New route to o-terphenyls: Application to the synthesis of 6,7,10,11-tetramethoxy-2-(methoxycarbonyl)triphenylene

Article abstract of DOI:10.1039/a707738f

The hydroxy-o-terphenylcarboxylic acid esters 6a-f have been prepared by benzannulation of the 5,6-diaryl-3-methoxycarbonylhexa-3,5-dienoic acids 5a-f using triethylamine-ethyl chloroformate. The application of this new synthesis of triphenylenes is illus

Full text of DOI:10.1039/a707738f

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New route to o-terphenyls: application to the synthesis of
6,7,10,11-tetramethoxy-2-(methoxycarbonyl)triphenylene
Elisabetta Brenna, Claudio Fuganti and Stefano Serra*
Dipartimento di Chimica del Politecnico, Centro CNR per la Chimica delle Sostanze Organiche
Naturali, Via Mancinelli 7, 20133 Milano, Italy
The hydroxy-o-terphenylcarboxylic acid esters 6a–f have been prepared by benzannulation of the
5,6-diaryl-3-methoxycarbonylhexa-3,5-dienoic acids 5a–f using triethylamine–ethyl chloroformate.
The application of this new synthesis of triphenylenes is illustrated through the synthesis of
2-methoxycarbonyl-6,7,10,11-tetramethoxytriphenylene 9.
Introduction
Results and discussion
The chemistry of triphenylenes is receiving current interest
due to the relevant physical properties of these disc-shaped
molecules.1,2 Whereas hexaalkoxytriphenylenes can be easily
obtained through oxidative trimerization of an ortho-dialk-
oxybenzene derivative,3 the preparation of unsymmetrically
substituted derivatives best proceeds from biphenyl4 or
o-terphenyl derivatives,5 respectively, by iron() chloride oxid-
ative coupling. Alternatively, the cyclization can be achieved
by photolysis.6 Moreover, unsymmetrically substituted triphe-
nylenes can be obtained by stepwise palladium-catalyzed cross-
coupling reactions, involving arylboronic acids as intermedi-
ates.7 A major problem in the synthesis of unsymmetrical
triphenylenes through intramolecular C᎐C bond formation is
the obtainment of the o-terphenyls useful as substrates for the
ring closure. Amongst the proposed methods, the Pd0-catalyzed
coupling of arylzinc halides with 1,2-diahalogenobenzenes
seems to be the most effective.5
The synthesis of o-terphenylcarboxylic acid derivatives 6a–g
involves the stepwise construction of the C18–C1 carbon frame-
work of the target molecules from three components, i.e. C6–C1
aromatic aldehydes 1, C6–C2 phenylacetic acids 2 and C4 dime-
thyl succinate, respectively (Scheme 1). Key step in the synthesis
is the benzannulation of the C19 acid 5, bearing two aromatic
rings, through a variation8 of a procedure reported a few years
ago by Ramage and co-workers.9 The cyclization process,
supposedly involving a ketene intermediate, consists of a base-
catalyzed elimination of ethanol and carbon dioxide from the
mixed anhydride formed from ethyl chloroformate and the
carboxylic acid. As in the case of the synthesis of 3-hydroxy
biphenyls and p-terphenyl systems,8 high yields of annulated
products 6 are indeed obtained also in the treatment of the
carboxylic acid 5, in dry tetrahydrofuran (THF) and below
25 ЊC, with ~2 mol equiv. of ethyl chloroformate, followed by
dropwise addition of 3 mol equiv. of triethylamine.
In this context we report now on a novel, flexible approach to
3-hydroxy-4,5-diphenylbenzoic acid esters and on the obtain-
ment, from one of the materials prepared by these means, of
6,7,10,11-tetramethoxy-2-methoxycarbonyltriphenylene 9. The
present synthetic method is compatible with the presence, in the
B and C rings, of a variety of substituents.
A further advantage of the present synthesis of o-terphenyl
derivatives is represented by the simple preparation of the sub-
strates. Indeed, products 5a–g are obtained through
unexceptional steps from commercially available products. First,
C
15 α-arylcinnamic acids 3a–g are obtained by Perkin condens-
ation10 of benzaldehydes 1 with phenylacetic acids 2. Sub-
O
CO2H
R′
R′
Et3N,
Ac2O
ClCO2Et
MnO2
CHCl3
H
R
R
R
R
Et3N, NaBH4
CO2H
CHO
1
2
3
4
CO2Me
CO2H
Benzene
CO2Et
Method Method
CO2Me,
NaOMe
Ph3P
A
B
HO
CO2R′′
R′
a; R = R′ = H, R′′ = Me
b; R = p-Me, R′ = H, R′′ = Me
c; R = p-OMe, R′ = H, R′′ = Me
d; R = H, R′ = p-OMe, R′′ = Me
e; R = p-CN, R′ = p-Cl, R′′ = Et
f; R = R′ = 3,4-(OMe)2, R′′ = Me
g; R = o-NO2, R′ = H, R′′ = Et
NaOH
MeOH
ClCO2Et
Et3N, THF
R
R
CO2R′′
R′
HO2C
6
5
Scheme 1
J. Chem. Soc., Perkin Trans. 1, 1998
901

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sequently, the C15 carboxylic acids are converted into the corres-
ponding aldehydes 4a–g in two steps. The corresponding
alcohols are first prepared upon reduction, with NaBH4, of the
mixed anhydride formed by treatment of the acids in THF with
ethyl chloroformate–Et3N.11 Subsequently, the alcohols are
converted into the aldehydes upon MnO2 oxidation. The C15
aldehydes obtained by these means are homologated to the
desired C19 acids 5a–d, 5f, by Stobbe condensation (Method
A).12 In the case of the aldehydes 4e, 4g, bearing base-sensitive
substituent(s), homologation to the acids 5e, 5g is achieved
by reaction with [β-carboxy-α-(ethoxycarbonyl)ethyl]triphenyl-
phosphonium betaine13 (Method B) in ~50% yield, comparable
with those observed in the other instances under the Stobbe
conditions.
cedure via activation of the carboxy group of β-methoxy-
carbonyl-β,δ-dienic acids by formation of the mixed anhydride
with ethyl chloroformate, followed by triethylamine treatment.8
By this procedure a whole set of 3-hydroxy-4,5-aryl-substituted
benzoic acid esters become accessible. The conditions of the
synthesis are compatible with the presence, in the aromatic B
and C rings, of a variety of functionalities. The hydroxy group
necessarily formed in position 3 of the annulated products
can be reductively removed, thus widening the scope of the
synthesis. The claimed utility of the proposed new access to
o-terphenyls in the chemistry of triphenylenes is now demon-
strated only by the conversion of the o-terphenyl 8f into
triphenylene product 9, but the results of ongoing experiments
The benzannulation of the acids 5a–g to the o-terphenyl
derivatives 6a–g proceeds, under the conditions mentioned
above, in ~80–90% isolated yield. The utility of this new entry
to o-terphenyls in the synthesis of unsymmetrically substituted
triphenylene derivatives is demonstrated by the following
experiments. The esters 6a and 6f are deoxygenated to products
8a and 8f, respectively, upon treatment of the corresponding 5-
phenyltetrazolyl derivatives14 with NaBH4 in the presence of
NiCl2ؒ6H2O in methanol (Scheme 2). We had to rely on this
CO2R′′
MeO
MeO
OMe
OMe
8f
FeCl3, CH2Cl2 cat. H2SO4
HO
CO2R′′
CO2R′′
R
MeO
R′
MeO
6
OMe
5-Cl-1-Ph-1H-tetrazole K2CO3, acetone
OMe
9
N
N
N
on the synthesis of a whole set of unsymmetrically substituted
triphenylenes from o-terphenyls produced by this method will
be presented in due course.
N
O
CO2R′′
Ph
R
Experimental
Mps were measured on a Reichert melting point apparatus,
equipped with a Reichert microscope and are uncorrected. IR
spectra were measured on a Perkin Elmer 2000 FTIR spec-
R′
7
1
trometer. H NMR spectra were recorded in CDCl3 solutions
NiCl2•6H2O MeOH, NaBH4
at room temp. unless otherwise stated, on a Bruker AC-250
1
spectrometer (250 MHz H). The chemical-shift scale is based
CO2R′′
on internal tetramethylsilane. J-Values are given in Hz. Mass
spectra were measured on a FINNIGAN–MAT TSQ 70 spec-
trometer. TLC analyses were performed on Merck Kieselgel
60 F254 plates.
R
R′
General procedure for aldehyde 4
Ethyl chloroformate (15.9 g, 0.147 mol) was added to a solution
of acid 3a (30 g, 0.134 mol) in THF (200 ml) at 0 ЊC. Then a
solution of triethylamine (14.8 g, 0.147 mol) in THF (30 ml)
was dropped and the mixture was stirred for 30 min. The pre-
cipitate (triethylammonium chloride) was filtered off, and
washed with THF (50 ml). The combined filtrate and washings
were then added in a few portions to aq. NaBH4 (12.7 g, 0.335
mol in 100 ml), while the reaction mixture was kept below
20 ЊC. After 15 min, diethyl ether (250 ml) and 5% HCl (200 ml)
were added; the organic phase was separated, dried over
sodium sulfate, and concentrated under reduced pressure. The
crude alcohol was dissolved in CHCl3 (150 ml), treated with
MnO2 (58 g, 0.67 mol), and the mixture was heated under reflux
for 5 h. Filtration and evaporation of the mixture provided an
oil, which was crystallized from ethanol to give pure aldehyde
4a (17 g, 61%).
8
Scheme 2
new method for the cleavage of the oxygen–carbon bond of the
phenyltetrazolyl derivatives at position 3 of the above 4,5-aryl-
substituted benzoate esters, since catalytic hydrogenation failed
under the experimental conditions found to be effective in the
removal of the oxygen functionality in positions ‘out of the
bay’ of triphenylene systems.15 Finally, the ester 8f, bearing
oxygen-substituted aromatic rings, was cleanly converted
into the desired triphenylene derivative 9 by iron() chloride
oxidation.5 The photochemical cyclization of unsubstituted
terphenylcarboxylate 8a to the methyl ester of triphenylene-2-
carboxylic acid is under study.
Thus, these experiments demonstrate the utility in the syn-
thesis of o-terphenyl derivatives of the benzannulation pro-
902
J. Chem. Soc., Perkin Trans. 1, 1998

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᎐
Procedure for method A
and 2228 (C᎐N); δ 1.30 (t, J 7, 3 H, CO CH Me), 3.23 (s, 2 H,
᎐
H 2 2
1-Methyl hydrogen 2-(2,3-diphenylprop-2-enylidene)succinate
5a. A 2.0  solution of sodium methylate (34.5 ml, 68.8 mmol)
in methanol was added to a mixture of aldehyde 4a (13 g, 62.5
mmol) and dimethyl succinate (10 g, 68.8 mmol). The homo-
geneous solution was concentrated under reduced pressure in
30 min at 40 ЊC. The residue was treated with 5% HCl (100 ml)
and extracted with diethyl ether (200 ml). The organic phase
was dried over sodium sulfate and concentrated under reduced
pressure to give a crude product, which was crystallized from
diisopropyl ether as a solid (11 g, 54%), mp 136–137 ЊC
(Found: C, 74.46; H, 5.65. C20H18O4 requires C, 74.52; H,
5.63%); νmax(Nujol)/cmϪ1 1610, 1712 (CO2Me); δH 3.1 (s, 2 H,
CH2CO2H), 3.8 (s, 3 H, OMe), 6.9–7.4 (3 m, 11 H, CHC-
CO2Me ϩ 10 × ArH) and 7.68 (s, 1 H, ArCHCAr); m/z (EI)
322 (Mϩ, 100%), 305 (Mϩ Ϫ OH, 11), 290 (Mϩ Ϫ MeOH, 18),
276 (15), 262 (25), 215 (93), 202 (64), 189 (41) and 165 (17).
1-Methyl hydrogen 2-[3-(4-methylphenyl)-2-phenylprop-2-
enylidene]succinate 5b. Yield 51%; solid, mp 105–107 ЊC
(Found: C, 75.08; H, 5.97. C21H20O4 requires C, 74.98; H,
5.99%); νmax(Nujol)/cmϪ1 1582, 1600 and 1710 (CO2Me); δH
2.25 (s, 3 H, ArMe), 3.06 (s, 2 H, CH2CO2H), 3.78 (s, 3 H,
CO2Me), 6.8–7.4 (m, 10 H, CHCCO2Me ϩ 9 × ArH) and 7.68
CH2CO2H), 4.25 (q, J 7, 2 H, CO2CH2Me), 6.85–7.50 (m, 9 H,
CHCCO2Me ϩ 8 × ArH) and 7.60 (s, 1 H, ArCHCAr); m/z
(EI) 395 (Mϩ, 19%), 349 (Mϩ Ϫ EtOH, 22), 321
(Mϩ Ϫ HCO2Et, 40), 277 (76), 240 (100), 227 (57), 201 (26), 183
(24), 139 (29) and 116 (44).
1-Ethyl
hydrogen
2-[3-(2-nitrophenyl)-2-phenylprop-2-
enylidene]succinate 5g. Yield 53%; amorphous solid obtained as
a pure compound by column chromatography with hexane–
ethyl acetate (2:1–1:1) as eluent (Found: C, 66.01; H, 4.97; N,
3.73. C21H19NO6 requires C, 66.14; H, 5.02; N, 3.67%);
νmax(Nujol)/cmϪ1 1527 and 1712 (CO2Et); δH 1.3 (t, J 7.2, 3 H,
CO2CH2Me), 3.36 (s, 2 H, CH2CO2H), 4.37 (q, J 7.2, 2 H,
CO2CH2Me), 6.90–7.30 (m, 8 H, 7 × ArH ϩ ArCHCO2Et),
7.70 (s, 1 H, ArCHCAr) and 7.99 (m, 1 H, ArH); m/z (EI) 381
(Mϩ, 9%), 353 (Mϩ Ϫ CO, 20), 279 (18), 246 (58), 217 (40), 155
(27), 149 (100), 141 (64), 105 (60), 99 (68) and 91 (61).
Procedure for the cyclization
3Ј-Hydroxy-5Ј-methoxycarbonyl-1,1Ј:2Ј,1Љ-terphenyl
6a.
Ethyl chloroformate (6.65 g, 61.5 mmol) was added to a solu-
tion of the monoacid monoester 5a (9 g, 28 mmol) in dry THF
(80 ml); then, triethylamine (8.5 g, 84 mmol) was added drop-
wise, with the temperature kept under 25 ЊC. The reaction
mixture was stirred for 15 min, then was treated with 5% HCl
(80 ml) and extracted with diethyl ether. The organic phase
was concentrated under reduced pressure and the residue was
stirred at room temp. with NaOH (2 g, 50 mmol) in methanol
for 10 min. The mixture was treated with 5% HCl (100 ml),
extracted with diethyl ether, and the organic phase was concen-
trated under reduced pressure. The residue was crystallized
from diisopropyl ether to give the phenol derivative 6a (7.1 g,
83%) as a solid, mp 155–157 ЊC (Found: C, 79.01; H, 5.35.
C20H16O3 requires C, 78.93; H, 5.30%); νmax(Nujol)/cmϪ1 1565,
1706 (CO2Me) and 3463 (OH); δH 3.92 (s, 3 H, CO2Me), 5.40
(br s, 1 H, OH), 7.0–7.4 (m, 10 H, 10 × ArH) and 7.70 (br s, 2
H, 2 × ArH); m/z (EI) 304 (Mϩ, 48%), 273 (Mϩ Ϫ OMe, 87),
245 (Mϩ Ϫ CO2Me, 92), 227 (Mϩ Ϫ Ph, 81), 215 (100), 202 (93),
189 (67), 139 (42) and 115 (13).
(s,
1
H, ArCHCAr); m/z (EI) 336 (Mϩ, 23%), 304
(Mϩ Ϫ MeOH, 7), 276 (Mϩ Ϫ HCO2Me, 43), 258 (25), 245 (36),
231 (100), 215 (76), 202 (33) and 115 (41).
1-Methyl hydrogen 2-[3-(4-methoxyphenyl)-2-phenylprop-2-
enylidene]succinate 5c. Yield 56%; solid, mp 125–126 ЊC
(Found: C, 71.70; H, 5.66. C21H20O5 requires C, 71.58; H,
5.72%); νmax(Nujol)/cmϪ1 1583, 1600 and 1703 (CO2Me); δH
3.02 (s, 2 H, CH2CO2H), 3.73 (s, 3 H, OMe), 3.79 (s, 3 H,
CO2Me), 6.6–7.4 (m, 10 H, CHCCO2Me ϩ 9 × ArH) and 7.65
(s, 1 H, ArCHCAr); m/z (EI) 352 (Mϩ, 61%), 321 (Mϩ Ϫ OMe,
6), 292 (Mϩ Ϫ HCO2Me, 67), 261 (38), 247 (100), 233 (31), 202
(49), 189 (27), 165 (37) and 121 (46).
1-Methyl hydrogen 2-[2-(4-methoxyphenyl)-3-phenylprop-2-
enylidene]succinate 5d. Yield 60%; amorphous solid obtained as
a pure compound by column chromatography with hexane–
ethyl acetate (3:1–1:1) as eluent (Found: C, 71.74; H, 5.72%);
νmax(Nujol)/cmϪ1 1610 and 1699 (CO2Me); δH 3.15 (s, 2 H,
CH2CO2H), 3.76 (s, 3 H, OMe), 3.81 (s, 3 H, CO2Me), 6.8–7.2
(m, 10 H, CHCCO2Me ϩ 9 × ArH) and 7.66 (s, 1 H, ArCH-
CAr); m/z (EI) 353 (Mϩ ϩ 1, 52%), 352 (Mϩ, 100), 320
(Mϩ Ϫ MeOH, 25), 292 (Mϩ Ϫ HCO2Me, 88), 261 (51), 247
(98), 233 (56), 215 (69), 189 (43), 165 (57) and 135 (40).
1-Methyl hydrogen 2-[2,3-bis-(3,4-dimethoxyphenyl)prop-2-
enylidene]succinate 5f. Yield 66%; solid, mp 125–126 ЊC (from
AcOEt) (Found: C, 65.04; H, 5.87. C24H26O8 requires C, 65.15;
H, 5.92%); νmax(Nujol)/cmϪ1 1587, 1620, 1690 and 1715; δH 3.08
(s, 2 H, CH2CO2H), 3.47 (s, 3 H, CO2Me), 3.76 (s, 3 H, OMe),
3.80 (s, 3 H, OMe), 3.83 (s, 3 H, OMe), 3.89 (s, 3 H, OMe), 6.43
(s, 1 H, CHCCO2Me), 6.65–6.95 (m, 6 H, 6 × ArH) and 7.68 (s,
1 H, ArCHCAr); m/z (EI) 442 (Mϩ, 100%), 410 (Mϩ Ϫ MeOH,
10), 382 (Mϩ Ϫ HCO2Me, 41), 337 (63), 323 (38), 306 (35), 292
(29) and 151 (46).
3Ј-Hydroxy-5Ј-methoxycarbonyl-4Љ-methyl-1,1Ј:2Ј,1Љ-
terphenyl 6b. Yield 94%; a solid, mp 211–212 ЊC (Found: C,
79.11; H, 5.66. C21H18O3 requires C, 79.23; H, 5.70%);
νmax(Nujol)/cmϪ1 1585, 1698 (CO2Me) and 3434 (OH); δH 2.32
(s, 3 H, ArMe), 3.90 (s, 3 H, CO2Me), 4.80 (br s, 1 H, OH),
7.00–7.20 (m, 9 H, 9 × ArH) and 7.68 (m, 2 H, 2 × ArH); m/z
(EI) 319 (Mϩ ϩ 1, 20%), 318 (Mϩ, 100), 303 (Mϩ Ϫ Me, 18), 287
(Mϩ Ϫ OMe, 23), 259 (Mϩ Ϫ CO2Me, 19), 226 (16), 215 (41),
202 (15), 189 (18), 139 (13) and 115 (12).
3Ј-Hydroxy-4Љ-methoxy-5Ј-methoxycarbonyl-1,1Ј:2Ј,1Љ-
terphenyl 6c. Yield 88%; a solid, mp 208–209 ЊC (Found: C,
75.61; H, 5.35. C21H18O4 requires C, 75.43; H, 5.43%);
νmax(Nujol)/cmϪ1 1609, 1694 (CO2Me) and 3436 (OH); δH 3.78
(s, 3 H, OMe), 3.92 (s, 3 H, CO2Me), 5.34 (s, 1 H), 6.8–7.2 (m, 9
H, 9 × ArH) and 7.67 (m, 2 H, 2 × ArH); m/z (EI) 334 (Mϩ,
39%), 303 (Mϩ Ϫ OMe, 9), 301 (10), 275 (Mϩ Ϫ CO2Me, 94),
215 (38), 202 (100), 189 (29), 176 (21) and 152 (12).
Procedure for method B
3Ј-Hydroxy-4-methoxy-5Ј-methoxycarbonyl-1,1Ј:2Ј,1Љ-
1-Ethyl hydrogen 2-[2-(4-chlorophenyl)-3-(4-cyanophenyl)-
prop-2-enylidene]succinate 5e. [β-Carboxy-α-(ethoxycarbonyl)-
ethyl]triphenylphosphonium betaine (4.05 g, 10 mmol) was
added in one portion to a solution of aldehyde 4e (2.1 g, 8
mmol) in dry benzene (20 ml). After stirring of the mixture at
40 ЊC for 48 h, the reaction mixture was treated with water (40
ml) and extracted with ethyl acetate (100 ml). The organic phase
was dried over sodium sulfate and concentrated under reduced
pressure. The residue was chromatographed on a silica gel col-
umn and eluted with hexane–ethyl acetate (5:1–1:1) to give the
monoester monoacid 5e (1.8 g, 56%) as an oil (Found: C, 66.84;
H, 4.63; Cl, 8.79; N, 3.67. C22H18ClNO4 requires C, 66.75; H,
4.58; Cl, 8.96; N, 3.54%); νmax(Nujol)/cmϪ1 1600, 1710 (CO2Et)
terphenyl 6d. Yield 81%; a solid, mp 158–159 ЊC (Found: C,
75.38; H, 5.51%); νmax(Nujol)/cmϪ1 1609, 1690 (CO2Me) and
3374 (OH); δH 3.78 (s, 3 H, OMe), 3.93 (s, 3 H, CO2Me),
5.3 (s, 1 H, OH), 6.60–7.05 (m, 4 H, 4 × ArH p-substituted),
7.10–7.40 (m, 5 H, 5 × ArH) and 7.66 (m, 2 H, 2 × ArH); m/z
(EI) 334 (Mϩ, 36%), 303 (Mϩ Ϫ OMe, 12), 301 (10), 275
(Mϩ Ϫ CO2Me, 60), 242 (34), 213 (76), 202 (100), 189 (28), 176
(21) and 152 (14).
4-Chloro-4Љ-cyano-5Ј-ethoxycarbonyl-3Ј-hydroxy-1,1Ј:2Ј,1Љ-
terphenyl 6e. Yield 77%; a solid, mp 164–165 ЊC (Found: C,
70.10; H, 4.31; Cl, 9.21; N, 3.59. C22H16ClNO3 requires C,
69.94; H, 4.27; Cl, 9.38; N, 3.71%); νmax(Nujol)/cmϪ1 1610, 1719
᎐
(CO Et), 2236 (C᎐N) and 3341 (OH); δ 1.40 (t, J 7.5, 3 H,
᎐
2
H
J. Chem. Soc., Perkin Trans. 1, 1998
903

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CO2CH2Me), 4.40 (q, J 7.5, 2 H, CO2CH2Me), 5.56 (br s, 1 H)
and 6.90–7.70 (m, 10 H, 10 × ArH); m/z (EI) 379 (Mϩ ϩ 2,
21%), 377 (Mϩ, 62), 332 (Mϩ Ϫ OEt, 44), 304 (Mϩ Ϫ CO2Et, 8),
269 (61), 240 (100), 213 (23), 201 (13) and 187 (8).
(s, 3 H, OMe), 3.62 (s, 3 H, OMe), 3.86 (br s, 6 H, 2 × OMe),
3.95 (s, 3 H, CO2Me), 6.55–6.85 (m, 6 H, 6 × ArH) and 7.9–8.1
(m, 3 H, ArH); m/z (EI) 408 (Mϩ, 52%), 376 (Mϩ Ϫ MeOH, 7),
349 (Mϩ Ϫ CO2Me, 100), 318 (24), 202 (30) and 189 (54).
3Ј-Hydroxy-3,3Љ,4,4Љ-tetramethoxy-5Ј-methoxycarbonyl-
1,1Ј:2Ј,1Љ-terphenyl 6f. Yield 84%; a solid, mp 175–176 ЊC (from
AcOEt) (Found: C, 68.04; H, 5.63. C24H24O7 requires C, 67.92;
H, 5.70%); νmax(Nujol)/cmϪ1 1702 (CO2Me) and 3425 (OH); δH
3.60 (s, 3 H, OMe), 3.65 (s, 3 H, OMe), 3.85 (s, 3 H, OMe), 3.88
(s, 3 H, OMe), 3.96 (s, 3 H, CO2Me), 4.75 (br s, 1 H, OH), 6.5–
6.9 (m, 6 H, 6 × ArH) and 7.63–7.72 (m, 2 H, 2 × ArH); m/z
(EI) 424 (Mϩ, 100%), 393 (Mϩ Ϫ OMe, 8), 377 (11), 247 (5), 189
(10) and 91 (18).
5Ј-Ethoxycarbonyl-3Ј-hydroxy-2Љ-nitro-1,1Ј:2Ј,1Љ-terphenyl
6g. Yield 78%; amorphous solid obtained as a pure compound
by column chromatography and elution with hexane–ethyl
acetate (3:1–2:1) (Found: C, 69.28; H, 4.66; N, 3.75.
C21H17NO5 requires C, 69.41; H, 4.72; N, 3.85%); νmax(Nujol)/
cmϪ1 1708 (CO2Et) and 3380 (OH); δH 1.35 (t, J 6.7, 3 H,
CO2CH2Me), 4.40 (q, J 6.7, 2 H, CO2CH2Me), 6.90–7.40 (m, 8
H, 8 × ArH), 7.63 (d, J 1.5, 1 H, ArH), 7.72 (d, J 1.5, 1 H, ArH)
and 7.92–8.00 (m, 1 H, ArH); m/z (EI) 363 (Mϩ, 100%), 318
(Mϩ Ϫ OEt, 47), 274 (34), 246 (62), 215 (69), 119 (67), 105 (81)
and 77 (36).
Preparation of the triphenylene
Methyl 6,7,10,11-tetramethoxytriphenylene-2-carboxylate 9.
The o-terphenyl 8f (0.9 g, 2.2 mmol) as a solution in CH2Cl2 (5
ml) was added dropwise at room temp. to a stirred solution of
FeCl3 (1.1 g, 6.7 mmol) in CH2Cl2 (20 ml). A catalytic quantity
(few mg) of conc. H2SO4 was added and the stirring was con-
tinued for 15 min; then the mixture was quenched with MeOH
(5 ml), diluted with diethyl ether (80 ml), and washed with water
(80 ml). The organic phase was dried over sodium sulfate, and
concentrated under reduced pressure. The residue was chroma-
tographed on a silica gel column, and eluted with hexane–ethyl
acetate (2:1–1:3), to give derivative 9 (0.5 g, 56%) as an
amorphous solid (Found: C, 70.86; H, 5.40. C24H22O6 requires
C, 70.93; H, 5.46%); νmax(Nujol)/cmϪ1 1518, 1614 and 1720
(CO2Me); δH 4.05 (s, 3 H, CO2Me), 4.12 (s, 9 H, 3 × OMe), 4.14
(s, 3 H, OMe), 7.65 (br s, 2 H, 2 × ArH), 7.86 (s, 1 H, ArH), 7.93
(s, 1 H, ArH), 8.15 (d, J 8, 1 H, ArH), 8.42 (d, J 8, 1 H, ArH)
and 9.10 (s, 1 H, ArH); m/z (EI) 406 (Mϩ, 100%), 363 (18), 348
(10), 304 (17), 203 (22) and 188 (19).
Procedure for deoxygenation of derivative 6
References
4Ј-Methoxycarbonyl-1,1Ј:2Ј,1Љ-terphenyl 8a. A mixture of
compound 6a (2 g, 6.6 mmol), potassium carbonate (4.8 g, 33
mmol), and 5-chloro-1-phenyl-1H-tetrazole (1.8 g, 10 mmol) in
acetone (80 ml) was refluxed for 12 h. The solvent was removed
under reduced pressure; the residue was treated with water (100
ml), and extracted with methylene dichloride. The organic
phase was dried over sodium sulfate and concentrated under
reduced pressure. The residue was chromatographed on a silica
gel column, with hexane–ethyl acetate (2:1) as eluent, to give
derivative 7a (2.8 g, 94%).
This derivative was added to a solution of NiCl2ؒ6H2O (7.8 g,
33 mmol) in methanol (100 ml) and the mixture was stirred
until it became homogeneous. The resulting solution was
cooled at 0 ЊC and NaBH4 (0.75 g, 20 mmol) in methanol (20
ml) was added dropwise. After being stirred for 30 min the
black mixture was treated with 1% HCl (100 ml) and extracted
with diethyl ether (150 ml). The organic phase was dried over
sodium sulfate and concentrated under reduced pressure. The
residue was chromatographed on a silica gel column, and eluted
with hexane–acetate (9:1), to give recovered intermediate 7a
(1.0 g) and the o-terphenyl 8a as an oil (0.93 g, 51%) (Found: C,
83.47; H, 5.51. C20H16O2 requires C, 83.31; H, 5.59%);
νmax(film)/cmϪ1 1600 and 1721 (CO2Me); δH 3.93 (s, 3 H,
CO2Me), 7.05–7.3 (m, 11 H) and 8.04–8.12 (m, 2 H); m/z (EI)
288 (Mϩ, 100%), 274 (15), 257 (Mϩ Ϫ OMe, 43), 229
(Mϩ Ϫ CO2Me, 65), 202 (24), 165 (8), 152 (11), 128 (9) and 113
(13).
1 N. Boden, R. J. Bushby and A. N. Cammidge, J. Am. Chem. Soc.,
1995, 117, 924.
2 W. Kreuder and H. Ringsdorf, Makromol. Chem. Rapid Commun.,
1983, 4, 807; W. Kreuder, H. Ringsdorf and P. Tschirner, Makromol.
Chem. Rapid Commun., 1985, 6, 367.
3 I. M. Matheson, O. C. Musgrave and C. J. Webster, Chem. Commun.,
1965, 278; N. Boden, R. C. Borner, R. J. Bushby, A. N. Cammidge
and M. V. Jesudason, Liq. Cryst., 1993, 15, 851.
4 N. Boden, R. J. Bushby and A. N. Cammidge, J. Chem. Soc., Chem.
Commun., 1994, 465.
5 R. C. Borner and R. F. W. Jackson, J. Chem. Soc., Chem. Commun.,
1984, 845; G. Wenz, Makromol. Chem. Rapid Commun., 1985,
6, 577.
6 R. J. Bushby and C. Hardy, J. Chem. Soc., Perkin Trans. 1, 1986,
721.
7 G. W. Gray, M. Hird, D. Lacey and K. J. Toyne, J. Chem. Soc.,
Perkin Trans. 2, 1989, 2041; J. W. Goodby, M. Hird, K. J. Toyne and
T. Watson, J. Chem. Soc., Chem. Commun., 1994, 1701.
8 E. Brenna, C. Fuganti, V. Perozzo and S. Serra, Tetrahedron, 1997,
53, 15 029.
9 K. Clinch, C. J. Marquez, M. J. Parrott and R. Ramage,
Tetrahedron, 1989, 45, 239.
10 J. R. Johnson, Org. React., 1942, 1, 220.
11 K. Ishizumi, K. Koga and S. I. Yamada, Chem. Pharm. Bull., 1968,
16, 492.
12 W. S. Johnson and G. H. Daub, Org. React., 1951, 6, 2.
13 R. F. Hudson and P. A. Chopard, Helv. Chim. Acta, 1963, 46, 2179.
14 W. J. Musliner and J. W. Gates Jr., J. Am. Chem. Soc., 1966, 88, 4271.
15 P. Henderson, S. Kumar, J. A. Rego, H. Ringsdorf and
P. Schumacher, J. Chem. Soc., Chem. Commun., 1995, 1059.
3,3Љ,4,4Љ-Tetramethoxy-4Ј-methoxycarbonyl-1,1Ј:2Ј,1Љ-
terphenyl 8f. Yield 55%; an oil obtained as a pure compound by
column chromatography with hexane–ethyl acetate (2:1–1:1)
as eluent (Found: C, 70.79; H, 6.01. C24H24O6 requires C, 70.58;
H, 5.92%); νmax(film)/cmϪ1 1600 and 1716 (CO2Me); δH 3.60
Paper 7/07738F
Received 27th October 1997
Accepted 18th December 1997
904
J. Chem. Soc., Perkin Trans. 1, 1998