Ring Closing Metathesis Approach for the Synthesis of o-Terphenyl Derivatives

Article abstract of DOI:10.1002/ejoc.201900988

A linear synthesis of o-terphenyl derivatives has been delineated using ring closing metathesis (RCM) as the key step. In this approach, benzil derivatives upon allyl Grignard addition provides diphenyl-1,2-diallyl dihydroxy derivatives which undergo ring closing metathesis to afford tetrahydro terphenyl derivatives. Aromatization-driven dehydration then leads to a diverse set of electron rich and electron deficient o-terphenyls. Furthermore, oxidative coupling of electron rich o-terphenyls provides the corresponding triphenylene derivatives.

Full text of DOI:10.1002/ejoc.201900988

A Journal of
Accepted Article
Title: Ring Closing Metathesis Approach for the Synthesis of o-
Terphenyl Derivatives
Authors: Shilpi Karmakar, Tirtha Mandal, and Jyotirmayee Dash
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10.1002/ejoc.201900988
European Journal of Organic Chemistry
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Ring Closing Metathesis Approach for the Synthesis of o-
Terphenyl Derivatives
Shilpi Karmakar,[a] Tirtha Mandal[a] and Jyotirmayee Dash*[a]
Dedication ((optional))
Abstract: A linear synthesis of o-terphenyls derivatives has been
delineated using ring closing metathesis (RCM) as the key step. In
this approach, benzil derivatives upon allyl Grignard addition
provides diphenyl-1,2-diallyl dihydroxy derivatives which undergo
ring closing metathesis to afford tetrahydro terphenyl derivatives.
Aromatization-driven dehydration then leads to a diverse set of
electron rich and electron deficient o-terphenyls. Furthermore,
oxidative coupling of electron rich o-terphenyls provides the
corresponding triphenylene derivatives.
Introduction
Polycyclic aromatic hydrocarbons (PAHs)1 are a ubiquitous
group of several hundred chemically related compounds having
two or more single or fused aromatic rings. Terphenyls and
triphenylene systems are important PAHs owing to their
structural diversity and wide applications in various fields such
as supramolecular and organic material chemistry.2-5 Terphenyls
serves as leading components in organic and optoelectronic
devices. They are often exploited for designing organic
electroluminescent devices and liquid crystalline materials.4
Synthetic terphenyls also show significant biological activities
Scheme 1. Reported methods and our strategy for the synthesis of o-
like immunosuppressant, neuroprotective, antithrombotic,
anticoagulant, specific 5-lipoxygenase inhibitory and cytotoxic
activities.3
terphenyls and triphenylene derivatives.
Our interest is to develop an alternate and convenient protocol
for the synthesis of o-terphenyls from readily available starting
materials by using ring closing metathesis as the key step.
Several methods have been developed for the synthesis of
o-terphenyls.6 A rational route for the synthesis of substituted o-
terphenyl intermediate is palladium catalyzed cross-coupling
(Suzuki-Miyaura) reactions involving aryl boronic acids (Scheme
1, a). Considerable efforts have been made for the synthesis of
functionalized Pd ligands in order to carry out the reaction under
mild conditions as well as to improve the yield of o-terphenyls.
Gu et al. synthesized symmetrical o-terphenyls by developing
acid-based ligand.6i Lu et al. developed preligand for facile
synthesis of sterically hindered o-terphenyls.6k Miguez et al.
designed synthesis of unsymmetrical o-terphenyls at room
temperature using ligandless palladium catalyst.6a Besides Pd
catalysis, other routes have been developed for the synthesis of
Results and Discussion
Olefin metathesis based approaches have received
considerable attention for creating aromatic and heteroaromatic
compounds.7-10 In continuation of our work on RCM based
approaches for the synthesis of biologically significant
compounds,9,10 we herein disclose the synthesis of o-terphenyl
scaffolds using ring closing metathesis8 (RCM) as the key step.
We have synthesized both symmetrical and unsymmetrical o-
o-terphenyls;6
for
instance,
synthesis
involving
6π
terphenyls
using
1,2-diphenylethane-1,2-dione
(benzil)
electrocyclization of cis-triene intermediate, developed by Lim et
al. (Scheme 1, b).6f
derivatives11 as our synthetic precursors. In our approach,
triphenylenes 1 could be obtained via C-C coupling12 of o-
terphenyls 2, which could be acquired by dehydration of RCM
products 3. The allyl metal addition (Grignard reaction)13 of
benzils 5 could provide the diallylated products 4 as RCM
precursors for constructing the tricyclic diols 3.
[a]
S. Karmakar, T. Mandal, Prof. Dr. J. Dash
School of Chemical Sciences
Indian Association for the Cultivation of Science
Jadavpur, Kolkata-700032, India
email: ocjd@iacs.res.in
http://iacs.res.in/faculty-profile.html?id=98#
As benzil derivatives 5b-i are not commercially available,
they were prepared from the corresponding aromatic aldehydes
using previously reported procedures (Scheme 2). Symmetrical
benzil derivatives 5b-g were prepared from the corresponding
Supporting information for this article is given via a link at the end of
the document.
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aromatic aldehydes by pinacol coupling followed by Dess-Martin
periodinane (DMP) mediated oxidation.14 Unsymmetrical benzils
5h-i were prepared from corresponding acid chlorides by
phenylacetylene addition forming alkynone intermediates
followed by cleavage of the C-C bond using molecular
oxygen.11g,15
room temperature providing diallylated compound 4a in 60%
yield. The reaction of allylzinc bromide with benzil 5a provided
exclusively monoallyl compound 6a. Compound 6a further
reacted with allyl Grignard reagent to obtain the diallyl
compound 4a. We then explored the generality of the reaction
by allyl Grignard addition to electron rich and electron deficient
benzils. Symmetrical benzil derivatives 5a-g afforded the
corresponding symmetrical diallylated diols 4a-g in 55-70% yield
whereas the unsymmetrical benzils 5h-i produced the
corresponding unsymmetrical diallylated products 4h-i in 52-
60% yield (Table 1). The diol 4j containing a substituted allyl
group was synthesized from benzil 5a by sequential allyl indium
and Grignard reactions. First, 2-methylallyl group was
incorporated using indium-mediated allylation with 2-methylallyl
bromide to obtain homoallylic alcohol 6b, which was treated with
allyl Grignard reagent to give diol 4j (Scheme 3).
Scheme 2. Synthesis of symmetrical and unsymmetrical benzil derivatives.
Table 1. Synthesis of bisallylated diol derivatives[a]
Scheme 3. Allyl metal addition to benzil 5a.
Table 2. Ring closing metathesis (RCM) of the dialkene precursors[a]
[a]The addition of allylmagnesium halide (3.0 equiv, 1 M in THF) to 5a-i (2.0
mmol, 1.0 equiv) was carried out in THF (10 mL) at 0 °C and stirred at rt for 6
h.
[a]The reactions were performed using 4a-i (0.3 mmol, 1.0 equiv) with G-II
catalyst (5 mol %) in CH2Cl2 (8 mL) at rt for 15 h. [b]The reaction was
performed using 4j (0.3 mmol, 1.0 equiv) with G-II catalyst (5 mol %) in CH2Cl2
(8 mL) at 50 °C for 3 h.
To examine the feasibility of our approach (Scheme 1),
benzil 5a was treated with allylmagnesium bromide in THF at
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Using the synthesized bis-allylated diol precursors 4, the ring
closing metathesis (RCM) was next explored. In this step, 1,2-
diallyl derivatives 4a-j were subjected to RCM with Grubbs’
catalyst in dry CH2Cl2 to obtain the desired tricyclic diols 3a-j in
excellent yields (Table 3). RCM of the dialkene 4a with 10 mol%
of Grubbs’ first-generation catalyst (G-I)15 in dry CH2Cl2 at room
temperature provided the desired tetrahydro terphenyl derivative
3a in 78% yield, after separation by column chromatography.
Treating 4b with 10 mol% G-I provided 3b in poor yield.
However, the yield was improved by employing 5 mol% Grubbs’
second-generation catalyst (G-II)16. Thus, RCM of 4b-i was
performed with 5 mol% G-II providing 3b-i in high to excellent
yields (Table 2). Again, treating 4j with 5 mol% G-II at room
temperature provided 3j with poor yield. However, the yield
could be improved by carrying out the reaction at 50 °C for 3 h.
electron rich o-terphenyls containing methoxy group (s) 2f and 2i
underwent cyclization to form triphenylene derivatives 1f and 1i
whereas the electron deficient and unsubstituted o-terphenyls
remained inert under the reaction conditions (Table 4).
Table 4. Synthesis of triphenylene derivatives from o-terphenyls[a]
Next, we synthesized the corresponding o-terphenyls 2 by
dehydration of the RCM products 3 (Table 3). We observed that
dehydration of tetrahydro terphenyl derivative 3a using 30 mol%
p-toluenesulfonic acid (PTSA) in benzene at 80 °C for 3 h
provided o-terphenyl 2a in 77% yield. Subsequently, p-
toluenesulfonic acid (PTSA) assisted dehydration of tricyclic
diols 3b-j under similar reaction conditions led to aromatization,
providing the desired o-terphenyls 2b-j in excellent yields.
[a]The reactions were performed using 2f, 2i (0.3 mmol, 1.0 equiv.) in CH2Cl2 (8
mL) and FeCl3 (10.0 equiv.) in CH3NO2 (120 μL) at rt for 24 h.
Conclusions
In conclusion, the synthesis of o-terphenyls has been
delineated from easily accessible starting materials using simple
organic transformations. Allyl Grignard addition to substituted
benzil derivatives provides diallylated benzil derivatives suitable
for RCM. RCM has been employed effectively for the synthesis
tricyclic skeleton of the o-terphenyls. Aromatization driven
dehydration of the RCM products enable the synthesis of
desired symmetrical and unsymmetrical o-terphenyls containing
electron rich and electron deficient groups. Moreover, electron
rich o-terphenyls have been used to obtain triphenylene
derivatives via oxidative cyclization. The scope of this method
with the aim of evaluating its application for the synthesis of
diverse aromatic and heteroaromtic framework is currently under
study.
Table 3. Aromatization driven dehydration of the tricyclic diol compounds[a]
Experimental Section
All experiments were carried out in flame-dried reaction vials.
Solvents were dried using standard procedures. All starting
materials were obtained from commercial suppliers and used as
received. Products were purified by flash chromatography on
silica gel (100-200 mesh). Unless otherwise stated, yield refers
to analytical pure samples. Melting point is measured using
melting point apparatus. IR spectra were recorded using FT-IR
1
Spectrometer. NMR spectra were recorded in CDCl3. H NMR
spectra were recorded using 500 MHz and 400 MHz instruments
at 278 K. Signals are quoted as δ values in ppm using residual
protonated solvent signals as internal standard (CDCl3: δ 7.26
ppm). Data is reported as follows: chemical shift, integration,
multiplicity (s = singlet, d = doublet, t = triplet, q = quartet, m =
multiplet, br = broad) and coupling constants (Hz). 13C NMR
spectra were recorded on either a 100 MHz or a 125 MHz with
complete proton decoupling. Chemical shifts (δ) are reported in
ppm downfield from tetramethylsilane with the solvent as the
internal reference (CDCl3: δ 77.26 ppm). HRMS analyses were
performed with Q-TOF YA263 high resolution (Water
Corporation) instruments by +ve mode electrospray ionization.
Elemental analysis (CHN) is performed with CHNS/O
[a]The reactions were performed using 3 (0.3 mmol, 1.0 equiv), PTSA (0.3
equiv) in C6H6 (8 mL) at 80 °C for 3 h.
It is intriguing to find out that the reaction time or yields is not
influenced by the electronic character of the substrates and in all
cases, the corresponding o-terphenyls 2b-j were isolated in 75-
88% yield. The o-terphenyls containing halogen substituents
such as 2b, 2c, 2d, 2h are important precursors which can be
further employed as coupling partners in different organometallic
transformations.
Furthermore, we envisioned that C-C coupling of o-terphenyl
derivatives could afford triphenylene systems. Following
literature procedure, Scholl reaction was performed by treating
o-terphenyl with FeCl3 in CH2Cl2/CH3NO2. We observed that the
Analyzer.
.
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General procedure for the synthesis of symmetrical
benzil derivatives (GP-1): Aromatic aldehyde (1.0 equiv.) was
added to Amberlyst 15 (2.0 equiv.) and zinc dust (3.0 equiv.) in
water and the mixture was heated with constant stirring at 70 °C
for 6h. Then, the reaction mixture was filtered, extracted with
EtOAc and the pinacol product was purified by column
chromatography with EtOAC-hexane (20/80). In the next step,
the pinacol product in dry DCM was added to the solution Dess-
Martin Periodinane (DMP) (1.2 equiv.) in dry DCM and the
reaction was allowed to stir for 30 min. Finally, DMP was filtered
out and purification of the crude product by column
chromatography on silica gel with EtOAc–hexane (2/98 to 5/95)
yielded the symmetrical benzil derivative 5b-g. Compounds 5b-f
were previously reported.11
yielded compound 5f (1.87 g, 63%) as a yellow solid. Benzil 5f is
previously reported.11h
1,2-Bis(2,5-dimethoxyphenyl)ethane-1,2-dione (5g): 1H
NMR (400 MHz, CDCl3): Using the general procedure GP-1, 2,5-
dimethoxybenzaldehyde 7f (3.0 g, 18.0 mmol), Amberlyst 15
(7.6 g, 36.0 mmol) and zinc (3.55 g, 54.2 mmol) followed by
oxidation with DMP (3.5 g, 10.8 mmol) yielded compound 5g
(1.9 g, 64%) as a yellowish white solid; mp 150-153 °C; IR
(ATR) . 3006, 2943, 2838, 1658, 1609, 1495, 1417, 1274, 1221,
1158, 1041, 1016, 950, 817, 715 cm-1; 1H NMR (500 MHz,
CDCl3): 7.57 (2H, d, J = 4.0 Hz), 7.15 (2H, dd, J = 11.2, 4.0 Hz),
6.92 (2H, d, J = 11.2 Hz), 3.85 (6H, s), 3.55 (6H, s); 13C (100
MHz, CDCl3): 192.2, 155.2, 155.4, 124.1, 123.3, 114.9, 112.4,
56.9, 56.0; HRMS (ESI) calcd for C18H18NaO6 [M+Na]+:
353.1001; Found: 353.1000. Anal calcd for C18H18O6 (330.33):
calcd. C 65.45, H 5.49; found C 65.49, H 5.44.
General procedure for the synthesis of unsymmetrical
benzil derivatives (GP-2): In a round- bottomed flask, CuI (0.02
equiv.), TMEDA (0.05 equiv.) and acid chloride (1.2 equiv.) were
added sequentially to phenylacetylene (1.0 equiv.) in Et3N. The
reaction mixture was stirred for 1 h under N2 atmosphere. After
completion, the reaction was quenched with NaHCO3. The
organic layer was extracted with EtOAc and purified by column
chromatography on silica gel with EtOAc–hexane (5/95 to 10/90)
to give corresponding alkynone intermediates. In the next step,
K2CO3 (1.0 equiv.) was added to alkynones in DMSO-water
(50:1) and heated at 70 °C for 8 h under oxygen atmosphere.
After reaction was completed, water was added and extracted
with EtOAc. The organic phase was dried over Na2SO4,
concentrated and purified by column chromatography on silica
gel with EtOAc–hexane (2/98 to 5/95) to provide the
unsymmetrical benzil derivatives 5h and 5i. 5i is previously
reported.11,15
1-(2-Iodophenyl)-2-phenylethane-1,2-dione (5h): Using
the general procedure GP-2, 2-iodobenzoyl chloride 8a (3.0 g,
11.3 mmol), CuI (35.8 mg, 0.19 mmol) and TMEDA (70 µL, 0.47
mmol) followed by addition of phenylacetylene (958 mg, 9.4
mmol) yielded the intermediate alkynone (2.75 g, 88%) as a
white solid. In the next step, the alkynone (2.0 g, 6.0 mmol) and
K2CO3 (830 mg, 6.0 mmol) in O2 air gave corresponding benzil
5h (1.2 g, 60%) as a light yellow solid; mp 180-182 °C; IR (ATR)
. 2923, 2851, 1709, 1675, 1580, 150, 1291, 1249, 1022, 758,
1
701 cm-1; H NMR (500 MHz, CDCl3): 8.07 (2H, d, J = 8.4 Hz),
8.00 (1H, d, J = 7.0 Hz), 7.67 (2H, t, J = 5.0 Hz), 7.54 (2H, t, J =
8.0 Hz), 7.48 (1H, t, J = 7.5 Hz), 7.26 (1H, d, J = 7.5); 13C (125
MHz, CDCl3): 194.8, 191.4, 141.3, 138.5, 134.7, 134.1, 133.4,
133.0, 130.5, 130.0, 129.1, 129.0, 128.4, 93.3; HRMS (ESI)
calcd for C14H9INaO2 [M+Na]+: 358.9545; Found: 358.9547. Anal
calcd for C14H9IO2 (336.12): calcd. C 50.03, H 2.70; found C
50.00, H 2.78.
1,2-Bis(4-fluorophenyl)ethane-1,2-dione (5b): Using the
general procedure GP-1, 4-fluorobenzaldehyde 7a (3.0 g, 24.1
mmol), Amberlyst 15 (10.17 g, 48.2 mmol) and zinc (4.74 g, 72.3
mmol) followed by oxidation with DMP (3.5 g, 10.9 mmol)
yielded compound 5b (1.69 g, 58%) as a yellow solid. Benzil 5b
is previously reported.11c,11g-i
1-(2-Methoxyphenyl)-2-phenylethane-1,2-dione
(5i):
Using the general procedure GP-2, 2-iodobenzoyl chloride 8b
(3.0 g, 17.6 mmol), CuI (55.6 mg, 0.29 mmol) and TMEDA (108
µL g, 0.73 mmol) followed by addition of phenylacetylene (1.79 g,
14.6 mmol) yielded the intermediate alkynone (3.03 g, 88%) as a
white solid. In the next step, the alkynone (3.0 g, 12.7 mmol) and
K2CO3 (1.75 g, 12.7 mmol) in O2 air gave corresponding benzil 5i
(1.58 g, 52%) as yellow solid. Benzil 5i is previously
reported.11e,11g
1,2-Bis(2-fluorophenyl)ethane-1,2-dione (5c): Using the
general procedure GP-1, 2-fluorobenzaldehyde 7b (3.0 g, 24.1
mmol), Amberlyst 15 (10.17 g, 48.2 mmol) and zinc (4.74 g, 72.3
mmol) followed by oxidation with DMP (3.7 g, 11.5 mmol)
yielded compound 5c (1.75 g, 60%) as a light yellow solid.
Benzil 5c is previously reported.11c,11g
General procedure for the synthesis of diallylated
products from benzils (GP-3): To a solution of benzil 5 (1.0
equiv.) in dry THF, allyl magnesium halide solution (3.0 equiv.)
was added dropwise at 0 °C and stirred at room temperature for
6 h. The reaction mixture was quenched with saturated aqueous
NH4Cl solution and extracted with ethyl acetate (3 x 20 mL). The
combined organic phase was washed with brine, dried over
anhydrous Na2SO4, filtered and concentrated in vacuum. The
crude residue was then purified by column chromatography on
silica gel with EtOAc–hexane (10/90 to 15/85) to give compound
4.
1,2-Bis(4-chlorophenyl)ethane-1,2-dione (5d): Using the
general procedure GP-1, 4-chlorobenzaldehyde 7c (3.0 g, 21.3
mmol), Amberlyst 15 (9.0 g, 42.7 mmol) and zinc (4.18 g, 63.9
mmol) followed by oxidation with DMP (3.34 g, 10.3 mmol)
yielded compound 5d (1.9 g, 65%) as a yellow solid. Benzil 5d is
previously reported.11i
1,2-Bis(4-methylphenyl)ethane-1,2-dione (5e): Using the
general procedure GP-1, 4-methylbenzaldehyde 7d (3.0 g, 25.0
mmol), Amberlyst 15 (10.5 g, 50.0 mmol) and zinc (4.9 g, 75.0
mmol) followed by oxidation with DMP (3.4 g, 10.3 mmol)
yielded compound 5e (1.84 g, 62%) as a white solid. Benzil 5e is
previously reported.11g-i
4,5-Diphenylocta-1,7-diene-4,5 diol (4a): Using the general
procedure GP-3, benzil 5a (1.0 g, 4.75 mmol) and allyl
magnesium bromide (14.25 mL, 14.25 mmol) yielded compound
1,2-Bis(3-methoxyphenyl)ethane-1,2-dione (5f): Using the
general procedure GP-1, 3-methoxybenzaldehyde 7e (3.0 g,
22.0 mmol), Amberlyst 15 (9.28 g, 44.0 mmol) and zinc (4.32 g,
66.0 mmol) followed by oxidation with DMP (4.27 g, 11.2 mmol)
1
4a (845 mg, 60%) as a colorless oil; H NMR (500 MHz, CDCl3):
7.39 (4H, d, J = 7.1 Hz), 7.30-7.23 (6H, m), 5.35-5.27 (2H, m),
4.97-4.93 (4H, m), 3.18 (2H, dd, J = 14.2, 5.4 Hz), 2.31 (2H, s),
2.22 (2H, dd, J = 14.2, 8.9 Hz); 13C (125 MHz, CDCl3): 142.1,
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10.1002/ejoc.201900988
European Journal of Organic Chemistry
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134.0, 128.0, 127.5, 127.0, 119.6, 79.7, 41.0; HRMS (ESI) calcd
for C20H23O2 [M+H]+: 295.1698; Found: 295.1694. Compound 4a
is previously reported.18
2.79 (2H, dd, J = 14.4, 9.0 Hz), 2.54 (2H, dd, J = 14.4, 5.4 Hz);
13C (100 MHz, CDCl3): 158.9, 142.3, 134.3, 128.1, 121.1, 119.7,
114.3, 112.9, 80.0, 55.2, 40.5; HRMS (ESI) calcd for
C22H26NaO4 [M+Na]+: 377.1729; Found: 377.1729.
4,5-Bis(4-fluorophenyl)octa-1,7-diene-4,5-diol (4b): Using
the general procedure GP-3, benzil 5b (1.0 g, 4.06 mmol) and
allyl magnesium bromide (12.18 mL, 12.18 mmol) yielded
4,5-Bis(2,5-dimethoxyphenyl)octa-1,7-diene-4,5-diol (4g):
Using the general procedure GP-3, benzil 5g (1.0 g, 3.02 mmol)
and allyl magnesium bromide (9.0 mL, 9.0 mmol) yielded the
compound 4g (880 mg, 70%) as colourless liquid; IR (ATR) .
3372, 2957, 2926, 2857, 1742, 1666, 1618, 1495, 1466, 1184,
1081, 967, 837, 772 cm-1; 1H NMR (400 MHz, CDCl3): 6.71 (4H,
m), 6.33 (1H, s), 5.93 (1H, s), 5.70-5.45 (2H, m), 5.04 (2H, d, J =
16.9 Hz ), 4.94 (2H, d, J = 9.6 Hz), 3.77 (2H, s br), 3.60 (6H, s),
3.42 (6H, s), 2.86-2.81 (4H,m); 13C (100 MHz, CDCl3): 153.8,
152.8, 135.5, 129.6, 117.2, 117.0, 113.0, 112.9, 85.5, 56.6, 55.7,
39.6; HRMS (ESI) calcd for C24H30NaO6 [M+Na]+: 437.1940;
Found: 437.1942.
1
compound 4b (910 mg, 68%) as a colorless oil; H NMR (400
MHz, CDCl3): 7.09 (4H, s br), 6.93 (4H, t, J = 8.5 Hz), 5.42-5.32
(2H, m), 5.11 (2H, d, J = 17.0 Hz), 5.04 (2H, d, J = 10.0 Hz),
2.84 (2H, s), 2.80 (2H, dd, J = 14.3, 8.8 Hz), 2.52 (2H, dd, J =
14.2, 5.1 Hz), 13C (100 MHz, CDCl3): 162.1 (d, JC-F = 150.0 Hz),
136.2 (d, JC-F = 3.2 Hz), 133.8, 130.0 (d, JC-F = 7.9 Hz), 120.1,
114.1 (d, JC-F = 20.9 Hz), 79.6, 40.2; HRMS (ESI) calcd for
C20H20F2NaO2 [M+Na]+: 353.1329; Found: 353.1327. Compound
4b is previously reported.18
4,5-Bis(2-fluorophenyl)octa-1,7-diene-4,5-diol (4c): Using
the general procedure GP-3, benzil 5c (1.0 g, 4.06 mmol) and
allyl magnesium bromide (12.18 mL, 12.18 mmol) yielded
compound 4c (865 mg, 65%) as a colorless liquid; IR (ATR) .
3539, 3077, 1639, 1613, 1578, 1448, 1442, 1269, 1211, 994,
4-(2-Iodophenyl)-5-phenylocta-1,7-diene-4,5-diol
(4h):
Using the general procedure GP-3, benzil 5h (1.0 g, 2.97 mmol)
and allyl magnesium bromide (8.92 mL, 8.92 mmol) yielded the
compound 4h (750 mg, 60%) as a colourless liquid; IR (ATR) .
3493, 3010, 1635, 1610, 1572, 1450, 1433, 1262, 1201, 962,
1
917, 820, 753 cm-1; H NMR (400 MHz, CDCl3): 7.54 (1H, s br),
1
7.28-7.17 (3H, m), 7.10 (1H, t, J = 7.5 Hz), 6.97-6.82 (3H, m),
5.60-5.47 (2H, m), 5.12 (2H, t, J = 16.5 Hz), 5.00 (2H, t, J = 10.0
Hz), 3.47 (1H, s br), 3.18 (1H, d, J = 9.4 Hz), 2.97 (2H, s br), 2.62-
2.55 (2H, m); 13C (100 MHz, CDCl3): 134.2 (d, JC-F = 10.0 Hz),
131.3 (dd, JC-F = 14.5, 4.0 Hz), 129.6 (dd, JC-F = 21.3, 9.0 Hz),
127.8 (d, JC-F = 12.2 Hz), 123.7 (d, JC-F = 3.0 Hz), 123.3 (d, JC-F
= 3.0 Hz), 119.3 (d, JC-F = 10.1 Hz), 115.9 (d, JC-F = 25.6 Hz),
80.6, 39.8, 39.7; HRMS (ESI) calcd for C20H20F2NaO2 [M+Na]+:
353.1329; Found: 353.1328.
820, 783 cm-1; H NMR (500 MHz, CDCl3): 7.39 (3H, d, J = 7.1
Hz), 7.30-7.27 (4H, m), 7.25-7.23 (2H, m), 5.35-5.27 (2H, m),
4.97-4.93 (4H, m), 3.18 (2H, dd, J = 8.5, 5.5 Hz), 2.31 (2H, s),
2.23 (2H, dd, J = 8.5, 5.5 Hz); 13C (125 MHz, CDCl3): 142.3,
134.0, 128.5, 128.1, 127.5, 127.2, 127.0, 119.5, 79.8, 41.1;
HRMS (ESI) calcd for C20H21INaO2 [M+Na]+: 443.0484; Found:
443.0482.
4-(2-Methoxyphenyl)-5-phenylocta-1,7-diene-4,5-diol (4i):
Using the general procedure GP-3, benzil 5i (1.0 g, 4.16 mmol)
and allyl magnesium bromide (12.5 mL, 12.5 mmol) yielded
compound 4i (810 mg, 60%) as a colorless liquid; IR (ATR) .
3465, 3072, 3009, 2976, 1638, 1581, 1489, 1435, 1232, 1180,
1050, 1022, 910, 752, 702 cm-1; 1H NMR (500 MHz, CDCl3):
7.69 (1H, dd, J = 7.7, 1.6 Hz), 7.49-7.47 (2H, m), 7.31-7.30 (3H,
m), 7.00-6.97 (3H, m), 6.00-5.91 (1H, m), 5.47-5.38 (1H, m),
5.13 (2H, d, J = 13.6 Hz), 4.90 (2H, s br), 3.95 (3H, s), 3.37 (2H,
4,5-Bis(4-chlorophenyl)octa-1,7-diene-4,5-diol (4d): Using
the general procedure GP-3, benzil 5d (1.0 g, 3.58 mmol) and
allyl magnesium bromide (10.75 mL, 10.75 mmol) yielded
compound 4d (820 mg, 63%) as a colorless liquid; IR (ATR) .
3501, 3022, 1638, 1601, 1583, 1443, 1438, 1257, 1188, 977,
907, 822, 761 cm-1; 1H NMR (500 MHz, CDCl3): 7.21 (4H, d, J =
8.9 Hz), 7.07 (4H, s br), 5.40-5.31 (2H, m), 5.10 (2H, d, J = 16.7
Hz), 5.04 (2H, d, J = 10.1 Hz), 2.85 (2H, s br), 2.78 (2H, dd, J =
8.8, 5.6 Hz), 2.52 (2H, dd, J = 8.8, 5.6 Hz); 13C (125 MHz,
CDCl3): 139.1, 133.6, 133.5, 129.8, 127.5, 120.2, 79.7, 40.2;
HRMS (ESI) calcd for C20H21Cl2O2 [M+H]+: 363.0919; Found:
363.0914.
s
br), 3.04-2.95 (4H, m); 13C (125 MHz, CDCl3): 156.8, 142.3,
133.3, 131.9, 131.0, 129.2, 128.9, 128.3, 128.0, 127.1, 126.7,
121.1, 118.5, 111.9, 86.1, 81.3, 55.6, 47.2, 40.0; HRMS (ESI)
calcd for C21H24NaO3 [M+Na]+: 347.1623; Found: 347.1622.
Zinc mediated allylation of benzil 5a: To a solution of
benzil 5a (2.0 g, 9.5 mmol) in THF-H2O (4 mL-1mL) was added
zinc (2.0 g, 30.4 mmol), allyl bromide (3.3 mL, 38.0 mmol) and
NaI (3.4 g, 22.8 mmol). The reaction was stirred vigorously at
room temperature for 6 h. After completion of the reaction, the
aqueous phase was extracted with CH2Cl2, concentrated and
the product was purified by column chromatography on silica gel
with EtOAc–hexane (5/95) to give exclusively the monoallyl
compound 6a (2.11 g, 88%) as a white solid; 1H NMR (500 MHz,
CDCl3): 7.72 (2H, dd, J = 8.3, 1.0 Hz), 7.51-7.49 (2H, m), 7.43
(1H, t, J = 9.8 Hz), 7.38 (2H, t, J = 7.6 Hz), 7.32-7.27 (3H, m),
5.77-5.69 (1H, m), 5.12 (1H, d, J = 10.9 Hz), 5.02 (1H, dd, J =
17.2, 1.5 Hz), 3.13 (1H, dd, J = 13.7, 7.5 Hz), 2.97 (1H, dd, J =
13.7, 6.9 Hz); 13C (100 MHz, CDCl3): 200.9, 141.9, 134.8, 132.8,
132.4, 130.2, 129.0, 128.2, 128.1, 125.8, 120.4, 81.6, 44.1;
HRMS (ESI) calcd for C17H17O2 [M+H]+: 253.1229; Found:
253.1225.
4,5-Di-p-tolylocta-1,7-diene-4,5-diol (4e): Using the
general procedure GP-3, benzil 5e (1.0 g, 4.2 mmol) and allyl
magnesium bromide (12.6 mL, 12.6 mmol) yielded compound 4e
(745 mg, 55%) as a white solid; 1H NMR (400 MHz, CDCl3): 7.27
(4H, d, J = 7.8 Hz), 7.10 (4H, d, J = 7.8 Hz), 5.37-5.26 (2H, m),
4.97-4.91 (4H, m), 3.14 (2H, dd, J = 14.1, 5.2 Hz), 2.34 (6H, s),
2.22 (2H, s), 2.19-2.16 (2H, m); 13C (100 MHz, CDCl3): 139.1,
136.4, 134.2, 128.3, 127.9, 119.3, 79.7, 41.0, 21.1; HRMS (ESI)
calcd for C22H26NaO2 [M+Na]+: 345.1830; Found: 345.1830.
Compound 4e is previously reported.18
4,5-Bis(3-methoxyphenyl)octa-1,7-diene-4,5-diol
(4f):
Using the general procedure GP-3, benzil 5f (1.0 g, 3.7 mmol)
and allyl magnesium bromide (11.1 mL, 11.1 mmol) yielded
compound 4f (855 mg, 65%) as a colorless liquid; IR (ATR) .
3533, 2938, 1677, 1637, 1599, 1581, 1486, 1430, 1244, 1041,
1
995, 835, 758 cm-1; H NMR (500 MHz, CDCl3): 7.16 (2H, t, J =
8.0 Hz), 6.80-6.75 (6H, m), 5.45-5.37 (2H, m), 5.10 (2H, d, J =
16.8 Hz), 5.02 (2H, d, J = 10.1 Hz), 3.73 (6H, s), 2.90 (2H, s),
Synthesis of compound 4a from 6a: To a solution of
monoallyl compound 6a (1.0 g, 3.96 mmol) in dry THF, allyl
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900988
European Journal of Organic Chemistry
FULL PAPER
magnesium halide solution (5.94 mL, 5.94 mmol) was added
dropwise at 0 °C and stirred at room temperature for 6 h. The
reaction mixture was quenched with saturated aqueous NH4Cl
solution and extracted with ethyl acetate (3 x 20 mL). The
combined organic phase was washed with brine, dried over
anhydrous Na2SO4, filtered and concentrated in vacuum. The
crude residue was then purified by column chromatography on
silica gel with EtOAc–hexane (5/95) to give compound 4a (793
mg, 68%) as a colorless oil.
127.3, 126.8, 126.5, 125.3, 76.6, 38.7; HRMS (ESI) calcd for
C18H18NaO2 [M+Na]+: 289.1204; Found: 289.1206.
1,2-Bis(4-fluorophenyl)cyclohex-4-ene-1,2-diol
(3b):
Using general procedure GP-4, compound 4b (800 mg, 2.4
mmol) and Grubbs’ second generation catalyst (G-II) (98.7 mg,
0.12 mmol) provided compound 3b (617 mg, 85%) as a
colorless liquid; IR (ATR) . 3460, 3081, 2932, 2864, 1771, 1684,
1600, 1508, 1450, 1411, 1230, 1160, 1093, 1032, 1019, 889,
1
834, 814, 580 cm-1; H NMR (500 MHz, CDCl3): 7.29-7.26 (4H,
Indium promoted allylation of benzil 5a: To a solution of
benzil 5a (2.0 g, 9.51 mmol) in THF-H2O (4 mL-1mL) was added
m), 6.79 (4H, t, J = 8.7 Hz), 5.93 (2H, m), 3.29 (2H, d, J = 17.0
Hz), 2.24 (2H, d, J = 17.0 Hz), 2.15 (2H, s); 13C (125 MHz,
indium ingots (1.53 g, 13.3 mmol), 2-methylallyl bromide (1.9 mL, CDCl3): 162.0 (d, JC-F = 243.9 Hz), 138.8 (d, JC-F = 3.3 Hz), 128.3
19.0 mmol) and NaI (1.7 g, 11.4 mmol). The reaction was stirred
vigorously at room temperature for 3 h. After completion of the
reaction, the aqueous phase was extracted with CH2Cl2,
concentrated and the product was purified by column
chromatography on silica gel with EtOAc–hexane (5/95) to give
(d, JC-F = 7.9 Hz), 125.3, 114.1 (d, JC-F = 20.8 Hz), 76.3, 39.0;
HRMS (ESI) calcd for C18H16F2NaO2 [M+Na]+: 325.1016; Found:
325.1014.
1,2-Bis(2-fluorophenyl)cyclohex-4-ene-1,2-diol
(3c):
Using general procedure GP-4, compound 4c (800 mg, 2.4
mmol) and Grubbs’ second generation catalyst (G-II) (98.7 mg,
0.12 mmol) provided compound 3c (602 mg, 83% ) as a
colorless liquid; IR (ATR) . 3593, 3033, 2915, 1613, 1577, 1497,
1447, 1331, 1273, 1210, 1034, 883, 748, 654 cm-1; 1H NMR (500
MHz, CDCl3): 7.36 (2H, t, J = 10.0 Hz), 7.24-7.21 (2H, m), 7.05
(2H, t, J = 9.5 Hz), 6.81 (2H, dd, J = 17.0, 10.2 Hz), 5.93 (2H, s),
2.92 (2H, d, J = 21.3 Hz), 2.64 (2H, d, J = 22.5 Hz); 13C (100
MHz, CDCl3): 160.2 (d, JC-F = 242.8 Hz), 129.8 (d, JC-F = 9.5 Hz),
129.4 (d, JC-F = 3.7 Hz), 129.2 (d, JC-F = 6.9 Hz), 125.4, 124.0 (d,
JC-F = 3.1 Hz), 116.4 (d, JC-F = 26.2 Hz), 78.5 (d, JC-F = 3.6 Hz),
37.4; HRMS (ESI) calcd for C18H16F2NaO2 [M+Na]+: 325.1016;
Found: 325.1014.
1
benzoin derivative 6b (2.53 g, 90%) as a white solid. H NMR
(500 MHz, CDCl3): 7.80 (2H, dd, J = 8.5, 1.3 Hz), 7.55-7.53 (2H,
m), 7.44-7.41 (1H, m), 7.38-7.35 (2H, m), 7.31-7.28 (3H, m),
4.89 (1H, s), 4.63 (1H, s), 3.24 (1H, d, J = 14.3 Hz), 2.94 (1H, d,
J = 13.6 Hz), 1.54 (3H, s); 13C (125 MHz, CDCl3): 201.1, 142.5,
141.6, 132.7, 130.4, 128.9, 128.1, 127.9, 127.8, 127.5, 127.3,
125.6, 116.7, 81.4, 47.6, 24.3; HRMS (ESI) calcd for C18H19O2
[M+H]+: 267.1385; Found: 267.1387.
Synthesis of compound 4j from 6b:To a solution of benzoin
derivative 6b (1.0 g, 3.76 mmol) in dry THF, allyl magnesium
bromide solution (5.6 mL, 5.6 mmol) was added dropwise at
0 °C and stirred at room temperature for 6 h. The reaction
mixture was quenched with saturated aqueous NH4Cl solution
and extracted with ethyl acetate (3 x 20 mL). The combined
organic phase was washed with brine, dried over anhydrous
Na2SO4, filtered and concentrated in vacuum. The crude residue
was then purified by column chromatography on silica gel with
EtOAc–hexane (5/95) to give compound 4j (753 mg, 65%) as a
colorless liquid; IR (ATR) . 3522, 3071, 3026, 2975, 1637, 1492,
1445, 1374, 1327, 1222, 1181, 1059, 995, 907, 763, 717, 701
cm-1; 1H NMR (500 MHz, CDCl3): 7.22 (10H, s br), 5.48-5.40 (1H,
m), 5.04 (1H, d, J = 17.1 Hz), 4.97 (1H, d. J = 10.2 Hz), 4.83 (1H,
s), 4.71 (1H, s), 2.99 (1H, d, J = 14.0 Hz), 2.78 (1H, dd, J = 14.6,
8.3 Hz), 2.46 (1H, dd, J = 14.6, 5.8 Hz), 2.38 (1H, d, J = 14.0
Hz), 1.18 (3H, s); 13C (125 MHz, CDCl3): 143.0, 141.3, 140.3,
134.5, 128.8, 128.4, 127.2, 127.1, 127.0, 118.9, 116.4, 80.1,
79.1, 43.4, 40.3, 24.4; HRMS (ESI) calcd for C21H24NaO2
[M+Na]+: 331.1674; Found: 331.1672.
1,2-Bis(4-chlorophenyl)cyclohex-4-ene-1,2-diol
(3d):
Using general procedure GP-4, compound 4d (800 mg, 2.2
mmol) and Grubbs’ second generation catalyst (G-II) (90.5 mg,
0.11 mmol) provided compound 3d (575 mg, 78%) as a
colorless liquid; IR (ATR) . 3574, 3038, 2925, 1596, 1490, 1400,
1304, 1174, 1093, 1031, 988, 890, 826, 757, 731, 670, 569, 480
1
cm-1; H NMR (500 MHz, CDCl3): 7.27 (4H, d, J = 8.5 Hz), 7.06
(4H, d, J = 8.5 Hz), 5.92 (2H, s), 3.25 (2H, d, J = 16.9 Hz), 2.23
(2H, dd, J .= 15.0, 2.5 Hz); 13C (100 MHz, CDCl3): 141.5, 132.9,
128.0, 127.4, 125.2, 76.3, 39.0; HRMS (ESI) calcd for
C18H16Cl2NaO2 [M+Na]+: 357.0425; Found: 357.0426.
1,2-Di-p-tolylcyclohex-4-ene-1,2-diol (3e): Using general
procedure GP-4, compound 4e (700 mg, 2.2 mmol) and Grubbs’
second generation catalyst (G-II) (90.5 mg, 0.11 mmol) provided
compound 3e (453 mg, 70%) as a colorless liquid; IR (ATR) .
3584, 3026, 2921, 2857, 1709, 1657, 1511, 1444, 1416, 1363,
1183, 1080, 1031, 984, 888, 816, 729, 698, 661, 582, 465 cm-1;
1H NMR (500 MHz, CDCl3): 7.38 (4H, d, J = 8.2 Hz), 7.16 (4H, d,
J = 7.9 Hz), 5.81 (2H, s), 2.93 (2H, d, J = 16.5 Hz), 2.73 (2H, d,
J = 16.5 Hz), 2.34 (6H, s); 13C (125 MHz, CDCl3): 140.3, 136.3,
128.1, 126.5, 125.4, 76.5, 39.0, 21.0; HRMS (ESI) calcd for
C20H23O2 [M+H]+: 295.1698; Found: 295.1693.
General procedure for ring closing metathesis (GP-4): To
a stirred solution of 4 (1.0 equiv.) in dry dichloromethane,
Grubbs’ second generation catalyst (G-II) (5 mol %) was added
and stirred at room temperature for 15 h under an argon
atmosphere. The reaction mixture was then concentrated and
purified by column chromatography using silica gel with EtOAc–
hexane (15/85 to 20/80) to yield the tricyclic compound 3.
1,2-Bis(3-methoxyphenyl)cyclohex-4-ene-1,2-diol
(3f):
1,2-Diphenylcyclohex-4-ene-1,2-diol (3a): Using general
procedure GP-4, compound 4a (800 mg, 2.7 mmol) and Grubbs’
second generation catalyst (G-II) (11.2 mg, 0.13 mmol) provided
compound 3a (560 mg, 78%) as a colorless liquid; IR (ATR) .
3560, 3026, 2924, 2850, 1493, 1446, 1068, 1029, 886, 725, 698
Using general procedure GP-4, compound 4f (800 mg, 2.2) and
Grubbs’ second generation catalyst (G-II) (90.5 mg, 0.11 mmol)
provided compound 3f (560 mg, 78%) as a colorless liquid; IR
(ATR) . 3475, 3035, 2936, 2834, 1687, 1600, 1582, 1464, 1429,
1289, 1252, 1158, 1032, 972, 894, 870, 782, 697, 662, 608 cm-1;
1H NMR (500 MHz, CDCl3): 7.07 (2H, t, J = 7.9 Hz), 6.97 (2H, d,
J = 7.8 Hz), 6.88 (2H, s), 6.67 (2H, d, J = 8.0 Hz), 5.93 (2H, s),
3.63 (6H, s), 3.30 (2H, d, J = 16.8 Hz), 2.26 (2H, d, J = 17.1 Hz),
1
cm-1; H NMR (500 MHz, CDCl3): 7.33-7.30 (4H, m), 7.12-7.10
(6H, m), 5.95 (2H, m), 3.34 (2H, d, J = 20.9 Hz), 2.27 (2H, dd, J
= 18.3, 3.3 Hz), 2.17 (2H, s); 13C (100 MHz, CDCl3): 143.0,
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900988
European Journal of Organic Chemistry
FULL PAPER
2.19 (2H, s); 13C (125 MHz, CDCl3): 159.0, 144.8, 128.2, 125.3,
118.9, 112.7, 112.5, 76.0, 55.3, 38.7; HRMS (ESI) calcd for
C20H23O4 [M+H]+: 327.1596; Found: 327.1591.
mmol) provided compound 2a (337 mg, 77%) as a viscous
colorless liquid; H NMR (500 MHz, CDCl3): 7.42 (4H, m), 7.21-
7.19 (6H, m), 7.15-7.12 (4H, m); 13C (125 MHz, CDCl3): 141.7,
140.7, 130.7, 130.0, 127.9, 127.6, 126.6; HRMS (ESI) calcd for
C18H15 [M+H]+: 231.1174; Found: 231.1169. o-Terphenyl 2a is
previously reported. 11f
1
1,2-Bis(2,5-dimethoxyphenyl)cyclohex-4-ene-1,2-diol
(3g): Using general procedure GP-4, compound 4g (800 mg, 1.9
mmol) and Grubbs’ second generation catalyst (G-II) (80.0 mg,
0.1 mmol) provided compound 3g (605 mg, 82%) as a colorless
liquid; IR (ATR) . 3460, 3078, 2941, 2838, 1593, 1496, 1463,
1408, 1281, 1220, 1178, 1045, 905, 814, 730 cm-1; 1H NMR (400
MHz, CDCl3): 7.21 (2H, s), 6.67 (4H, m), 6.01 (2H, s), 5.87 (2H,
s), 3.67 (12H, s), 3.13 (2H, d, J = 16.8 Hz), 2.28 (2H, d, J = 17.1
Hz); 13C (100 MHz, CDCl3): 153.8, 151.3, 133.6, 125.3, 115.7,
112.6, 112.5, 79.8, 56.4, 55.8, 37.9; HRMS (ESI) calcd for
C22H26NaO6 [M+Na]+: 409.1627; Found: 409.1625.
4,4”-Difluoro-o-terphenyl (2b): Using the general
procedure GP-5, compound 3b (500 mg, 1.6 mmol) and PTSA
(82.6 mg, 0.48 mmol) provided compound 2b (355 mg, 84%) as
a colorless solid; 1H NMR (500 MHz, CDCl3): 7.42-7.37 (4H, m),
7.07 (4H, dd, J = 8.6, 3.2 Hz), 6.91 (4H, t, J = 8.6 Hz); 13C (125
MHz, CDCl3): 161.9 (d, JC-F = 244.4 Hz), 139.7, 137.5, 131.54 (d,
JC-F = 7.7 Hz), 130.6, 127.8, 115.0 (d, JC-F = 21.2 Hz); HRMS
(ESI) calcd for C18H12NaF2 [M+Na]+: 289.0805; Found: 289.0800.
o-Terphenyl 2b is previously reported. 6h
1-(2-Iodophenyl)-2-phenylcyclohex-4-ene-1,2-diol
(3h):
Using general procedure GP-4, compound 4h (700 mg, 1.6
mmol) and Grubbs’ second generation catalyst (G-II) (68.5 mg,
0.08 mmol) provided compound 3h (490 mg, 75%) as a
2,2”-Difluoro-o-terphenyl (2c): Using the general
procedure GP-5, compound 3c (500 mg, 1.6 mmol) and PTSA
(82.6 mg, 0.48 mmol) provided compound 2c (360 mg, 85%) as
colorless liquid; IR (ATR) . 3534, 3061, 3027, 2923, 2847, 1601, a colorless solid; mp 90-94 °C; IR (ATR) . 2923, 2853, 1730,
1
1495, 1446, 1362, 1177, 1053, 986, 920, 876, 740, 700, 662 cm-
1493, 1469, 1239, 1216, 753 cm-1; H NMR (500 MHz, CDCl3):
1; 1H NMR (500 MHz, CDCl3): 7.20 (2H, t, J = 7.2 Hz), 7.16 (4H, t, 7.47-7.42 (4H, m), 7.18 (2H, m), 7.11 (2H, t, J = 7.0 Hz), 6.99
J = 7.5 Hz), 7.01 (3H, d, J = 7.8 Hz), 6.00 (2H, m), 2.89 (2H, d, J
(2H, t, J = 7.4 Hz), 6.91 (2H, t, J = 9.1 Hz); 13C (125 MHz,
= 17.1 Hz), 2.82 (2H, s), 2.58 (2H, d, J = 18.2 Hz); 13C (100 MHz, CDCl3): 159.7 (d, JC-F = 250.0 Hz), 135.8, 131.9, 130.8, 129.0 (d,
CDCl3): 142.3, 127.3, 127.1, 126.9, 126.4, 77.08, 39.4; HRMS
(ESI) calcd for C18H18IO2 [M+H]+: 393.0351; Found: 393.0344.
JC-F = 8.7 Hz), 127.9, 123.6, 115.4 (d, JC-F = 22.2 Hz); HRMS
(ESI) calcd for C18H12NaF2 [M+Na]+: 289.0805; Found: 289.0802.
Anal calcd for C18H12F2 (266.28): calcd. C 81.19, H 4.54; found
C 81.17, H 4.59.
1-(2-Methoxyphenyl)-2-phenylcyclohex-4-ene-1,2-diol
(3i): Using general procedure GP-4, compound 4i (700 mg, 2.2
mmol) and Grubbs’ second generation catalyst (G-II) (90.5 mg,
0.11 mmol) provided compound 3i (490 mg 75%) as a colorless
liquid; IR (ATR) . 3488, 3058, 2932, 2844, 1598, 1477, 1443,
1400, 1278, 1223, 1166, 1035, 911, 828, 703 cm-1; 1H NMR (500
4,4”-Dichloro-o-terphenyl (2d): Using the general
procedure GP-5, compound 3d (500 mg, 1.5 mmol) and PTSA
(77.5 mg, 0.45 mmol) provided compound 2d (360 mg, 80%) as
a white solid; mp 108-112 °C; IR (ATR) . 2951, 2922, 2852,
MHz, CDCl3): 7.54 (1H, dd, J = 7.8, 1.6 Hz), 7.22 (1H, dt, J = 8.1, 1602, 1465, 1376, 1091, 1006, 830, 758 cm-1; 1H NMR (500
1.6 Hz), 7.16-7.15 (3H, m), 6.98-6.93 (3H, m), 6.57 (1H, d, J =
8.9 Hz), 6.05-6.02 (1H, m), 5.85-5.82 (1H, m), 3.03 (3H, s), 2.76
(2H, m), 2.70 (1H, d, J = 18.7 Hz), 2.41 (1H, dd, J = 17.8, 4.5
Hz); 13C (100 MHz, CDCl3): 157.2, 143.7, 130.6, 129.1, 127.9,
127.1, 127.0, 126.9, 126.8, 125.0, 121.3, 110.9, 79.7, 77.2, 55.0,
40.5, 35.9; HRMS (ESI) calcd for C21H24NaO3 [M+Na]+:
347.1623; Found: 347.1622.
MHz, CDCl3): 7.42-7.37 (4H, m), 7.24 (4H, d, J = 8.4 Hz), 7.05
(4H, d, J = 8.4 Hz); 13C (100 MHz, CDCl3): 139.8, 139.4, 133.0,
131.2, 130.6, 128.4, 128.0; HRMS (ESI) calcd for C18H13Cl2
[M+H]+: 299.0394; Found: 299.0350. Anal calcd for C18H12Cl2
(299.19): calcd. C 72.26, H 4.04; found C 72.20, H 4.00.
4,4”-Dimethyl-o-terphenyl (2e): Using the general
procedure GP-5, compound 3e (400 mg, 1.3 mmol) and PTSA
(67.2 mg, 0.39 mmol) provided compound 2e (255 mg, 76%) as
a colorless solid; 1H NMR (500 MHz, CDCl3): 7.40-7.36 (4H, m),
7.05-7.01 (8H, m), 2.31 (6H, s); (100 MHz, CDCl3): 140.6, 138.9,
136.1, 130.7, 129.8, 128.7, 127.3, 21.2; HRMS (ESI) calcd for
C20H18Na [M+Na]+: 281.1306; Found: 281.1300. o-Terphenyl 2e
is previously reported. 6i
4-Methyl-1,2-diphenylcyclohex-4-ene-1,2-diol (3j): Using
general procedure GP-4, compound 4j (700 mg, 2.3 mmol) and
Grubbs’ second generation catalyst (G-II) (90.5 mg, 0.11 mmol)
1
provided compound 3j (477 mg, 74%) as a colorless liquid; H
NMR (400 MHz, CDCl3): 7.31 (4H, s br), 7.10 (6H, s br), 5.63 (1H,
s), 3.28 (2H, t, J = 14.6 Hz), 2.18 (2H, d, J = 7.6 Hz), 1.86 (3H,
s); 13C (100 MHz, CDCl3): 143.0, 132.8, 127.3, 126.8, 126.6,
126.5, 118.9, 76.3, 43.5, 38.7, 23.6; HRMS (ESI) calcd for
C19H20KO2 [M+K]+: 319.1100; Found: 319.1101. Diol 3j is
previously reported.8d
3,3”-Dimethoxy-o-terphenyl (2f): Using the general
procedure GP-5, compound 3f (500 mg, 1.5 mmol) and PTSA
(77.5 mg, 0.45 mmol) provided compound 2f (384 mg, 88%) as
a colorless solid; 1H NMR (500 MHz, CDCl3): 7.46-7.40 (4H, m),
7.14 (2H, t, J = 7.9 Hz), 6.79-6.74 (4H, m), 6.69-6.68 (2H, m),
3.62 (6H, s); 13C (100 MHz, CDCl3): 159.2, 143.0, 140.6, 130.5,
129.0, 127.6, 122.4, 115.3, 112.8, 55.2; HRMS (ESI) calcd for
C20H18NaO2 [M+Na]+: 313.1204; Found: 313.1207. o-Terphenyl
2f is previously reported. 12e
General procedure for dehydrative aromatization (GP-5):
PTSA (30 mol %) was added to a solution of compound 3 in
benzene and the resulting mixture was stirred at 80 °C for 3 h.
The reaction mixture was concentrated and extracted with
EtOAc (3 x 20 mL). The combined organic extracts were dried
over Na2SO4, filtered and concentrated. Purification by column
chromatography on silica gel with EtOAc–hexane (2/98 to 5/95)
afforded compound 2.
2,2”,5,5”-Tetramethoxy-o-terphenyl (2g): Using the
general procedure GP-5, compound 3g (500 mg, 1.29 mmol)
and PTSA (66.8 mg, 0.39 mmol) provided compound 2g (384
mg, 85%)) as a colorless solid; mp 75-78 °C; IR (ATR) . 2960,
2923, 2853, 1733, 1648, 1612, 1462, 1260, 1086, 1018, 842,
o-Terphenyl (2a): Using the general procedure GP-5,
compound 3a (500 mg, 1.9 mmol) and PTSA (96 mg, 0.56
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10.1002/ejoc.201900988
European Journal of Organic Chemistry
FULL PAPER
1
799 cm-1; H NMR (500 MHz, CDCl3): 7.42-7.38 (4H, m), 6.71-
m), 6.88 (2H, d, J = 8.5 Hz), 6.58 (1H, d, J = 8.1 Hz), 3.33 (3H,
s); 13C (100 MHz, CDCl3): 154.7, 142.3, 141.8, 137.5, 133.5,
132.3, 131.0, 130.6, 129.8, 129.1, 128.8, 127.6, 127.5, 127.2,
126.2, 110.9, 55.2; HRMS (ESI) calcd for C19H14NaO [M+Na]+:
281.0942; Found: 281.0944. Triphenylene 1i is previously
reported.6g
6.65 (6H, m), 3.62 (6H, s), 3.47 (6H, s); 13C (125 MHz, CDCl3):
153.0, 150.8, 138.1, 131.7, 130.6, 127.3, 117.0, 113.5, 111.5,
55.8, 55.7; HRMS (ESI) calcd for C22H23O4 [M+H]+: 351.1596;
Found: 351.1590. Anal calcd for C22H22O4 (350.40): calcd. C
75.41, H 6.33; found C 75.45, H 6.39.
2-Iodo-o-terphenyl (2h): Using the general procedure GP-5,
compound 3h (400 mg, 1.0 mmol) and PTSA (51.6 mg, 0.3
mmol) provided compound 2h (292 mg, 82%) as a colorless
solid; mp 80-83 °C; IR (ATR) . 2957, 2921, 2852, 1712, 1462,
1377, 1260, 1103, 1021, 802, 759, 746, 699 cm-1; 1H NMR (500
MHz, CDCl3): 7.45-7.40 (4H, m), 7.21-7.18 (5H, m), 7.14-7.12
(4H, m); 13C (100 MHz, CDCl3): 141.7, 140.7, 130.7, 130.0,
127.9, 127.6, 126.5; HRMS (ESI) calcd for C18H14I [M+H]+:
357.0140; Found: 357.0156. Anal calcd for C18H13I (356.20):
calcd. C 60.69, H 3.68; found C 60.61, H 3.64.
Acknowledgements ((optional))
We thank DST India for research funding. JD thanks DST for a
SwarnaJayanti fellowship. SK and TM thank CSIR-India for
research fellowships.
Keywords: Aromatization · Benzil · Ring closing metathesis · o-
Terphenyl · Triphenylene
2-Methoxy-o-terphenyl (2i): Using the general procedure
GP-5, compound 3i (400 mg, 1.3 mmol) and PTSA (67.2 mg,
0.39 mmol) provided compound 2i (284 mg, 84%) as a colorless
oil; 1H NMR (400 MHz, CDCl3): 7.42-7.37 (4H, m), 7.19-7.12 (6H,
m), 6.91 (1H, t, J = 7.4 Hz), 6.69 (1H, d, J = 8.2 Hz), 3.33 (3H,
s); 13C (100 MHz, CDCl3): 142.3, 141.2, 131.7, 131.0, 130.9,
129.8, 129.0, 128.6, 127.7, 127.5, 127.3, 126.3, 120.5, 110.8,
55.0; HRMS (ESI) calcd for C19H17O [M+H]+: 261.1279; Found:
261.1272. o-Terphenyl 2i is previously reported.6a
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Entry for the Table of Contents (Please choose one layout)
Layout 2:
FULL PAPER
RCM Approach to o-Terphenyls*
Shilpi Karmakar, Tirtha Mandal and
Jyotirmayee Dash*
Page No. – Page No.
Title
A synthetic method for o-terphenyls from benzils is reported using ring closing
metathesis (RCM) as the key step. o-Terphenyls with halogen substituents are
synthesized that can be further functionalized by cross coupling reactions. The
synthesis of triphenylenes demonstrates the synthetic utility of the approach.
Ring Closing Metathesis Approach
for the Synthesis of o-Terphenyl
Derivatives
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