 5 h. The solid was collected by filtration, washed with solvent
and dried in vacuo at 50 °C to give a solid.
General procedure
reaction
D for the bromine-selective Suzuki-Miyaura
Bromo aryl triflate (0.6 mmol, 1 equiv.), boronic acid (0.6 mmol, 1 equiv.),
Na2CO3 (1.8 mmol, 3 equiv.), Pd2dba3 (1 mol-%) and P(o-Tol)3 (4 mol-%)
were suspended in toluene (5 ml) and water (1 ml). The mixture was
saturated with argon for 5 min, then stirred at 80 °C for 16 h. The mixture
was concentrated in vacuo and purified by column chromatography to
obtain the corresponding product.
Experimental Section
General procedure
coupling
E for the triflate-selective Suzuki-Miyaura
1.
General Information
Reagents, solvents and compounds 1, 2 and 18 were purchased from
commercial suppliers (Sigma Aldrich, Merck, VWR, Valiant) and used
without further purification. All reactions were carried out under argon
atmosphere. The use of dry solvents is indicated. Silica gel coated
aluminum plates (Merck silica gel 60 F254) were used for reaction
monitoring by TLC analysis. UV detection was carried out at 254 and
366 nm.
Bromo aryl triflate (0.6 mmol, 1 equiv.), boronic acid (0.6 mmol, 1 equiv.),
Na2CO3 (1.8 mmol, 3 equiv.), Pd2dba3 (1 mol-%) and dppb (4 mol-%)
were suspended in toluene (5 ml) and water (1 ml). The mixture was
saturated with argon for 5 min, then stirred at 80 °C for 16 h. The mixture
was concentrated in vacuo and purified by column chromatography to
obtain the corresponding product.
NMR spectra were recorded on a Bruker Advance II+ 500 MHz (1H
500 MHz, 13C 126 MHz, 19F 471 MHz) or Bruker Avance III (1H 700 MHz,
13C 176 MHz). All spectra were recorded at 298 K unless stated
otherwise. Chemical shifts are reported in ppm relative to an internal
standard (solvent residual peak),[32] coupling constants J are reported in
2-Bromo-dibenzofuran-1-ol (3)
Dibenzofuran-1-ol (1) (100 g, 533 mmol, 1 equiv.) was dissolved in
anhydrous DCM (2.55 l). NBS (97.5 g, 533 mmol, 1 equiv.) was added at
an inner temperature of 15 °C within 75 min. After stirring at room
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10.1002/ejoc.201801286
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temperature for 30 min, the mixture was washed with water three times,
dried over anhydrous sodium sulfate, filtered and concentrated. The
received solid was suspended in n-heptane (1.00 l) and stirred at 60 °C
for 30 min, then at room temperature before collected by filtration. The
protocol was repeated two times. The received products were combined
(322 g grey solid), suspended in n-heptane (2.00 l) and stirred at 85 °C
for 18 h. After cooling to room temperature, the now beige solid was
collected by filtration and dried in vacuo to give a first fraction of the title
compound (229 g, 871 mmol, 54 % yield). The mother liquor was
concentrated to give a second fraction of the product, which was further
Trifluoromethanesulfonic acid 8-bromo-2-phenyl-dibenzofuran-1-yl
ester (7)
2-Phenyl-dibenzofuran-1-ol (7a)
2-Bromo-dibenzofuran-1-ol (3) (100 g, 319 mmol, 1 equiv.), phenyl
boronic acid (40.9 g, 335 mmol, 1.05 equiv.) and K2CO3 (132 g,
957 mmol, 3 equiv.) were dissolved in toluene (2.50 l) and water (500 ml).
The mixture was saturated with argon for 1 h, then Pd2dba3 (2.92 g,
3.19 mmol, 1 mol-%) and SPhos (5.24 g, 12.7 mmol, 4 mol-%) were
added and the reaction was stirred at reflux for 22 h. After cooling to
room temperature, the aqueous layer was carefully acidified with 1M HCl
and extracted with toluene. The combined organic layers were washed
with water, dried over anhydrous sodium sulfate, filtered and
concentrated to give a pale yellow oil (80.1 g, 258 mmol, 81 %).
1H NMR (500 MHz, TCE-d2) δ 8.18 (dd, J = 7.6, 1.3 Hz, 1H), 7.60 (d,
J = 8.1 Hz, 1H), 7.59 - 7.53 (m, 4H), 7.48 (m, 2H), 7.40 (td, J = 7.5, 1.0
Hz, 1H), 7.37 (d, J = 8.3 Hz, 1H), 7.26 (d, J = 8.3 Hz, 1H), 5.96 (s, 1H).
13C NMR (126 MHz, TCE-d2) δ 156.9, 155.6, 148.0, 136.2, 130.0 (2C),
129.6 (2C), 129.2, 128.9, 126.4, 123.3, 122.9, 122.7, 121.9, 112.5, 111.0,
104.0. HR-GC-MS (TOF MS+) calculated for C18H12O2 [M+]: 260.0837,
found 260.0837.
purified by
a hot extraction (600 ml n-heptane/toluene 8:1). The
precipitated solid was collected by filtration and dried in vacuo (119 g,
452 mmol, 28 % yield). In total, a yield of 82 % was achieved. 1H NMR
(500 MHz, DMSO-d6) δ 10.23 (s, 1H), 8.15 (dd, J = 7.6, 1.2 Hz, 1H), 7.68
(dt, J = 8.3, 0.8 Hz, 1H), 7.61 (d, J = 8.7 Hz, 1H), 7.51 (ddd, J = 8.5, 7.2,
1.4 Hz, 1H), 7.42 (td, J = 7.5, 1.0 Hz, 1H), 7.20 (d, J = 8.6 Hz, 1H). 13C
NMR (101 MHz, DMSO-d6) δ 155.7, 155.0, 149.3, 131.0, 127.1 (2C),
123.2, 122.5, 114.5, 111.3, 105.1, 103.7. HR-GC-MS (TOF MS+)
calculated for C12H7O2Br [M+]: 261.9629, found 261.9636. Melting
point: 122 °C.
(Dibenzofuran-1-yloxy)-triisopropyl-silane (4)
Trifluoromethanesulfonic acid 2-phenyl-dibenzofuran-1-yl ester (7b)
The compound was prepared by following general procedure A using
2-phenyl-dibenzofuran-1-ol (7a) (61.7 g, 232 mmol, 1 equiv.), anhydrous
DCM (800 ml), NEt3 (100 ml, 721 mmol, 3.1 equiv.) and Tf2O (50.0 ml,
303 mmol, 1.3 equiv.). The crude was filtered over silica gel and washed
with DCM to give oil that crystallized to a white solid upon standing at air
(93.9 g, 97 %, 232 mmol, 100 % yield). The reaction was repeated two
times. 1H NMR (500 MHz, DMSO-d6) δ 8.17 (dt, J = 7.8, 1.1 Hz, 1H),
7.99 (d, J = 8.5 Hz, 1H), 7.87 (dt, J = 8.4, 0.8 Hz, 1H), 7.74 (d, J = 8.5 Hz,
1H), 7.69 (ddd, J = 8.5, 7.3, 1.3 Hz, 1H), 7.62 - 7.59 (m, 2H), 7.58 - 7.55
(m, 1H), 7.55 - 7.51 (m, 2H), 7.48 (dd, J = 7.3, 1.4 Hz, 1H). 13C NMR
(101 MHz, DMSO-d6) δ 155.8, 155.6, 138.9, 135.0, 130.9, 130.3, 129.6
(2C), 129.1, 128.6 (2C), 128.3, 123.9, 122.2, 120.3, 118.3, 117.4 (q,
J = 321 Hz), 113.0, 112.3. 19F NMR (471 MHz, DMSO-d6) δ -73.94.
HR-GC-MS (TOF MS+) calculated for C19H11O4F3S [M+]: 392.0330,
found 392.0318. Melting point: 98 °C.
Dibenzofuran-1-ol (1) (82.0 g, 439 mmol, 1 equiv.) was dissolved in
anhydrous DCM (2.00 l). Imidazole (59.7 g, 877 mmol, 2 equiv.) was
added, followed by chlorotriisopropylsilane (105 ml, 479 mmol,
1.1 equiv.). The reaction was stirred at room temperature for 21 h. The
reaction mixture was washed with water once, with 20 % NaOH twice
and once again with water. The organic layer was dried over anhydrous
sodium sulfate, filtered and concentrated. The product was received as
brown oil in a mixture with triisopropylsilanol (171.2 g, 87 %, 437 mmol,
99 % yield). 1H NMR (500 MHz, DMSO-d6) δ 8.07 (ddd, J = 7.6, 1.4,
0.6 Hz, 1H), 7.69 (dt, J = 8.4, 0.8 Hz, 1H), 7.52 - 7.47 (m, 1H), 7.42 (td,
J = 7.4, 1.0 Hz, 1H), 7.40 (t, J = 8.3 Hz, 1H), 7.29 (dd, J = 8.3, 0.7 Hz,
1H), 6.85 (dd, J = 8.1, 0.7 Hz, 1H), 1.46 (hept, J = 7.5 Hz, 3H), 1.14 (s,
9H), 1.13 (s, 9H). 13C NMR (126 MHz, DMSO-d6) δ 156.9, 154.7, 151.5,
128.4, 126.7, 123.1, 122.8, 121.8, 114.7, 111.9, 111.4, 104.6, 17.8 (6C),
12.6 (3C). HR-GC-MS (TOF MS+) calculated for C21H28O2Si [M+]:
340.1859, found 340.1849.
Trifluoromethanesulfonic acid 8-bromo-2-phenyl-dibenzofuran-1-yl ester
(7)
Trifluoromethanesulfonic acid 8-bromo-dibenzofuran-1-yl ester (5)
The compound was prepared by following general procedure B using
triflate 2 (100 g, 316 mmol, 1 equiv.), anhydrous DCM (1.00 l), TfOH
(33.3 ml, 379 mmol, 1.2 equiv.) and NBS (56.3 g, 316 mmol, 1 equiv.)
suspended in anhydrous DCM (250 ml). The reaction was completed
within 22 h. The crude was suspended in ethanol (300 ml) at room
temperature, collected by filtration and dried in vacuo at 50 °C to give a
beige solid (101 g, 256 mmol, 81 % yield). 1H NMR (500 MHz, DMSO-d6)
δ 8.11 (dd, J = 1.8, 0.8 Hz, 1H), 7.95 (dd, J = 8.4, 0.6 Hz, 1H), 7.88 - 7.83
The compound was prepared by following general procedure B using
compound 7b (93.3 g, 97 %, 231 mmol, 1 equiv.), TfOH (25 ml,
284 mmol, 1.2 equiv.) and anhydrous DCM (800 ml, 54 equiv.). NBS
(41.2 g, 231 mmol, 1 equiv.) suspended in anhydrous DCM (400 ml,
27 equiv.) was added dropwise at an inner temperature of 8 - 10 °C. The
mixture was allowed to warm to room temperature and stirred for 18 h
while monitored by 1H-NMR. The mixture was again cooled to 8 - 10 °C
to add another portion of NBS (8.24 g, 46.3 mmol, 0.2 equiv.) in
anhydrous DCM (100 ml, 6.8 equiv.) dropwise. The reaction was
completed within one hour. After the aqueous work-up, the crude (109 g)
was crystallized from cyclohexane (370 ml) to give a light beige solid
(87.5 g, 176 mmol, 76 % yield). 1H NMR (500 MHz, DMSO-d6) δ 8.27 (d,
J = 1.8 Hz, 1H), 8.03 (d, J = 8.6 Hz, 1H), 7.89 - 7.86 (m, 2H), 7.79 (d,
J = 8.5 Hz, 1H), 7.63 - 7.57 (m, 2H), 7.54 (t, J = 7.5 Hz, 2H), 7.49 (tt,
J = 7.2, 1.5 Hz, 1H). 13C NMR (126 MHz, DMSO-d6) δ 156.0, 154.8,
138.8, 134.8, 131.9, 131.7, 130.7, 129.7 (2C), 128.7 (2C), 128.5, 124.6,
122.4, 117.4 (q, J = 321 Hz), 117.3, 115.7, 114.6, 113.4. 19F NMR
(471 MHz, DMSO-d6) δ -73.89. HR-LC-MS (LC-APCI-MS) calculated for
C19H10BrF3O4S [M+H+]: 469.9430, found 469.9431. Melting point:
131 °C.
(m, 2H), 7.78 (t,
J = 8.3 Hz, 1H), 7.57 (d, J = 8.3 Hz, 1H).
13C NMR (126 MHz, DMSO-d6) δ 156.9, 154.3, 142.5, 131.6, 129.7,
124.0, 122.0, 118.1 (q, J = 320.8 Hz), 116.1, 115.8, 115.7, 114.5, 113.0.
19F NMR (471 MHz, DMSO-d6) δ -72.98. HR-GC-MS (TOF MS+)
calculated for C13H6O4F3SBr [M+]: 393.9122, found 393.9139. Melting
point: 98 °C.
Trifluoromethanesulfonic acid 2-bromo-dibenzofuran-1-yl ester (6)
The compound was prepared by following general procedure A using
compound 3 (100 g, 339 mmol, 1 equiv.), anhydrous DCM (2.00 l), NEt3
(141 ml, 1.01 mol, 3 equiv.) and Tf2O (67.3 ml, 407 mmol, 1.2 equiv.).
After 17 h, the mixture was again cooled to 0 °C to add another portion of
Tf2O (14.0 ml, 84.7 mmol, 0.25 equiv.) dropwise. The reaction was
completed within 5 h. After the aqueous work-up, the crude (139 g brown
oil) was filtered over silica gel (SiO2, Hep) to give a main fraction of the
title compound as a white solid (87.9 g, 222 mmol, 65 % yield) and
another fraction as a yellow solid (15.5 g, 94 % product content,
36.8 mmol, 11 % yield). In total, a yield of 76 % was achieved. 1H NMR
(500 MHz, DMSO-d6) δ 8.08 (dt, J = 8.0, 0.9 Hz, 1H), 8.00 (d, J = 8.7 Hz,
1H), 7.89 (d, J = 8.7 Hz, 1H), 7.84 (dt, J = 8.4, 0.8 Hz, 1H), 7.69 (ddd,
J = 8.4, 7.3, 1.3 Hz, 1H), 7.55 (ddd, J = 8.1, 7.4, 1.0 Hz, 1H). 13C NMR
(126 MHz, DMSO-d6) δ 155.8, 155.6, 138.8, 132.4, 129.7, 124.1, 122.3,
119.6, 119.4, 118.0 (q, J = 321 Hz), 114.4, 112.4, 109.2. 19F NMR
(471 MHz, DMSO-d6) δ -72.07. HR-GC-MS (TOF MS+) calculated for
C13H6O4SBrF3 [M+]: 393.9122, found 393.9140. Melting point: 88 °C.
4-Bromo-dibenzofuran-1-ol (8)
(Dibenzofuran-1-yloxy)-triisopropylsilane (4) (90.2 g, 87 %, 231 mmol,
1 equiv.) was dissolved in anhydrous THF (2.00 l). NBS (41.1 g,
231 mmol, 1 equiv.) was added to the orange solution at room
temperature. The now red solution was stirred at room temperature for
17 h. After reaction control by 1H NMR, another portion of NBS (5.34 g,
30.0 mmol, 0.13 equiv.) was added. After 23 h, CsF (45.6 g, 300 mmol,
1.3 equiv.) was added. After 19 h, the same amount of CsF was added
again. After another 6 h, the solvent was removed, the residue was
dissolved in toluene and water. The aqueous layer was acidified with 1M
HCl to pH 2-3 and extracted with toluene twice. The combined organic
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201801286
European Journal of Organic Chemistry
FULL PAPER
layers were washed with water twice, then dried over anhydrous sodium
sulfate, filtered and concentrated. The crude (203 g orange solid with an
unpleasant smell) was suspended in cyclohexane (300 ml) and stirred at
room temperature over night. The light beige solid was collected by
filtration, washed with cyclohexane and dried in vacuo at 50 °C (53.7 g,
204 mmol, 88 % yield). 1H NMR (500 MHz, DMSO-d6) δ 10.81 (s, 1H),
8.07 (dd, J = 7.7, 1.3 Hz, 1H), 7.75 (d, J = 8.1 Hz, 1H), 7.51 (ddd, J = 8.4,
7.3, 1.4 Hz, 1H), 7.50 (d, J = 8.5 Hz, 1H), 7.42 (td, J = 7.5, 1.0 Hz, 1H),
6.79 (d, J = 8.6 Hz, 1H). 13C NMR (126 MHz, DMSO-d6) δ 154.4, 153.4,
153.3, 130.5, 126.9, 123.7 (2C), 123.2, 122.6, 111.4, 110.7, 91.8.
HR-GC-MS (TOF MS+) calculated for C12H7O2Br [M+]: 261.9629, found
261.9614. Melting point: 180 °C.
was added to the orange solution, followed by 10 drops 1M HCl. The
mixture was stirred at room temperature for 19 h. After reaction control
by TLC, another 15 drops 1M HCl were added. After another 24 h, the
solvent was removed, the residue was dissolved in excess DCM and
water. The aqueous layer was acidified with 1M HCl to pH 2-3 and
extracted with DCM once. The combined organic layers were washed
with water three times, dried over anhydrous sodium sulfate, filtered and
concentrated to give the title compound as beige solid (22.3 g, 96 %,
72.3 mmol, 95 % yield). 1H NMR (500 MHz, DMSO-d6) δ 10.76 (s, 1H),
8.15 (dd, J = 7.7, 1.3 Hz, 1H), 7.78 (d, J = 8.3 Hz, 1H), 7.77 (s, 1H), 7.57
(ddd, J = 8.5, 7.3, 1.4 Hz, 1H), 7.46 (td, J = 7.6, 1.0 Hz, 1H). 13C NMR
(126 MHz, DMSO-d6) δ 154.9, 152.1, 148.3, 129.6, 127.8, 123.9, 122.9,
122.8, 115.3, 115.0, 111.7, 93.1. HR-GC-MS (TOF MS+) calculated for
C12H6O2ClBr [M+]: 295.9240, found 295.9257. Melting point: 153 °C.
Trifluoromethanesulfonic acid 4-bromo-dibenzofuran-1-yl ester (9)
The compound was prepared by following general procedure A using
compound 8 (42.0 g, 160 mmol, 1 equiv.), anhydrous DCM (1.00 l), NEt3
(66.4 ml, 479 mmol, 3 equiv.) and Tf2O (34.3 ml, 207 mmol, 1.3 equiv.).
The crude was filtered over silica gel (SiO2, cyclohexane/THF 9:1) and
concentrated to give the title compound as a beige solid (60.1 g,
152 mmol, 95 % yield). 1H NMR (500 MHz, DMSO-d6) δ 8.02 (d,
J = 7.7 Hz, 1H), 7.96 (d, J = 8.6 Hz, 1H), 7.94 (d, J = 7.9 Hz, 1H), 7.73
(ddd, J = 8.4, 7.3, 1.3 Hz, 1H), 7.59 (td, J = 7.5, 0.9 Hz, 1H), 7.50 (d,
J = 8.7 Hz, 1H). 13C NMR (126 MHz, DMSO-d6) δ 155.3, 153.4, 141.9,
131.1, 129.8, 124.8, 122.1, 120.1, 118.0, 117.4, 118.1 (q, J = 321 Hz),
112.6, 104.3. 19F NMR (471 MHz, DMSO-d6) δ -72.85. HR-GC-MS (TOF
MS+) calculated for C13H6O4F3SBr [M+]: 393.9122, found 393.9128.
Melting point: 77 °C.
Trifluoromethanesulfonic acid 4-bromo-2-chloro-dibenzofuran-1-yl
ester (13)
The compound was prepared by following general procedure A using
compound 12 (21.9 g, 96 %, 70.9 mmol, 1 equiv.), anhydrous DCM
(560 ml), NEt3 (29.5 ml, 213 mmol, 3 equiv.) and Tf2O (17.6 ml,
106 mmol, 1.5 equiv.). The brown crude (36 g) was dissolved in
cyclohexane (500 ml) at 60 °C, then filtered over silica gel and washed
with cyclohexane. The pale yellow filtrate was concentrated to give the
title compound as a white solid (28.3 g, 65.9 mmol, 93 % yield). 1H NMR
(500 MHz, DMSO-d6) δ 8.28 (s, 1H), 8.06 (dt, J = 8.0, 0.9 Hz, 1H), 7.93
(d, J = 8.4 Hz, 1H), 7.75 (ddd, J = 8.5, 7.3, 1.3 Hz, 1H), 7.59 (ddd, J = 8.1,
7.4, 0.9 Hz, 1H). 13C NMR (126 MHz, DMSO-d6) δ 155.8, 152.3, 136.9,
131.1, 130.3, 124.7, 122.5, 121.3, 119.9, 119.8, 118.0 (q, J = 321 Hz),
112.7, 105.2. 19F NMR (471 MHz, DMSO-d6) δ -72.12. HR-GC-MS (TOF
MS+) calculated for C13H5O4F3SClBr [M+]: 427.8733, found 427.8742.
Melting point: 109 °C.
Trifluoromethanesulfonic
acid
8-(4,4,5,5-tetramethyl-
[1,3,2]dioxaborolan-2-yl)-dibenzo-furan-1-yl ester (10)
The compound was prepared by following general procedure C using
compound 5 (100 g, 246 mmol, 1 equiv.), KOAc (60.3 g, 614 mmol,
2.5 equiv.), B2pin2 (83.0 g, 327 mmol, 1.3 equiv.), toluene (2.4 l) and
Pd(dppf)Cl2 (2.70 g, 3.69 mmol, 1.5 mol-%). The crude (118 g) was
dissolved in cyclohexane (300 ml), stirred at room temperature over night,
collected by filtration and dried in vacuo over night at 50 °C to yield a
beige solid (60.7 g, 137 mmol, 56 %). 1H NMR (500 MHz, DMSO-d6) δ
8.44 (t, J = 0.9 Hz, 1H), 7.94 (dt, J = 8.3, 1.0 Hz, 2H), 7.84 (dd, J = 8.4,
0.7 Hz, 1H), 7.74 (t, J = 8.3 Hz, 1H), 7.56 (d, J = 8.3 Hz, 1H), 1.34 (s,
12H). 13C NMR (126 MHz, DMSO-d6) δ 157.5, 156.5, 142.7, 135.9, 129.0,
128.4, 119.8, 118.1 (q, J = 321 Hz), 116.4, 116.0 (2C), 112.8, 111.9, 83.9
(2C), 24.7 (4C). 19F NMR (471 MHz, DMSO-d6) δ -73.08. HR-LC-MS
(LC-APLI-MS) calculated for C19H18BF3O6S [M+H+]: 442.0877, found:
442.0877. Melting point: 125 °C.
3-(2-Chloro-dibenzofuran-4-yl)-9-phenyl-9H-carbazole (14)
Trifluoromethanesulfonic acid 2-chloro-4-(9-phenyl-9H-carbazol-3-yl)-
dibenzofuran-1-yl ester (14a)
The compound was prepared by following general procedure D using
compound 13 (1.00 g, 2.33 mmol and appropriate equivalents of
reagents and solvents). The reaction was stirred at 90 °C for 15 h. After
cooling to room temperature, the mixture was diluted with toluene and
washed with water three times. The organic layer was dried over
anhydrous sodium sulfate, filtered and concentrated. The crude was
purified by column chromatography (SiO2, n-heptane/THF 95:5  90:10)
to give a yellow oil (720 mg, 1.22 mmol, 52 % yield). 1H NMR (700 MHz,
THF-d8) δ 8.77 (d, J = 1.8 Hz, 1H), 8.30 (dd, J = 7.9, 1.1 Hz, 1H), 8.28 (d,
J = 7.7 Hz, 1H), 8.04 (s, 1H), 8.02 (dd, J = 8.5, 1.8 Hz, 1H), 7.75 (d,
J = 8.3 Hz, 1H), 7.71 - 7.66 (m, 4H), 7.64 (td, J = 8.3, 7.8, 1.2 Hz, 1H),
7.57 (d, J = 8.5 Hz, 1H), 7.54 (tt, J = 6.7, 1.9 Hz, 1H), 7.50 (t, J = 7.6 Hz,
1H), 7.45 - 7.40 (m, 2H), 7.30 (ddd, J = 7.9, 5.1, 2.9 Hz, 1H). 13C NMR
(176 MHz, THF-d8) δ 157.9, 153.7, 142.6, 142.2, 138.6, 137.9, 131.1
(2C), 130.3, 129.8, 129.2, 128.8, 128.2 (2C), 128.0, 127.4, 126.7, 125.1,
124.8, 123.8, 122.5, 122.1, 121.8, 121.5, 121.5, 121.4, 119.9 (q,
J = 321Hz), 113.2, 111.0, 110.9. 19F NMR (471 MHz, THF-d8) δ -75.35.
HR-LC-MS (LC-APLI-MS) calculated for C31H18ClF3NO4S [M+H+]:
592.0583, found 592.0594. Melting point: 109 °C.
Trifluoromethanesulfonic
acid
2-phenyl-8-(4,4,5,5-tetramethyl-
[1,3,2]dioxaborolan-2-yl)-dibenzofuran-1-yl ester (11)
The compound was prepared by following general procedure C using
compound 7 (81.8 g, 174 mmol, 1 equiv.), B2pin2 (44.1 g, 174 mmol,
1 equiv.), KOAc (42.6 g, 434 mmol, 2.5 equiv.), anhydrous toluene
(2.00 l) and Pd(dppf)Cl2 (635 mg, 0.87 mmol, 0.5 mol-%). After stirring at
80 °C for 87 h, another portion of B2pin2 (5.29 g, 20.8 mmol, 0.12 equiv.)
was added. The reaction was finished after another 23 h. The reddish-
brown oil (100 g) received from the aqueous work-up was treated with
n-pentane (100 ml) and stored in the refrigerator overnight. The
crystallized beige solid was collected by filtration, washed with n-pentane
and dried in vacuo at 60 °C (89.4 g). The product was further purified by
crystallization from cyclohexane (300 ml) to give the title compound as a
sandy solid (72.4 g, 130 mmol, 93 % product content accompanied by
cyclohexane, 75 % yield). 1H NMR (500 MHz, DMSO-d6) δ 8.60 (t,
J = 0.9 Hz, 1H), 8.01 (d, J = 8.5 Hz, 1H), 7.95 (dd, J = 8.3, 1.2 Hz, 1H),
7.86 (dd, J = 8.3, 0.6 Hz, 1H), 7.75 (d, J = 8.5 Hz, 1H), 7.62 (dd, J = 8.2,
1.4 Hz, 2H), 7.54 (t, J = 7.4 Hz, 2H), 7.48 (tt, J = 7.2, 1.4 Hz, 1H), 1.34 (s,
12H). 13C NMR (126 MHz, DMSO-d6) δ 157.9, 155.6, 139.2, 135.1, 134.9,
131.1, 130.6, 129.7 (2C), 129.1, 128.7 (2C), 128.4, 120.3 (2C), 118.0,
118.7 (q, J = 321 Hz), 113.1, 111.9, 83.9 (2C), 24.7 (4C). 19F NMR
(471 MHz, DMSO-d6) δ -74.05. HR-LC-MS (LC-APCI-MS) calculated for
C25H23BF3O6S [M+H+]: 519.1255, found 519.1266. Melting point: 114 °C.
3-(2-Chloro-dibenzofuran-4-yl)-9-phenyl-9H-carbazole (14)
Compound 14a (540 mg, 0.91 mmol, 1 equiv.), Pd(OAc)2 (5.00 mg,
0.02 mmol, 2 mol-%) and dppp (9.57 mg, 0.02 mmol, 2 mol-%) were
dissolved in anhydrous DMF (10 ml). The mixture was saturated with
argon for 10 min, followed by the dropwise addition of triethylsilane
(0.36 ml, 2.28 mmol, 2.5 equiv.). The mixture was stirred at 60 °C for
2.5 h. After cooling to room temperature, the mixture was diluted with
toluene and washed with water three times. The organic layer was dried
over anhydrous sodium sulfate, filtered and concentrated to give a yellow
crude that was purified by column chromatography (SiO2, n-heptane/THF
99:1  98:2) to give a white solid (356 mg, 0.8 mmol, 87 % yield).
1H NMR (700 MHz, THF-d8) δ 8.76 (d, J = 1.8 Hz, 1H), 8.29 (d,
J = 7.6 Hz, 1H), 8.09 (dd, J = 7.7, 1.2 Hz, 1H), 8.04 (d, J = 2.1 Hz, 1H),
8.02 (dd, J = 8.5, 1.8 Hz, 1H), 7.81 (d, J = 2.1 Hz, 1H), 7.70 - 7.67 (m,
4H), 7.66 (d, J = 8.0 Hz, 1H), 7.55 (d, J = 8.5 Hz, 1H), 7.54 - 7.50 (m, 2H),
7.45 - 7.41 (m, 2H), 7.41 - 7.38 (m, 1H), 7.29 (ddd, J = 7.8, 6.3, 1.6 Hz,
1H). 13C NMR (176 MHz, THF-d8) δ 158.0, 153.0, 142.6, 141.9, 138.8,
138.3, 131.0 (2C), 129.7, 129.3, 129.0 (2C), 128.7, 128.1 (2C), 127.9,
4-Bromo-2-chloro-dibenzofuran-1-ol (12)
4-Bromo-dibenzofuran-1-ol (8) (20.0 g, 76.0 mmol,
1 equiv.) was
dissolved in anhydrous THF (650 ml). NCS (10.1 g, 76.0 mmol, 1 equiv.)
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201801286
European Journal of Organic Chemistry
FULL PAPER
127.5, 127.2, 125.0, 124.7, 124.6, 124.2, 122.1, 121.7, 121.5, 121.2,
119.6, 112.8, 110.8. HR-GC-MS (TOF MS+) calculated for C30H18NOCl
[M+]: 443.1077, found 443.1083. Melting point: 148 °C.
vacuo at 50 °C to give the title compound as a white solid without a
noticeable smell (72.6 g, 98 %, 270 mmol, 90 % yield). 1H NMR
(700 MHz, DMSO-d6) δ 10.53 (s, 1H), 8.42 (dd, J = 8.0, 1.3 Hz, 1H), 7.77
(d, J = 8.3 Hz, 1H), 7.61 (ddd, J = 8.3, 7.2, 1.3 Hz, 1H), 7.47 (t,
J = 7.7 Hz, 1H), 7.39 (d, J = 8.5 Hz, 1H), 6.95 (d, J = 8.5 Hz, 1H).
13C NMR (176 MHz, DMSO-d6) δ 155.3, 144.7, 142.7, 128.2, 127.0,
123.9, 123.4, 123.1, 121.8, 115.2, 111.9, 102.9. HR-GC-MS (TOF MS+)
calculated for C12H7O2Br [M+]: 261.9629, found 261.9634. Melting
point: 154 °C.
Trifluoromethanesulfonic acid dibenzofuran-4-yl ester (19)
The compound was prepared by following general procedure A using
compound 20 (2.76 g, 15.0 mmol, 1 equiv.), anhydrous DCM (50 ml),
NEt3 (6.30 ml, 45.5 mmol, 3 equiv.) and Tf2O (3.00 ml, 18.2 mmol,
1.2 equiv.). The mixture was stirred for 2 h, followed by the aqueous
work-up. The crude was purified by column chromatography (SiO2,
Hep/EE 99:1  92:8) to receive a pale yellow oil that crystallized to a
white solid upon standing at air (3.47 g, 10.9 mmol, 73 % yield). 1H NMR
(500 MHz, DMSO-d6) δ 8.30 (dd, J = 7.7, 1.0 Hz, 1H), 8.26 (d, J = 7.7 Hz,
1H), 7.84 (d, J = 8.2 Hz, 1H), 7.71 (dd, J = 8.2, 1.0 Hz, 1H), 7.63 (ddd,
J = 8.4, 7.3, 1.4 Hz, 1H), 7.55 (t, J = 8.0 Hz, 1H), 7.51 (td, J = 7.5, 0.9 Hz,
1H). 13C NMR (126 MHz, DMSO-d6) δ 155.8, 145.6, 133.2, 129.0, 127.3,
124.4, 124.2, 122.7, 122.0, 121.9, 120.3, 118.3 (q, J = 321 Hz), 112.1.
19F NMR (471 MHz, DMSO-d6) δ -72.99. HR-GC-MS (TOF MS+)
calculated for C13H7O4SF3 [M+]: 316.0017, found 316.0016. Melting
point: 63 °C.
Trifluoromethanesulfonic acid 8-bromo-dibenzofuran-4-yl ester (23)
The compound was prepared by following general procedure B using
compound 19 (158 mg, 0.5 mmol, 1 equiv.), anhydrous DCM (5 ml),
TfOH (53.0 µl, 0.6 mmol, 1.2 equiv.) and NBS (89 mg, 0.5 mmol,
1 equiv.). The mixture was stirred for 1 h at 18 - 19 °C. The reaction
mixture was concentrated and purified by column chromatography (SiO2,
Hep/EE 100:0  99:1). The title compound was received as colorless oil
(87 mg, 0.22 mmol, 44 % yield). 1H NMR (700 MHz, DMSO-d6) δ 8.56 (d,
J = 2.1 Hz, 1H), 8.33 (dd, J = 7.7, 1.0 Hz, 1H), 7.83 (d, J = 8.8 Hz, 1H),
7.77 (dd, J = 8.9, 2.3 Hz, 1H), 7.75 (d, J = 8.3 Hz, 1H), 7.57 (t, J = 8.0 Hz,
1H). 13C NMR (176 MHz, DMSO-d6) δ 154.7, 146.1, 133.1, 131.4, 126.3,
125.0, 124.8, 124.7, 122.6, 121.1, 118.2 (q, J = 321 Hz), 116.3, 114.2.
19F NMR (471 MHz, DMSO-d6) δ -72.93. HR-GC-MS (TOF MS+)
calculated for C13H6O4F3SBr [M+]: 393.9122, found 393.9085. Melting
point: 80 °C.
Dibenzofuran-4-ol (20)
Dibenzofuran-4-boronic acid (70.0 g, 330 mmol, 1 equiv.) was dissolved
in acetonitrile (1.00 l) and cooled in an ice bath. Urea hydrogen peroxide
(32.0 g, 330 mmol, 1 equiv.) was added portion wise to the white solution.
The mixture was stirred for 30 min and allowed to warm to room
temperature. The now yellowish solution was concentrated and dissolved
in toluene and water. The aqueous layer was acidified to pH 2-3 and
extracted with toluene three times. The organic layer was dried over
anhydrous sodium sulfate, filtered and concentrated to give a white solid
(60.6 g, 329 mmol, 99 % yield). 1H NMR (500 MHz, DMSO-d6) δ 10.19 (s,
1H), 8.08 (dd, J = 7.8, 1.4 Hz, 1H), 7.69 (d, J = 8.2 Hz, 1H), 7.54 (dd,
J = 7.7, 1.1 Hz, 1H), 7.50 (ddd, J = 8.3, 7.2, 1.4 Hz, 1H), 7.37 (td, J = 7.5,
0.9 Hz, 1H), 7.18 (t, J = 7.8 Hz, 1H), 6.97 (dd, J = 7.9, 1.0 Hz, 1H).
13C NMR (126 MHz, DMSO-d6) δ 155.3, 144.1, 143.0, 127.3, 125.2,
124.1, 123.7, 122.9, 121.1, 113.9, 111.7, 111.3. HR-GC-MS (TOF MS+)
calculated for C12H8O2 [M+]: 184.0524, found 184.0530. Melting point:
105 °C.
3-Bromo-dibenzofuran-4-ol (24)
Dibenzofuran-4-ol (3.00 g, 16.3 mmol, 1 equiv.) was dissolved in
anhydrous DCM (70 ml). The colorless solution was cooled to an inner
temperature of -12 °C. NBS (2.90 g, 16.3 mmol, 1 equiv.) suspended in
anhydrous DCM (70 ml) was added drop wise, so that the inner
temperature stayed below -8 °C. The mixture was allowed to warm to
room temperature over night. After reaction control by 1H-NMR, the
mixture was again cooled to -10 °C. Another portion of NBS (521 mg,
2.93 mmol, 0.18 equiv.) suspended in anhydrous DCM (15 ml) was
added dropwise. After warming to room temperature, the mixture was
washed with water three times. The organic layer was dried over
anhydrous sodium sulfate, filtered and concentrated. The crude was
purified by column chromatography (SiO2, Hep/EE 100:0  91:9) to
afford the title compound as a yellowish solid (2.68 g, 10.2 mmol, 62 %
yield). 1H NMR (500 MHz, DMSO-d6) δ 10.83 (s, 1H), 8.13 (ddd, J = 7.7,
1.3, 0.6 Hz, 1H), 7.72 (d, J = 8.2 Hz, 1H), 7.56 (d, J = 8.2 Hz, 1H), 7.55
(ddd, J = 8.4, 7.3, 1.4 Hz, 1H), 7.50 (d, J = 8.2 Hz, 1H), 7.42 (td, J = 7.5,
0.9 Hz, 1H). 13C NMR (101 MHz, DMSO-d6) δ 155.4, 144.8, 140.0, 127.8,
127.3, 124.5, 123.7, 123.3, 121.4, 112.6, 111.7, 108.5. HR-GC-MS (TOF
MS+) calculated for C12H7O2Br [M+]: 261.9629, found 261.9636. Melting
point: 134 °C.
(Dibenzofuran-4-yloxy)-triisopropyl-silane (21)
Dibenzofuran-4-ol (60.0 g, 325 mmol, 1 equiv.) was dissolved in
anhydrous DCM (1.50 l). Imidazole (44.3 g, 651 mmol, 2 equiv.) was
added, followed by chlorotriisopropylsilane (78.4 ml, 358 mmol,
1.1 equiv.). The reaction was stirred at room temperature for 18 h. The
precipitated white solid was collected by filtration and rejected after
washing with THF. The filtrate was washed with water once, with 20 %
NaOH three times and again with water twice. The solution was dried
over anhydrous sodium sulfate, filtered and concentrated to give the title
compound as pale orange oil (112 g, 91 %, 300 mmol, 92 % yield).
1H NMR (500 MHz, DMSO-d6) δ 8.11 (dd, J = 7.7, 1.2 Hz, 1H), 7.72 (dd,
J = 7.7, 1.1 Hz, 1H), 7.69 (d, J = 8.3 Hz, 1H), 7.52 (ddd, J = 8.4, 7.3,
1.4 Hz, 1H), 7.40 (td, J = 7.5, 0.9 Hz, 1H), 7.26 (t, J = 7.8 Hz, 1H), 7.04
(dd, J = 8.0, 1.1 Hz, 1H), 1.42 - 1.30 (m, 3H), 1.11 (s, 9H), 1.10 (s, 9H).
13C NMR (126 MHz, DMSO-d6) δ 155.2, 146.4, 140.9, 127.6, 125.5,
123.9, 123.8, 123.1, 121.3, 117.9, 113.8, 111.7, 17.7 (6C), 12.2 (3C).
HR-GC-MS (TOF MS+) calculated for C21H28O2Si [M+]: 340.1859, found
340.1823.
1-Bromo-3-chloro-dibenzofuran-4-ol (25)
1-Bromo-dibenzofuran-4-ol (22) (72.4 g, 98 %, 269 mmol, 1 equiv.) was
dissolved in anhydrous THF (2.00 l). Upon addition of NCS (37.8 g,
283 mmol, 1 equiv.) and 30 drops 1M HCl, the yellow solution was stirred
at room temperature for 22 h. After reaction control by TLC and 1H NMR,
another portion of NCS (4.32 g, 32.4 mmol, 0.12 equiv.) and 10 drops 1M
HCl were added. The reaction was allowed to stir at room temperature
for 22 h. The solvent was partially removed and the residue was diluted
with toluene and water. The aqueous layer was acidified with 1M HCl to
pH 2-3 and extracted with toluene. The combined organic layers were
washed with water three times and with brine once. Afterwards, the
organic layer was dried over anhydrous sodium sulfate, filtered and
concentrated to give a white-yellowish solid (86 g). The crude was
suspended in cyclohexane (600 ml) and stirred at 60°C for 30 min, then
at room temperature over night. The product was collected by filtration,
washed with cyclohexane and dried in vacuo at 50 °C to give a title
compound as a white solid (80.2 g, 94 %, 254 mmol, 94 % yield).
1H NMR (500 MHz, THF-d8) δ 9.75 (s, 1H), 8.44 (dd, J = 7.9, 1.3 Hz, 1H),
7.64 (d, J = 8.3 Hz, 1H), 7.54 (ddd, J = 8.5, 7.2, 1.3 Hz, 1H), 7.52 (s, 1H),
7.42 (td, J = 7.7, 1.0 Hz, 1H). 13C NMR (101 MHz, THF-d8) δ 157.6,
146.7, 140.5, 129.0, 128.2, 125.0, 124.7, 124.1, 123.3, 120.6, 112.5,
104.5. HR-GC-MS (TOF MS+) calculated for C12H6O2ClBr [M+]:
295.9240, found 295.9251. Melting point: 175 °C.
1-Bromo-dibenzofuran-4-ol (22)
(Dibenzofuran-4-yloxy)-triisopropyl-silane (21) (112 g, 91 %, 82.3 mmol,
1 equiv.) was dissolved in anhydrous THF (2.00 l). NBS (57.6 g,
323 mmol, 1.08 equiv.) was added at room temperature to the pale
yellow solution. The now yellow solution was allowed to stir at room
temperature for 17 h. After reaction control by TLC and 1H NMR, CsF
(113 g, 749 mmol, 2.5 equiv.) was added. After 19 h, the now purple
solution was diluted with toluene and water. The aqueous layer was
acidified with 1M HCl to pH 2-3 and extracted with toluene three times.
The organic layer was washed with water and brine, dried over
anhydrous sodium sulfate, filtered and concentrated. The crude product
(135 g white-yellowish solid with an unpleasant smell) was suspended in
cyclohexane (800 ml) and stirred at 60 °C for 30 min, then at room
temperature over night. The solid was collected by filtration and dried in
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201801286
European Journal of Organic Chemistry
FULL PAPER
Trifluoromethanesulfonic acid 1-bromo-dibenzofuran-4-yl ester (26)
The compound was prepared by following general procedure A, using
compound 22 (894 mg, 3.40 mmol, 1 equiv.), anhydrous DCM (35 ml),
NEt3 (1.42 ml, 10.2 mmol, 3 equiv.) and Tf2O (0.70 ml, 4.25 mmol,
1.25 equiv.). The crude received from the aqueous work-up was purified
by column chromatography (SiO2, Hep/EE 100:0  92:8) to give a
colorless oil that crystallized to a white solid after storage in the
refrigerator for one day (1.02 g, 2.58 mmol, 89 % yield). 1H NMR (500
MHz, DMSO-d6) δ 8.49 (dd, J = 8.2, 0.9 Hz, 1H), 7.92 (dt, J = 8.4, 0.8 Hz,
1H), 7.79 (d, J = 8.8 Hz, 1H), 7.73 (ddd, J = 8.5, 7.3, 1.4 Hz, 1H), 7.72 (d,
J = 8.8 Hz, 1H), 7.60 (ddd, J = 8.1, 7.4, 0.9 Hz, 1H). 13C NMR (126 MHz,
DMSO-d6) δ 155.8, 146.2, 132.7, 129.8, 127.8, 126.1, 124.4, 122.2,
122.1, 121.7, 118.2 (q, J = 321 Hz), 115.2, 112.4. 19F NMR (471 MHz,
DMSO-d6) δ -72.86. HR-GC-MS (TOF MS+) calculated for C13H6O4SF3Br
[M+]: 393.9122, found 393.9131. Melting point: 70 °C.
Compound 29 (33.2 g, 69.6 mmol, 1 equiv.), 2-chloro-4,6-biphenyl-
[1,3,5]-triazin (18.6 g, 69.6 mmol, 1 equiv.), Na2CO3 (18.5 g, 174 mmol,
2.5 equiv.) were dissolved in toluene (600 ml) and water (140 ml). The
mixture was saturated with argon for 1 h, followed by the addition of
Pd2dba3 (638 mg, 0.70 mmol, 1 mol-%) and P(o-Tol)3 (848 mg,
2.79 mmol, 4 mol-%). The solution was vigorously stirred at 90 °C for
17 h. After cooling to room temperature, the mixture was washed with
water three times. The organic layer was dried over anhydrous sodium
sulfate and concentrated to give a brown oil (47.9 g) that was dissolved
in cyclohexane (400 ml) at 60 °C. After stirring at room temperature over
night, the crystallized solid was collected by filtration, washed with
cyclohexane and dried in vacuo at 80 °C to yield the product as a beige
solid (34.1 g, 90 %, 52.7 mmol, 75 % yield). 1H NMR (500 MHz, THF-d8)
δ 8.85 - 8.78 (m, 4H), 8.64 (d, J = 8.1 Hz, 1H), 8.58 (s, 1H), 7.79 (d,
J = 8.3 Hz, 1H), 7.71 - 7.63 (m, 3H), 7.61 (t, J = 7.6 Hz, 4H), 7.32 (t,
J = 7.6 Hz, 1H). 13C NMR (126 MHz, THF-d8) δ 173.3 (2C), 172.4, 158.7,
149.7, 136.7 (2C), 134.6, 134.2 (2C), 133.8, 130.8, 130.2 (4C), 129.9
(4C), 128.5, 127.5, 126.7, 126.4, 124.8, 123.6, 119.9 (q, J = 321 Hz,
112.9. 19F NMR (471 MHz, THF-d8) δ -74.04. HR-GC-MS (TOF MS+)
calculated for C28H16ClF3N3O4S [M+]: 582.0497, found 582.0500.
Melting point: 157 °C.
Trifluoromethanesulfonic acid 3-bromo-dibenzofuran-4-yl ester (27)
The compound was prepared by following general procedure A using
compound 24 (2.00 g, 7.60 mmol, 1 equiv.), anhydrous DCM (45 ml),
NEt3 (3.16 ml, 22.8 mmol, 3 equiv.) and Tf2O (1.51 ml, 9.12 mmol,
1.2 equiv.). The crude received from the aqueous work-up was purified
by column chromatography (SiO2, Hep/EE 100:0  91:9) to give a pale
yellow oil that crystallized to a white solid after storage in the refrigerator
for 1h (2.39 g, 6.05 mmol, 80 % yield). 1H NMR (500 MHz, DMSO-d6) δ
8.27 (dd, J = 7.9, 1.3 Hz, 1H), 8.25 (d, J = 8.3 Hz, 1H), 7.87 (d, J = 8.3
Hz, 1H), 7.81 (d, J = 8.3 Hz, 1H), 7.66 (ddd, J = 8.4, 7.3, 1.3 Hz, 1H),
7.52 (td, J = 7.5, 0.9 Hz, 1H). 13C NMR (126 MHz, DMSO-d6) δ 155.9,
146.5, 131.2, 129.3, 128.3, 126.9, 124.5, 122.7, 122.3, 122.1, 118.1 (q,
J = 321 Hz), 113.9, 112.1. 19F NMR (471 MHz, DMSO-d6) δ -72.67.
HR-GC-MS (TOF MS+) calculated for C13H6O4F3SBr [M+]: 393.9122,
found 393.9127. Melting point: 76 °C.
2-(3-Chloro-dibenzofuran-1-yl)-4,6-diphenyl-[1,3,5]triazine (30)
Compound 30a (34 g, 90 %, 52.6 mmol, 1 equiv.) was dissolved in
anhydrous DMF (550 ml). The suspension was saturated with argon for
40 min. Then, Pd(OAc)2 (236 mg, 1.05 mmol, 2 mol-%) and dppp
(447 mg, 1.05 mmol, 2 mol-%) were added, followed by triethylsilane
(21 ml, 131 mmol, 2.5 equiv.). The suspension was stirred vigorously at
65 °C for 3.5 h. After cooling to room temperature, the precipitated solid
was collected by filtration, suspended in water and stirred for 30 min.
Afterwards, the solid was again collected by filtration, washed with water
and dried in vacuo at 55 °C over night to yield a pale beige solid (21.6 g,
92 %, 45.8 mmol, 87 % yield). 1H NMR (500 MHz, THF-d8) δ 8.85 - 8.77
(m, 4H), 8.62 (dd, J = 8.1, 1.2 Hz, 1H), 8.41 (d, J = 1.9 Hz, 1H), 7.97 (d,
J = 1.9 Hz, 1H), 7.69 - 7.64 (m, 3H), 7.60 (t, J = 7.4 Hz, 4H), 7.54 (ddd,
J = 8.3, 7.1, 1.3 Hz, 1H), 7.24 (t, J = 8.1 Hz, 1H). 13C NMR (126 MHz,
THF-d8) δ 173.4, 173.1 (2C), 158.5, 158.4, 137.0 (2C), 135.3, 134.0 (2C),
133.3, 130.2 (4C), 129.8 (4C), 129.6, 127.2, 127.1, 123.9, 123.8, 123.3,
115.9, 112.4. HR-GC-MS (TOF MS+) calculated for C27H16N3OCl [M+]:
433.0982, found 433.0993. Melting point: 250 °C.
Trifluoromethanesulfonic acid 1-bromo-3-chloro-dibenzofuran-4-yl
ester (28)
The compound was prepared by following general procedure A using
compound 25 (40 g, 94 %, 126 mmol, 1 equiv.), anhydrous DCM
(800 ml), NEt3 (52.7 ml, 380 mmol, 3 equiv.) and Tf2O (31.4 ml,
190 mmol, 1.5 equiv.). The crude received from the aqueous work-up
was filtered over silica gel (SiO2, Hep/THF 9:1) to give a yellow oil that
crystallized to a solid upon standing at air (46.5 g, 89 % accompanied by
THF, 96.4 mmol, 76 % yield). 1H NMR (500 MHz, DMSO-d6) δ 8.43 (dd,
J = 7.9, 1.6 Hz, 1H), 8.10 (d, J = 1.3 Hz, 1H), 7.87 (dt, J = 8.4, 0.9 Hz,
1H), 7.73 (ddt, J = 8.3, 7.3, 1.0 Hz, 1H), 7.59 (tt, J = 7.4, 0.9 Hz, 1H).
13C NMR (126 MHz, DMSO-d6) δ 156.1, 146.9, 130.0, 129.5, 128.0,
125.5, 125.4, 124.7, 122.1, 121.9, 118.0 (q, J = 321 Hz), 115.2, 112.3.
19F NMR (471 MHz, DMSO-d6) δ -72.68. HR-GC-MS (TOF MS+)
calculated for C13H5O4F3SClBr [M+]: 427.8733, found 427.8774. Melting
point: 92 °C.
Trifluoromethanesulfonic
dibenzofuran-1-yl ester (32)
acid
8-(9-phenyl-9H-carbazol-3-yl)-
The compound was prepared following general procedure D using
compound 5 (78 g, 195 mmol, 1 equiv.), boronic acid 31 (67.2 g,
234 mmol, 1.2 equiv.), K2CO3 (54.1 g, 391 mmol, 2 equiv.), toluene
(750 ml) and water (250 ml). The suspension was saturated with argon
for 30 min, followed by the addition of Pd2dba3 (892 mg, 0.97 mmol,
0.5 mol-%) and P(o-Tol)3 (1.18 g, 3.90 mmol, 2 mol-%). The mixture was
stirred at 85 °C for 20 h. After cooling to room temperature, layers were
separated and the organic layer was washed with water three times, then
dried over anhydrous sodium sulfate, filtered and concentrated to
approximately 1 l. The crystallized product was collected by filtration,
washed with toluene and dried in vacuo at 60 °C to afford the title
compound as a white solid (85.1 g, 153 mmol, 78 % yield). 1H NMR
(500 MHz, DMSO-d6) δ 8.59 (d, J = 2.0 Hz, 1H), 8.36 - 8.30 (m, 2H), 8.08
(dd, J = 8.6, 2.0 Hz, 1H), 7.96 (d, J = 7.5 Hz, 1H), 7.94 (d, J = 7.1 Hz, 1H),
7.76 (dd, J = 8.5, 1.9 Hz, 1H), 7.75 (d, J = 8.3 Hz, 1H), 7.75 - 7.68 (m,
2H), 7.70 - 7.64 (m, 2H), 7.61 - 7.53 (m, 1H), 7.55 (d, J = 8.2 Hz, 1H),
7.51 (d, J = 8.5 Hz, 1H), 7.48 (ddd, J = 8.3, 7.0, 1.3 Hz, 1H), 7.41 (d,
J = 8.2 Hz, 1H), 7.34 (td, J = 7.5, 1.1 Hz, 1H). 13C NMR (126 MHz,
DMSO-d6) δ 157.0, 154.7, 142.6, 140.7, 139.7, 137.3, 136.7, 132.0,
130.2 (2C), 128.9, 128.3, 127.7, 126.6 (2C), 126.5, 125.3, 123.5, 122.7,
120.6, 120.5, 120.2, 119.6, 118.7, 118.1 (q, J = 321 Hz), 116.9, 115.8,
112.8, 112.6, 110.3, 109.8. 19F NMR (471 MHz, DMSO-d6) δ -73.08.
HR-LC-MS (LC-APLI-MS) calculated for C31H19F3NO4S [M+H+]:
558.0981, found 558.0994. Melting point: 161 °C.
Trifluoromethanesulfonic
acid
3-chloro-1-(4,4,5,5-tetra-methyl-
[1,3,2]dioxaborolan-2-yl)-dibenzofuran-4-yl ester (29)
The compound was prepared by following general procedure C using
compound 28 (46.5 g, 89 %, 96.4 mmol, 1 equiv.), B2pin2 (29.4 g,
116 mmol, 1.2 equiv.), KOAc (23.6 g, 241 mmol, 2.5 equiv.), anhydrous
toluene (1.00 l) and Pd(dppf)Cl2 (705 mg, 0.96 mmol, 1 mol-%). After
21 h and reaction control by 1H NMR, another portion of catalyst (705 mg,
0.96 mmol, 1 mol-%) was added and the mixture was stirred at 85 °C for
another 72 h. The crude (57 g) was suspended in cyclohexane (400 ml)
and stirred at 60 °C for 1 h, then at room temperature over night. The
product was collected by filtration and dried in vacuo at 50 °C to yield a
beige solid (33.4 g, 70.0 mmol, 72 % yield). 1H NMR (500 MHz, THF-d8)
δ 8.94 (d, J = 8.3 Hz, 1H), 7.97 (s, 1H), 7.69 (dt, J = 8.4, 0.8 Hz, 1H),
7.58 (ddd, J = 8.4, 7.2, 1.4 Hz, 1H), 7.43 (ddd, J = 8.1, 7.2, 1.0 Hz, 1H),
1.47 (s, 12H). 13C NMR (126 MHz, THF-d8) δ 158.4, 148.6, 133.7, 133.5,
132.1, 130.0, 126.3, 125.6, 124.9, 124.8, 119.9 (q, J = 321 Hz), 112.6,
86.1 (2C), 25.3 (4C). 19F NMR (471 MHz, THF-d8) δ -74.19. HR-GC-MS
(TOF MS+) calculated for C19H17O6SClF3B [M+]: 476.0480, found
476.0513. Melting point: 163 °C.
3-(8-Bromo-dibenzofuran-1-yl)-9-phenyl-9H-carbazole (33)
The compound was prepared by following general procedure E except
that Na2CO3 was replaced with K2CO3. The mixture was purified by
column chromatography (SiO2, heptane / ethyl acetate 95:5  85:15) to
yield a white solid (249 mg, 0.51 mmol, 85 % yield). 1H NMR (700 MHz,
2-(3-Chloro-dibenzofuran-1-yl)-4,6-diphenyl-[1,3,5]triazine (30)
Trifluoromethanesulfonic acid 3-chloro-1-(4,6-diphenyl-[1,3,5]triazin-2-yl)-
dibenzofuran-4-yl ester (30a)
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201801286
European Journal of Organic Chemistry
FULL PAPER
THF-d8) δ 8.45 (d, J = 1.6 Hz, 1H), 8.22 (d, J = 7.7 Hz, 1H), 7.79 (d,
J = 1.6 Hz, 1H), 7.71 (dd, J = 7.5, 6.2 Hz, 2H), 7.70 - 7.67 (m, 3H),
7.62 - 7.60 (m, 2H), 7.59 (d, J = 8.2 Hz, 1H), 7.57 - 7.54 (m, 2H), 7.53 (m,
1H), 7.46 (d, J = 8.2 Hz, 1H), 7.43 (m, 1H), 7.41 (dd, J = 6.8, 1.5 Hz, 1H),
7.28 (t, J = 7.3 Hz, 1H). 13C NMR (176 MHz, THF-d8) δ 158.3, 156.3,
142.6, 141.8, 140.3, 138.8, 132.3, 131.1 (2C), 130.9, 129.1, 128.7, 128.1
(2C), 127.8, 127.3, 126.0, 125.9, 125.1 (2C), 124.6, 121.8, 121.6, 121.3,
121.3, 116.0, 114.1, 111.0, 110.9, 110.8. HR-GC-MS (TOF MS EI+)
calculated for C30H18NOBr [M+]: 487.0572, found 487.0566. Melting
point: 151 °C.
130.9, 128.8, 128.7, 128.1 (2C), 127.9, 127.3, 126.8, 125.2, 124.9, 124.5,
124.4, 123.9, 123.6, 121.6, 121.4, 121.3, 112.7, 110.9, 110.8, 103.6.
HR-GC-MS (TOF MS+) calculated for C30H18NOBr [M+]: 487.0572, found
487.0517. Melting point: 176 °C.
3-(1-Bromo-dibenzofuran-4-yl)-9-phenyl-9H-carbazole (46)
The compound was prepared by following general procedure E and
purified by column chromatography (SiO2, Hep/THF 99:1  80:20) to
give a white solid (258 mg, 0.53 mmol, 85 %). 1H NMR (700 MHz,
THF-d8) δ 8.71 (d, J = 1.4 Hz, 1H), 8.58 (d, J = 7.9 Hz, 1H), 8.26 (d,
J = 7.7 Hz, 1H), 7.96 (dd, J = 8.5, 1.8 Hz, 1H), 7.69 (d, J = 8.2 Hz, 2H),
7.68 - 7.66 (m, 4H), 7.66 (d, J = 8.0 Hz, 1H), 7.56 (td, J = 8.3, 1.2 Hz, 1H),
7.53 (d, J = 8.5 Hz, 1H), 7.52 - 7.50 (m, 1H), 7.44 (t, J = 7.3 Hz, 1H),
7.43 - 7.39 (m, 2H), 7.28 (ddd, J = 7.8, 6.4, 1.4 Hz, 1H).13C NMR
(176 MHz, THF-d8) δ 157.4, 154.9, 142.5, 141.8, 138.8, 131.0 (2C),
129.0, 128.9, 128.7, 128.6 (2C), 128.2, 128.1 (2C), 127.9, 127.2, 125.2,
125.0, 124.9, 124.7, 123.8, 123.5, 121.6, 121.4, 121.2, 114.6, 112.6,
110.8, 110.8. HR-GC-MS (TOF MS+) calculated for C30H18NOBr [M+]:
487.0572, found 487.0587. Melting point: 170 °C.
Trifluoromethanesulfonic
dibenzofuran-1-yl ester (34)
acid
2-(9-phenyl-9H-carbazol-3-yl)-
The compound was prepared by following general procedure D and
purified by column chromatography (SiO2, heptane / ethyl acetate
99:1  90:10) to yield a white solid (160 mg, 0.28 mmol, 48 %). 1H NMR
(500 MHz, THF-d8) δ 8.42 (d, J = 1.7 Hz, 1H), 8.33 (d, J = 7.7 Hz, 1H),
8.23 (d, J = 7.7 Hz, 1H), 7.83 (d, J = 8.4 Hz, 1H), 7.78 (d, J = 8.5 Hz, 1H),
7.71 (d, J = 8.3 Hz, 1H), 7.70 - 7.65 (m, 4H), 7.65 - 7.59 (m, 2H), 7.52 (d,
J = 8.4 Hz, 1H), 7.52 - 7.48 (m, 1H), 7.48 (t, J = 7.5 Hz, 1H), 7.46 - 7.42
(m, 1H), 7.40 (dd, J = 8.3, 1.2 Hz, 1H), 7.28 (ddd, J = 8.0, 6.5, 1.6 Hz,
1H). 13C NMR (101 MHz, THF-d8) δ 157.8, 157.3, 142.6, 141.7, 141.0,
138.8, 132.8, 132.3, 131.1 (2C), 129.6, 128.8, 128.7, 128.1 (2C), 127.3,
125.0, 124.6, 124.5, 123.9, 122.9, 122.4, 121.4, 121.3, 120.8, 120.3,
119.3 (q, J = 321 Hz), 113.2, 112.8, 110.9, 110.7. 19F NMR (471 MHz,
THF-d8) δ -75.24. HR-LC-MS (LC-APLI-MS) calculated for C31H19F3NO4S
[M+H+]: 558.0981, found 558.0979. Melting point: 184 °C.
Acknowledgements
We thank Philipp Fackler for support regarding compound 5 and
supply regarding compound 1 and the analytics department of
Merck KGaA for analytical support.
Trifluoromethanesulfonic
dibenzofuran-1-yl ester (35)
acid
4-(9-phenyl-9H-carbazol-3-yl)-
The compound was prepared by following general procedure D and
purified by column chromatography (SiO2, heptane / THF 98:2  85:15)
to yield a white solid (100 mg, 0.18 mmol, 30 % yield). 1H NMR (700 MHz,
THF-d8) δ 8.73 (d, J = 1.8 Hz, 1H), 8.26 (d, J = 7.7 Hz, 1H), 8.22 (dd,
J = 7.7, 1.1 Hz, 1H), 7.98 (dd, J = 8.4, 1.8 Hz, 1H), 7.88 (d, J = 8.4 Hz,
1H), 7.75 (d, J = 8.2 Hz, 1H), 7.71 - 7.65 (m, 4H), 7.61 (dd, J = 8.1,
1.3 Hz, 1H), 7.56 (d, J = 8.6 Hz, 1H), 7.54 (d, J = 8.3 Hz, 1H), 7.53 (m,
1H), 7.50 (t, J = 7.5 Hz, 1H), 7.45 - 7.40 (m, 2H), 7.30 (ddd, J = 7.9, 6.1,
1.8 Hz, 1H). 13C NMR (176 MHz, THF-d8) δ 157.4, 155.3, 143.3, 142.6,
141.9, 138.8, 131.1 (2C), 129.7, 128.7, 128.7, 128.6, 128.1 (2C), 127.9,
127.9, 127.3, 125.0, 124.8, 124.6, 123.4, 122.1, 121.9, 121.4, 121.3,
120.0 (q, J = 321 Hz), 119.1, 116.8, 113.1, 110.9. 19F NMR (471 MHz,
THF-d8) δ -74.51. HR-GC-MS (TOF MS+) calculated for C31H18NO4F3S
[M+]: 557.0909, found 557.0903. Melting point: 157 °C.
Keywords: Dibenzofuran • Chemoselectivity • Cross-coupling •
Regioselectivity • Synthetic methods
[1]
a) Y. Feng, A. R. Carroll, R. Addepalli, G. A. Fechner, V. M. Avery, R.
Quinn, J. Nat. Prod. 2007, 70, 1790–1792. b) J.-J. Chen, Y.-T. Luo,
C.-H. Liao, I.-S. C. Chen, C.-C. Liaw, Chem. Biodivers. 2009, 6,
774-778. c) M. N. A. Khalil, W. Brandt, T. Beuerle, D. Reckwell, J.
Groeneveld, R. Hänsch, M. M. Gaid, B. Liu, L. Beerhues, Plant J. 2015,
83, 263–276. d) Y. Q. Ye, H. Koshino, J. I. Onose, K. Yoshikawa, N.
Abe, S. Takahashi, Org. Lett. 2009, 11, 5074–5077.
[2]
a) S. Prado, Y. L. Janin, B. Saint-Joanis, P. Brodin, S. Michel, M. Koch,
S. T. Cole, F. Tillequin, P. E. Bost, Bioorg. Med. Chem. 2007, 15,
2177-2186. b) B. E. Love, Eur. J. Med. Chem. 2015, 97, 377-387. c) S.
Masaki, I. Kii, Y. Sumida, T. Kato-Sumida, Y. Ogawa, N. Ito, M.
Nakamura, R. Sonamoto, N. Kataoka, T. Hosoya, M. Hagiwara, Bioorg.
Med. Chem. 2015, 23, 4434-4441. d) K. Y. Tsang, H. Diaz, N. Graciani,
J. W. Kelly, J. Am. Chem. Soc. 1994, 116, 3988-4005. e) B. Voigt, L.
Meijer, O. Lozach, C. Schächtele, F. Totzke, A. Hilgeroth, Bioorg. Med.
Chem. Lett. 2005, 15, 823-825. f) A. M. Oliveira, M. M. Raposo, A. M.
Oliveira-Campos, A. E. Machado, P. Puapairoj, M. Pedro, M. S.
Nascimento, C. Portela, C. Afonso, M. Pinto, Eur. J. Med. Chem. 2006,
41, 367–372.
3-(2-Bromo-dibenzofuran-1-yl)-9-phenyl-9H-carbazole (43)
The compound was prepared by following general procedure E except
that Na2CO3 was replaced with K2CO3. The mixture was purified by
column chromatography (SiO2, heptane / ethyl acetate 100:0  92:8) to
yield a white solid (212 mg, 0.43 mmol, 72 % yield). 1H NMR (700 MHz,
THF-d8) δ 8.24 (d, J = 2.0 Hz, 1H), 8.16 (d, J = 7.7 Hz, 1H), 7.82 (d,
J = 8.7 Hz, 1H), 7.74 (dd, J = 8.1, 1.3 Hz, 2H), 7.69 (t, J = 7.8 Hz, 2H),
7.62 (d, J = 8.3 Hz, 1H), 7.57 (d, J = 8.7 Hz, 1H), 7.56 (d, J = 8.2 Hz, 1H),
7.53 (t, J = 7.4 Hz, 1H), 7.48 (d, J = 8.4 Hz, 1H), 7.44 (dd, J = 8.4, 1.8 Hz,
1H), 7.43 - 7.40 (m, 1H), 7.36 (td, J = 7.2, 1.4 Hz, 1H), 7.25 (t, J = 7.4 Hz,
1H), 6.96 (t, J = 7.6 Hz, 1H), 6.81 (dd, J = 8.0, 1.2 Hz, 1H). 13C NMR
(176 MHz, THF-d8) δ 157.9, 156.2, 142.5, 141.7, 139.3, 138.8, 131.9,
131.6, 131.0 (2C), 128.6, 128.5, 128.2 (2C), 128.1, 127.3, 126.2, 124.9,
124.9, 124.6, 123.7, 123.3, 122.2, 121.5, 121.2, 118.9, 112.9, 112.4,
111.0, 110.8. HR-GC-MS (TOF MS+) calculated for C30H18NOBr [M+]:
487.0572, found 487.0560. Melting point: 136 °C.
[3]
[4]
H. Lusic, R. Uprety, A. Deiters, Org. Lett. 2010, 12, 916–919.
a) Y. Im, J. Y. Lee, Dyes Pigm. 2015, 113, 743-747. b) J. G. Yu, S. Y.
Byeon, S. H. Han, J. Y. Lee, Chem. - Eur. J. 2017, 23, 16044-16050.
c) Y. Im, J. Y. Lee, Dyes Pigm. 2016, 128, 84–88.
[5]
P. Camargo Solórzano, F. Brigante, A. B. Pierini, L. B. Jimenez, J. Org.
Chem. 2018, 83, 7867-7877.
[6]
[7]
N. Panda, I. Mattan, D. K. Nayak, J. Org. Chem. 2015, 80, 6590-6597.
a) H. Gilman, L. C. Cheney, H. B. Willis, J. Am. Chem. Soc. 1939, 61,
951-954. b) H. Gilman, M. W. V. Ess, D. M. Hayes, J. Am. Chem. Soc.
1939, 61, 643-648. c) H. Gilman, G. E. Brown, W. G. Bywater, W. H.
Kirkpatrick, J. Am. Chem. Soc. 1934, 56, 2473-2477.
3-(4-Bromo-dibenzofuran-1-yl)-9-phenyl-9H-carbazole (44)
The compound was prepared by following general procedure E and
purified by column chromatography (heptane/THF 95:5  85:15) to yield
a white solid (234 mg, 0.48 mmol, 80 % yield). 1H NMR (700 MHz,
THF-d8) δ 8.44 (d, J = 1.7 Hz, 1H), 8.19 (d, J = 7.6 Hz, 1H), 7.74 (d,
J = 8.0 Hz, 1H), 7.72 - 7.69 (m, 2H), 7.68 (d, J = 8.1 Hz, 3H), 7.67 (dd,
J = 8.3, 1.8 Hz, 1H), 7.58 (d, J = 8.4 Hz, 2H), 7.53 (tt, J = 6.4, 2.0 Hz, 1H),
7.48 - 7.44 (m, 2H), 7.44 - 7.40 (m, 1H), 7.31 (d, J = 8.0 Hz, 1H), 7.27 (td,
J = 7.9, 1.1 Hz, 1H), 7.11 (t, J = 7.6 Hz, 1H). 13C NMR (176 MHz,
THF-d8) δ 157.4, 154.5, 142.6, 141.8, 139.4, 138.8, 131.9, 131.1 (2C),
[8]
[9]
H. Gilman, P. R. Van Ess, J. Am. Chem. Soc. 1939, 61, 1365-1371.
a) K. Oita, R. G. Johnson, H. Gilman, J. Org. Chem. 1955, 20, 657-667.
b) H. Gilman, D. L. Esmay, J. Am. Chem. Soc. 1954, 76, 5787-5788.
[10] Y. Feng, J. Xueyi, L. Yao, Organic Compound and Application Thereof
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201801286
European Journal of Organic Chemistry
FULL PAPER
to Organic Electroluminescent Devices, Beijing Green Guardee Tech
Co Ltd, February 15, 2017, CN106397398.
Szymanski, B. L. Feringa, Angew. Chem. Int. Ed. 2017, 56, 3354-3359.
[36] D. Heijnen, J. B. Gualtierotti, V. Hornillos, B. L. Feringa, Chem. - Eur. J.
2016, 22, 3991-3995.
[11] T. Oh-E, N. Miyaura, A. Suzuki, Synlett 1990, 221-223.
[12] I. Beetz, I. Schumann, A. Huth, Tetrahedron 1989, 45, 6679-6682.
[13] J. m. Fu, V. Snieckus, Tetrahedron Lett. 1990, 31, 1665-1668.
[14] T. Oh-E, N. Miyaura, A. Suzuki, J. Org. Chem. 1993, 58, 2201-2208.
[15] G. Espino, A. Kurbangalieva, J. M. Brown, Chem. Commun. 2007,
1742-1744.
[37] F. Du, Q. Zhou, D. Liu, T. Fang, Y. Shi, Y. Du, G. Chen, X. R. Br,
Synlett 2018, 29, 779–784.
[16] T. Kamikawa, T. Hayashi, Tetrahedron Lett. 1997, 38, 7087-7090.
[17] T. Ooi, M. Kameda, K. Maruoka, J. Am. Chem. Soc. 2003, 125,
5139-5151.
[18] A. F. Littke, C. Dai, G. C. Fu, J. Am. Chem. Soc. 2000, 122, 4020-4028.
[19] Y. Y. Ku, T. Grieme, Y. M. Pu, A. V. Bhatia, Adv. Synth. Catal. 2009,
351, 2024-2030.
[20] Z. Khaddour, N. Eleya, O. A. Akrawi, A. M. Hamdy, T. Patonay, A.
Villinger, P. Langer, Tetrahedron Lett. 2013, 54, 5201-5203.
[21] a) Z. Khaddour, N. Eleya, O. A. Akrawi, A. M. Hamdy, T. Patonay, A.
Villinger, P. Langer, Synlett 2013, 24, 2114-2118. b) Z. Hassan, S. Al-
Shidhani, A. Al-Ghafri, A. Al-Harrasi, J. Hussain, R. Csuk, Tetrahedron
Lett. 2015, 56, 7141-7144. c) D. Pajtás, K. Dihen, K. Kónya, P. Langer,
Synlett 2016, 27, 1073-1076. d) A. M. Hamdy, N. Eleya, H. H.
Mohammed, T. Patonay, A. Spannenberg, P. Langer, Tetrahedron
2013, 69, 2081-2086. e) D. Patjas, K. Dihen, T. Patonay, A. Villinger, P.
Langer, Synlett 2015, 26, 2601-2605. f) S. T. Handy, Y. Zhang, Chem.
Commun. 2006, 299-301. g) S. Jordán, D. Pajtás, T. Patonay, P.
Langer, K. Kónya, Synthesis 2017, 49, 1983-1992. h) N. Eleya, Z.
Khaddour, T. Patonay, P. Langer, Synlett 2012, 223-226. i) T. Q. Hung,
T. T. Dang, J. Janke, A. Villinger, P. Langer, Org. Biomol. Chem. 2015,
13, 1375-1386.
[22] T. Kamikawa, T. Hayashi, J. Org. Chem. 1998, 63, 8922-8925.
[23] S. Zhong, Y. Zhou, X. Feng, M. Wu, F. Meng, D. Sun, A Preparing
Method of a Dibenzofuran Compound, CECEP Valiant Co., Ltd., Peop.
Rep. China, February 02, 2016, CN 105348240.
[24] J. V. Greenhill, M. A. Moten, R. Hanke, J. Chem. Soc., Perkin Trans. 1
1984, 1213-1217.
[25] S. Gupta, P. Chaudhary, V. Srivastava, J. Kandasamy, Tetrahedron
Lett. 2016, 57, 2506-2510.
[26] J. M. Herbert, A. D. Kohler, F. Le Strat, D. Whitehead, J. Labelled
Compd. Radiopharm. 2007, 50, 440-441.
[27] a) B. M. Trost, O. R. Thiel, H.-C. Tsui, J. Am. Chem. Soc. 2003, 125,
13155-13164. b) J. B. McManus, D. A. Nicewicz, J. Am. Chem. Soc.
2017, 139, 2880-2883.
[28] a) G. Cherry, J.-C. Culmann, J. Sommer, Tetrahedron Lett. 2007, 31,
2007-2010. b) J. M. Brittain, P. B. D. de la Mare, P. A. Newman,
Tetrahedron Lett. 1980, 21, 4111-4112.
[29] a) H. Kotsuki, P. K. Datta, H. Hayakawa, H. Suenaga, Synthesis 1995,
1348-1350. b) Q.-Y. Chen, Y.-B. He, Z.-Y. Yang, J. Chem. Soc., Chem.
Commun. 1986, 1452-1453. c) X. Y. Wang, J. Leng, S. M. Wang, A. M.
Asiri, H. M. Marwani, H. L. Qin, Tetrahedron Lett. 2017, 58, 2340-2343.
[30] a) J. F. Hartwig, F. Paul, J. Am. Chem. Soc. 1995, 117, 5373-5374.
b) F. Paul, J. Patt, J. F. Hartwig, Organometallics 1995, 14, 3030-3039.
c) F. Paul, J. Patt, J. F. Hartwig, J. Am. Chem. Soc. 1994, 116,
5969-5970.
[31] A. Jutand, A. Mosleh, Organometallics 1995, 14, 1810-1817.
[32] G. R. Fulmer, A. J. M. Miller, N. H. Sherden, H. E. Gottlieb, A.
Nudelman, B. M. Stoltz, J. E. Bercaw, K. I. Goldberg, Organometallics
2010, 29, 2176-2179.
[33] a) R. L. Hansen, Perfluoraloalkane Sulfonate Esters, 3M Co, Minnesota
Mining and MFG, October 10, 1967, US3346612A. b) I. Kalvet, G.
Magnin, F. Schoenebeck, Angew. Chem., Int. Ed. 2017, 56, 1581-1585.
[34] H. Ogawa, K. Kondo, T. Shinohara, K. Kan, Y. Tanada, M. Kurimura, S.
Mortia, M. Uchida, T. Mori, M. Tominaga, Y. Yabuuchi,
Benzoheterocyclic Derivatives, Otsuka Pharmaceutical Co, June
26, 1997, WO9722591.
[35] D. Heijnen, F. Tosi, C. Vila, M. C. A. Stuart, P. H. Elsinga, W.
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Entry for the Table of Contents
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Dibenzofuran Functionalization
Two dibenzofuranol starting materials
allowed for the synthesis of a variety
of bi- and tri-functionalized dibenzo-
furans with ten different substitution
patterns. For intermediates containing
both a bromine and a triflate moiety,
we describe a bromine or triflate-
C. Wern, C. Ehrenreich, D. Joosten, T.
vom Stein, H. Buchholz, B. König*
Page 1 – 12
Rapid Access to bi- and tri-
functionalized Dibenzofurans and
their Application in selective Suzuki-
Miyaura Cross Coupling Reactions
selective
mono-substitution
by
Suzuki-Miyaura reaction.
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