Formation of arenes via diallylarenes: Strategic utilization of Suzuki-Miyaura cross-coupling, Claisen rearrangement and ring-closing metathesis

Article abstract of DOI:10.1002/adsc.200600469

Two new synthetic strategies for benzoannulation are reported. The first strategy is based on the Suzuki-Miyaura cross-coupling reaction. To this end, various ortho-diallylbenzene derivatives were prepared from the corrresponding diiodo derivatives by an allylation strategy using an allylboronate as coupling partner. These diallyl derivatives were subjected to a ring-closing metathesis (RCM) and one-pot dichlorodicyanoquinone (DDQ) oxidation sequence to deliver 2-substituted naphthalenes. In the second strategy, a double Claisen rearrangement and RCM protocol have been used as key steps to give highly functionalized benzoannulated quinone derivatives.

Full text of DOI:10.1002/adsc.200600469

FULL PAPERS
DOI: 10.1002/adsc.200600469
Formation of Arenes via Diallylarenes: Strategic Utilization of
Suzuki–Miyaura Cross-Coupling, Claisen Rearrangement and
Ring-Closing Metathesis
Sambasivarao Kotha,a,* Vrajesh R. Shah,a and Kalyaneswar Mandala
a
Department of Chemistry, Indian Institute of Technology – Bombay, Powai, Mumbai – 400076, India
Fax : (+91)-22-2572-3480; phone: (+91)-22-2576-7160; e-mail: srk@chem.iitb.ac.in
Received: September 12, 2006
Abstract: Two new synthetic strategies for benzoan- quence to deliver 2-substituted naphthalenes. In the
nulation are reported. The first strategy is based on second strategy, a double Claisen rearrangement and
the Suzuki–Miyaura cross-coupling reaction. To this RCM protocol have been used as key steps to give
end, various ortho-diallylbenzene derivatives were highly functionalized benzoannulated quinone deriv-
prepared from the corrresponding diiodo derivatives atives.
by an allylation strategy using an allylboronate as
coupling partner. These diallyl derivatives were sub- Keywords: benzoannulation; Claisen rearrangement;
jected to a ring-closing metathesis (RCM) and one- diallylarenes; 2-naphthalene derivatives; ring-closing
pot dichlorodicyanoquinone (DDQ) oxidation se- metathesis; Suzuki–Miyaura cross-coupling
Introduction
As part of a major program involving metathesis
sequences, two new strategies for benzoannulation in-
Functionalized aromatics are found to be useful build- volving RCM as a key step were conceived. Both of
ing blocks in organic synthesis and medicinal chemis- these strategies rely on common types of intermedi-
try. Generally they are accessible by functional group ates involving diallylarenes (Figure 1). In the first ap-
manipulation of preformed aromatic derivatives.
These strategies provide aromatics with limited substi-
tution patterns. To this end, the benzoannulation reac-
tion, a single or multi-step process which involves ap-
pending an aromatic ring starting with readily avail-
able substrates seems to be a useful strategy to afford
highly functionalized aromatics. Various biologically
active quinones or naphthalene derivatives have
become easily available because of the advancement
of such reactions. A variety of synthetic methodolo-
gies have been reported for benzoannulation starting
with acyclic or cyclic precursors.[1] Recently reported,
Pd-catalyzed benzoannulation strategies furnish di-
Figure 1.
verse polysubstituted aromatics. In this respect, Ya-
mamotoꢀs group reported the [4+2]-benzoannulation proach, diallylarenes are derived by application of the
of enyne-ynes to give 1,4- or 1,2,4-substituted benzene Suzuki–Miyaura (SM) cross-coupling[6] with o-substi-
derivatives[2] while Takahashi and co-workers dis- tuted dihalo aromatics. In the second strategy, a
closed the coupling of o-diiodoarene with alkynes to double Claisen rearrangement generated the quinone-
give tetrasubstituted naphthalene derivatives in mod- based diallylarenes.[7] Subsequently, these diallylar-
erate to good yields.[3] The Dçtz annulation provides enes on reaction with Grubbsꢀ ruthenium-based re-
a unique class of quinone derivatives with additional agent generate ring-closing products which, on DDQ
functionality.[4] Surprisingly, a benzoannulation strat- or MnO2 oxidation, gave the benzoannulated prod-
egy based on ring-closing metathesis (RCM) is rela- ucts. Here, the full details of these strategies are dis-
tively less explored.[5]
closed.
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Results and Discussion
In recent times, RCM involving the ruthenium cata-
lysts 1 and 2 (Figure 2) has become a useful tool for
Scheme 2.
Having prepared several diiodo derivatives, the
stage was set for the SM cross-coupling reaction.
When the 3,4-diiodonitrobenzene 6 was subjected to
the SM cross-coupling reaction with allylboronate 3,
3,4-diallylnitrobenzene 7 was isolated in 90% yield
Figure 2.
synthetic chemists and has found various applications (Scheme 3). The diallyl derivative 7 was characterized
for the preparation of diverse heterocyclic, carbocy- by its complementary spectral (1H NMR, 13C NMR
clic and macrocyclic molecules.[8] Earlier we have and mass) data.
demonstrated a simple protocol for the allylation of
aromatic halides via the SM cross-coupling reaction
using the allylboronate 3 as a coupling partner
(Scheme 1).[9] As an extension of this methodology,
extrapolation of the diallylation protocol with aromat-
ic substrates can give useful precursors suitable for
the benzoannulation strategy.
Scheme 3.
Next, the diallylnitrobenzene 7 was treated with the
Grubbsꢀ catalyst 1 (3 mol%) in dry dichloromethane
at room temperature (Scheme 3) and the reaction was
Scheme 1.
completed after 20 min. The dihydronaphthalene de-
rivative 8 was isolated in 92% yield and its structure
In this regard, it was found that 1,2-diallylbenzene was confirmed on the basis of routine spectral data.
derivatives can be prepared by diallylation of the cor-
Then, the dihydronaphthalene derivative 8 was sub-
responding diiodo derivatives via SM cross-coupling jected to DDQ oxidation in refluxing benzene. Here,
with allylboronate 3. Since aromatic iodides with the monitoring of the reaction with the aid of TLC ap-
electron-withdrawing groups gave good yields of the pears to be difficult as the RCM product and the ar-
cross-coupling products, the preparation of various o- omatized product have the same Rf value. So the oxi-
diiodobenzene derivatives was undertaken.
dation reaction was continued for an extended period
The required 1,2-diiodo derivatives were prepared (ca. 48 h) to ensure the completion of the reaction
by adopting a tactical combination of the existing lit- and the dehydrogenated product, 2-nitronaphthalene
erature methods.[10] For example, 2-iodoaniline deriva- 9 was isolated in 60% yield (Scheme 4).
tives on diazotization followed by treatment with
Having demonstrated the benzoannulation strategy
aqueous potassium iodide gave various 1,2-diiodoben- with the first substrate, our attention was directed to-
zene derivatives. In another series, KI/KIO3/HCl con- wards the generalization of this strategy. Various sub-
ditions were employed as a source of iodine which ex-
clusively gave the 2-iodo-4-nitroaniline 5 in 95%
yield when using 4-nitroaniline 4 as starting material.
Diazotization of the 2-iodoaniline derivative 5 with
sodium nitrite in HCl/H2O (1:1), followed by treat-
ment with aqueous potassium iodide gave 3,4-diiodo-
nitrobenzene 6 in 84% yield (Scheme 2).
Scheme 4.
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strates prepared in this venture are included in complete conversion to RCM product) in benzene
Table 1. The 2-iodoaniline derivatives 10–13, precur- (10 mL). The resulting reaction mixture was heated at
sors of diiodo derivatives, were prepared by adopting reflux temperature for 48 h and the aromatized prod-
a similar protocol as that employed in the preparation uct 22 was isolated in 86% yield (Table 2, entry 2).
of 2-iodo-4-nitroaniline 5. The requisite diiodo deriva- RCM followed by one-pot DDQ oxidation of the dia-
tives were prepared in a moderate to good yield llyl derivatives 19–21 gave the aromatized products
(Table 1) by diazotization of 2-iodoaniline derivatives 23–25 in good yields (Table 2, entries 3–5).
10–13 by adopting standard diazotization conditions
In the second benzoannulation strategy, a sequen-
followed by treatment with aqueous potassium iodide. tial combination of the Claisen rearrangement[12] and
Diazotization of anilines such as 12 and 13 with RCM protocol has been employed for the synthesis of
sodium nitrite in HCl/H2O (1:1), followed by treat- various quinone derivatives. It seems that suitably
ment with aqueous potassium iodide gave unstable functionalized quinones are useful therapeutic com-
products. However, diazotization of compound 12 pounds for the treatment of a wide variety of disor-
under H2SO4/NaNO2 conditions, followed by treat- ders. For example, anthracycline antibiotics[13] such as
ment with aqueous KI afforded the diiodo derivative idarubicin (26), doxorubicin (27) and daunorubicin
[11]
16 in 40% yield (Table 1, entry 4). Surprisingly, the (28) have widely been used as clinically effective anti-
diazotization of compound 13 under similar reaction tumor agents against acute leukemia, Hodgkinꢀs dis-
conditions gave diiodo derivative 17 in 48% yield ease, lymphomas, breast carcinomas and sarcomas
(Table 1, entry 5).
(Figure 3).[14] Additionally, various naphthacenediones
Along similar lines, the diiodo derivatives 14–17 are found to exhibit potent biological activity. More
were subjected to SM cross-coupling conditions and specifically, XR651 (29) is identified as a novel naph-
the corresponding diallyl derivatives 18–21 were iso- thacene-5,12-dione derivative that inhibits interleu-
lated in good to excellent yields (Table 1, entrie 2–5). kin-1 signal transduction in carcinoma cells.[15]
When the diallyl derivative 18 was treated with
The required precursors suitable for double Claisen
Grubbsꢀ catalyst 1, the reaction was completed after rearrangement were prepared via O-allylation of the
20 mins. Unfortunately, the corresponding dihydro de- corresponding 1,4-dihydroxybenzene derivatives by
rivative was found to be unstable. So, it was decided following the conventional allylation conditions using
to oxidize the crude RCM product and, therefore, a allyl bromide, potassium carbonate in acetone at
one-pot RCM and DDQ sequence was planned. Thus, room temperature (Scheme 5). The desired di-olefinic
the diallyl derivative 18 was treated with catalyst 1 in precursors required for the RCM were obtained via
dry dichloromethane and at the conclusion of the re- double Claisen rearrangement of bis-allyloxybenzene
action (20 min, TLC monitoring), the reaction mix- derivatives under different reaction conditions. The
ture was treated with DDQ (2.5 equivalents, based on allyloxyanthraquinone 33 is somewhat resistant to the
Table 1. List of 2-iodoaniline derivatives and diiodo derivatives isolated.
Entry
2-Iodoaniline Derivatives
Yield [%]
Diazotization Method[a]
3,4-Diiodo Derivatives
Yield [%][b]
84
1
5
95
A
6
2
3
10
11
84
95
A
A
14
15
67
68
4
12
13
93
B
B
16
17
40
48
5
70[b]
[a]
A: (i) HCl/H2O, NaNO2; (ii) KI. B: (i) H2SO4, NaNO2; (ii) KI.
Isolated yield after column chromatography.
[b]
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Table 2. List of 3,4-diallyl derivatives and naphthalene derivatives prepared.
Entry
Cross-Coupling Product
Yield [%][a]
Aromatized Product
Yield [%][b]
60[c]
1
7
90
9
2
3
18
19
95
92
22
23
86
82
4
20
21
71
89
24
25
82
82
5
[a]
Isolated yield after column chromatography.
Overall yield after RCM and DDQ oxidation sequence.
Isolated yield of aromatized product of dihydronaphthalene derivative 8 after DDQ oxidation.
[b]
[c]
atives 37 and 39 during purification on a silica gel
column (Scheme 7). This critical observation prompt-
ed the exploration of the Claisen rearrangement on a
silica gel support to obtain a one-pot conversion of
1,4-bis-allyloxybenzene derivatives to 2,3-bis-allyl-1,4-
quinone derivatives.
Figure 3.
thermal Claisen rearrangement. Although one of the
allyl group rearranges under normal conditions, rear-
rangement of the second allyl group is sluggish and
consequently the other possible side reactions are ex-
pected to compete. To circumvent these problems, the
carbonyl groups of the anthraquinone are reduced in
situ to give an anthraquinone radical anion or dianion
under appropriate conditions amenable for Claisen
rearrangement. In this regard, treatment of the bis-al-
lyloxyanthraquinone 33 with sodium dithionite (1.0
mol equiv.) in the presence of sodium hydroxide (4
mol equivs.) in dimethylformamide-water (1:1) with
heating for 1 h furnished the desired doubly rear-
ranged product 36 in good yield (Scheme 6).[16]
Thermal Claisen rearrangement of the 1,4-bis-
ACHTREUNG
ACHTREUNG
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Scheme 6.
In recent years, solvent-free reactions using either
organic or inorganic solid supports have received in-
creasing attention.[17] There are multiple advantages
for executing the synthetic sequence in dry media.
These include: (i) short reaction times, (ii) increased
safety, (iii) economic advantages due to the absence
of solvent. Silica gel is effective because the end prod-
Scheme 8.
ucts can easily be separated. Moreover, silica gel can the aid of TLC at regular intervals. It was found that
function as a convenient medium and act as a mild a prolonged MWI gave an intractable polymeric ma-
acidic catalyst.
terial, thereby reducing the yield of the required
Microwave irradiation (MWI) has become an es- product. To avoid the polymerization problem, the
tablished and popular tool in organic synthesis, be- MWI power level was reduced which, in turn, in-
cause of the rate enhancements, higher yields and creased the total exposure time.
often improved selectivity, with respect to convention-
al reaction conditions.[18] In addition, solvent-free alumina and the highly acidic montmorillonite clay)
MWI processes are also clean and efficient. tested for the Claisen rearrangement, silica gel was
Among the various solid supports (e.g., silica gel,
In view of the several advantages of silica gel-sup- found to be the most efficient medium. Here, the role
ported organic synthesis and MWI under solvent-free of silica gel may be twofold: (i) enhancement of reac-
conditions, compound 34 was heated in an unmodified tion rate due to physisorption of reactants on the
domestic MW oven with a maximum power (800 W) silica surface which, in turn, increases the local con-
on a silica gel support for 7 min to produce the corre- centration of substrate and (ii) the silica surface being
sponding bis-allylated ketone 38. Consequently, a sig- acidic in nature, promotes the autooxidation of
nificant rate enhancement and improved yield of the phenol to the corresponding quinone derivative.[20]
rearranged product was observed under MWI condi-
Having the diallylated derivatives in hand, the
tions on a silica gel support compared to the conven- RCM with compound 36 was attempted. In this con-
tional reaction conditions. It is worth mentioning that, text, Grubbsꢀ catalysts 1 and 2 failed to give the de-
under similar reaction conditions, compound 35 upon sired product, and a complex mixture of products was
irradiation for 15 min gave the aromatized quinone 41 formed as indicated by TLC.
in 43% yield (Scheme 8).[19] The reaction time was
Next, the free hydroxy groups of 36 were protected
optimized by monitoring the individual reaction with (Scheme 9) and these modified tetracyclic derivatives
Scheme 7.
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Scheme 9.
successfully underwent the RCM (without isolation) quinone derivatives. It is worth mentioning that the
and, on aromatization with DDQ, gave a moderate RCM products 45, 46 or 47 are advanced precursors
overall yield of the benzoannulated products (Table 3, for the synthesis of potent anticancer analogues such
entries 1 and 2). Surprisingly, no product formation as idarubicin (26) using simple transformations.
was observed when compound 44 was exposed to the
Grubbsꢀ catalyst 1 which could be attributed to the
complexation of the catalyst with the acetyl group. Experimental Section
The use of the more reactive Grubbsꢀ catalyst 2, how-
ever, afforded the desired product in good yield General Remarks
(Table 3, entry 3). Along similar lines, exposure of
All the commercial grade reagents were used without fur-
compounds 38, 40 and 41 to the Grubbsꢀ catalyst 1
ther purification. Grubbsꢀ catalysts (1 and 2), allylboronate
followed by one-pot aromatization with DDQ afford-
(3), 4-dihydroxyanthraquinone (30), 2,3-dimethylbenzene-
ed compounds 54, 55 and 55, respectively, in good
yields (Table 3, entries 4–6).
1,4-diol (31), 2,3-dimethyl-1,3-butadiene, and methyl iodide
were purchased from Aldrich Chemical Co., Inc. (Milwau-
kee, WI, USA). 4-Aminoacetophenone, sodium dithionite
(Spectrochem), acetic anhydride, ethyl bromide and allyl
bromide (s. d. fine-Chem Limited) were used as received. 4-
Nitroaniline (4) and 4-aminobenzoic acid were commercially
available. 1-Nitronaphthalene was purchased from Alfa
Aesar Ltd. UK. 2-Iodo-4-nitroaniline (5),[10] methyl 4-amino-
benzoate,[24] ethyl 4-aminobenzoate,[26] 4-nitronaphthyl-
amine,[30] 3,4-diiodo-1-nitro naphthalene (16),[11] 1,4-bis-allyl-
Conclusions
We have demonstrated two simple strategies for ben-
zoannulation. The first benzoannulation strategy has
been accomplished via the SM cross-coupling reaction
and RCM as key steps. The required 3,4-diiodoben-
zene derivatives were prepared by diazotization with
sodium nitrite in HCl/H2O or H2SO4 in moderate to
good yields (40–84%). The SM cross-coupling reac-
tion afforded 3,4-diallylbenzene derivatives in good to
excellent yields (71–95%). RCM followed by one-pot
aromatization using DDQ gave acceptable yields of
the aromatized products (82–86%, two steps). The
second strategy for benzoannulation is based on a
double Claisen rearrangement and RCM followed by
oxyanthraquinone (33),[35] 1,4-bis
[allyloxy]-2,3-dimethylben-
G
zene (34),[36] 6,7-dimethyl-5,8-dihydronaphthalene-1,4-diol
(32),[37] and 2,3-diallyl-1,4-dihydroxyanthraquinone (36)[38]
were prepared according to the reported procedures.
General Procedure for Preparation of 2-Iodoaniline
Derivatives
To a stirred solution of aniline derivative (1 equiv.) in a
methanol-water mixture, potassium iodide (0.75 equivs.), po-
one-pot DDQ oxidation to yield the benzoannulated tassium iodate (0.375 equivs.) were added. The resulting
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Table 3. List of various benzoannulated quinones prepared by the RCM and DDQ oxidation sequence.
Entry
Diene
Conditions[a]
RCM product
Aromatized Products
Yield [%][b]
1
42
A
45
51
49
2
3
4
5
43
44
38
40
41
A
B
46
47
48
49
50
52
53
54
55
55
37
51
54
85
91
A
A
A
6
[a]
A: (i) Catalyst 1, dry dichloromethane, reflux, 24 h; (ii) DDQ, benzene, reflux. B: (i) Catalyst 2, dry dichloromethane,
reflux, 24 h; (ii) DDQ, benzene, reflux.
Yield refers to the overall yield obtained after the RCM and aromatization sequence.
[b]
mixture was stirred for 2–5 min and then dilute HCl (1
3). The combined organic layers were washed with dilute
sodium thiosulfate solution, water and brine. The solvent
was evaporated and the crude product was purified by silica
gel column chromatography. Elution of the column with pe-
troleum ether or 1–2% ethyl acetate/petroleum ether mix-
ture gave the desired diiodo derivatives; yield: 63–84%.
equiv.) was added during a period of 45–60 min. The reac-
tion mixture was stirred at room temperature for 6 h and
then filtered. The solid was washed with water and dilute
sodium thiosulfate solution and dried at room temperature
or in an oven to give the corresponding 2-iodoaniline deriv-
atives; yield: 85–96%.
Method B: To cooled, concentrated H SO4 at 08C (1 mL),
2
NaNO2 was added. Then, the amine in glacial acetic acid
was added at the same temperature during a period of
10 min. The resulting mixture was stirred at low temperature
for 30 min and aqueous KI solution was added within 5–
10 min. The reaction mixture was extracted with dichloro-
methane (30 mL”3) and combined organic layers were
washed with dilute sodium thiosulfate solution, water and
brine. The solvent was evaporated to give the crude product
which was purified by column chromatography. Elution of
the column with petroleum ether or 1% ethyl acetate/petro-
leum ether mixture gave the desired diiodo derivatives.
General Procedure for Preparation of 3,4-
Diiodobenzene Derivatives from 2-Iodoaniline
Derivatives
Method A: To a cooled solution of 2-iodoaniline derivative
at 08C in HCl-water (1:1), an aqueous solution of sodium ni-
trite was added within 10 min. The resulting solution was
stirred at 0–58C for 30 min. To the above mixture, an aque-
ous solution of KI was added during a period of 10–15 min.
The reaction mixture was stirred at room temperature for
20–24 h and then extracted with dichloromethane (40 mL”
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General Procedure for Preparation of o-Diallylben-
zene Derivatives via Suzuki–Miyaura Cross-Coupling
Reaction
5,8-Dihydro-2-nitronaphthalene (8)
3,4-Diallylnitrobenzene (7; 44.0 mg, 0.22 mmol), Grubbsꢀ
catalyst 1 (4.4 mg, 3 mol%) in dry dichloromethane (5 mL)
was treated as described in the general procedure for RCM
reaction. At the conclusion of the reaction (20 min, TLC
monitoring), the solvent was evaporated and the resulting
crude product was purified by silica gel column chromatog-
raphy. Elution of the column with 1% ethyl acetate/petrole-
um ether mixture gave the desired product 8 as a pale
yellow liquid; yield: 35 mg (92%); 1H NMR (CDCl3,
400 MHz):[22] d=3.49 (d, J=1.6 Hz, 4H), 5.92–5.94 (m, 2H),
7.23–7.26 (m, 1H), 7.96–7.98 (m, 2H); 13C NMR (CDCl3,
100.6 MHz): d=29.9, 30.1, 121.1, 123.5, 124.0 124.3, 129.35,
135.9, 142.2, 146.4.
In a three-necked, round-bottom flask, the diiodo com-
pound was charged and THF was added followed by CsF
and Pd(PPh3)4. The resulting suspension was stirred at room
G
temperature for 30 min and allylboronate 3 in THF was
added. The reaction mixture was refluxed (70–758C oil-bath
temperature). After completion of the reaction (TLC moni-
toring), the reaction mixture was quenched with water and
extracted with dichloromethane (30 mL”3). The combined
organic layers were washed with water and brine. The sol-
vent was evaporated to give the crude product which was
purified by silica gel column chromatography. Elution of the
column with petroletum ether or 1–2% ethyl aetate/petrole-
um ether mixture gave the desired diallyl derivative; yield:
71–95%.
2-Nitronaphthalene (9)
To a stirred solution of dihydronaphthalene derivative 8
(32 mg, 0.18 mmol) in benzene (8 mL), DDQ (118 mg,
0.46 mmol) was added and the resulting mixture was re-
fluxed for 48 h. Then, the solvent was evaporated under re-
duced pressure and the crude product was purified by silica
gel column chromatography. Elution of the column with 2%
ethyl acetate/petroleum ether mixture gave the desired
product 9 as a yellow solid; yield: 18 mg (60%); mp 75–
788C (Lit. mp 77.8–78.68C).[23] 1H NMR (CDCl3, 300 MHz):
d=7.61–7.93 (m, 2H), 7.93–7.97 (m, 2H), 8.03 (d, J=7.8 Hz,
1H), 8.24 (dd, J=9.0 Hz, 2.1 Hz, 1H), 8.80 (d, J=
2.1 Hz,1H).
General Procedure for RCM and One-Pot Oxidation
by DDQ
To a stirred solution of diallyl derivatives in dry DCM, the
Grubbsꢀ catalyst 1 was added. After completion of the reac-
tion (20–25 min, TLC monitoring), benzene and DDQ were
added to the reaction mixture and refluxed for 48 h. Then,
the solvent was evaporated under reduced pressure and the
crude product was purified by silica gel column chromatog-
raphy. Elution of the column with 1–2% ethyl acetate/petro-
leum ether mixture gave the desired aromatized product;
yield: 82–86%.
Methyl 3-Iodo-4-aminobenzoate (10)
Methyl 4-aminobenzoate[24] (500 mg, 3.31 mmol), KI
(370 mg, 2.23 mmol), KIO3 (236 mg, 1.10 mmol), HCl
(0.5 mL diluted to 5 mL) in methanol/water (3 mL/15 mL)
were treated as described in the general procedure for iodi-
nation. The desired product 10 was obtained as a white
solid; yield: 770 mg (84%); mp 84–888C (Lit. mp 89–
908C).[25]
3,4-Diiodonitrobenzene (6)
2-Iodoaniline (5; 1.0 g, 3.78 mmol), NaNO2 (340 mg,
4.92 mmol), and KI (900 mg, 5.42 mmol) were treated as de-
scribed in method A for diazotization. Elution of the
column with petroleum ether gave the desired product 6 as
a yellow solid; yield: 1.2 g (84%); mp 109–1128C (Lit. mp
108–1108C).[21] 1H NMR (CDCl3, 400 MHz): d=7.87 (dd,
J=8.4 Hz, 2.4 Hz, 1H), 8.06 (d, J=8.4 Hz , 1H), 8.64 (d, J=
2.4 Hz, 1H).
Methyl 3,4-Diiodobenzoate (14)
2-Iodoaniilne (10; 700 mg, 2.53 mmol), NaNO2 (277 mg in
2 mL water, 4.92 mmol), KI (609 mg, 3.63 mmol) were treat-
ed as described in method A for diazotization. Elution of
the column with 1% ethyl acetate/petroleum ether mixture
gave the desired product 14 as a pale yellow solid; yield:
3,4-Diallylnitrobenzene (7)
3,4-Diiodonitrobenzene (6; 100 mg, 0.26 mmol), CsF
(162 mg, 1.06 mmol), Pd(PPh3)4 (37 mg, 12 mol%) and allyl-
G
boronate 3 (180 mg, 1.07 mmol) were treated as described in
a general procedure for diallylation. After completion of the
reaction (8 h, TLC monitoring), work-up according to the
general procedure gave the crude product. Elution of the
column with 1% ethyl acetate/petroleum ether mixture gave
the desired product 7 as a yellow liquid; yield: 49 mg
˜
635 mg (67%); mp 74–768C; IR (neat): n=3060, 2941, 2840,
1720, 1280, 1110, 890, 838, 755 cmÀ1 1H NMR (CDCl3,
;
400 MHz): d=3.83 (s, 3H), 7.56 (dd, J=8.4 Hz, 1.6 Hz, 1H),
7.90 (d, J=8.4 Hz, 1H), 8.39 (d, J=1.6 Hz, 1H); 13C NMR
(CDCl3, 100.6 MHz): d=52.7, 108.1, 114.6, 129.8, 131.1,
139.6, 140.2, 156.4; HR-MS (Q-ToF): m/z=388.8546, calcd.
for C8H7I2O2 (M+H): 388.8536.
˜
(90%); IR (neat): n=3080, 1520, 1344, 992, 915, 840,
812 cmÀ1 1H NMR (CDCl3, 400 MHz): d=3.47 (d, J=
;
5.2 Hz, 4H), 5.19–4.99 (m, 4H), 6.00–5.90 (m, 2H), 7.32 (d,
J=8.4 Hz, 1H), 8.01–8.05 (m, 2H); 13C NMR (CDCl3,
100.6 MHz): d=36.9, 37.1, 117.3, 117.4, 121.7, 124.5, 130.5,
135.3, 135.37, 139.93, 145.9, 146.9; HR-MS (Q-ToF): m/z=
226.0852, calcd. for C12H13NO2Na (M+Na): 226.0844.
Methyl 3,4-Diallylbenzoate (18)
Methyl 3,4-diiodobenzoate (14; 150 mg, 0.39 mmol), CsF
(235 mg , 1.54 mmol), Pd(PPh3)4 (53.5 mg, 12 mol%) and al-
A
lylboronate 3 (260 mg, 1.54 mmol) were treated as described
in the general procedure for diallylation. After completion
of the reaction (48 h, TLC monitoring), reaction mixture
was quenched with water, extracted with dichloromethane
1166
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Adv. Synth. Catal. 2007, 349, 1159 – 1172

Formation of Arenes via Diallylarenes
FULL PAPERS
(30 mL”3). Combined organic layers were washed with
water and brine. Evaporation of the solvent gave the crude
product which was purified by silica gel column chromatog-
raphy. Elution of the column with 1% ethyl acetate/petrole-
um ether mixture gave the desired product 18 as a thick
silica gel column chromatography. Elution of the column
with 0.4% ethyl acetate/petroleum ether mixture gave the
desired product 19 as a yellow liquid; yield: 81 mg (92%).
˜
IR (neat): n=3076, 1724, 1634, 1370, 996, 910, 845,
755 cmÀ1 1H NMR (CDCl3, 400 MHz): d=1.39 (t, J=
;
˜
yellow liquid; yield: 80 mg (95%). IR (neat): n=3080, 1720,
7.2 Hz, 3H), 3.43 (d, J=6.4 Hz, 4H), 4.36 (q, J=7.2 Hz,
2H), 5.11–4.96 (m, 4H), 6.01–5.89 (m 2H), 7.23 (d, J=
8.0 Hz, 1H), 7.86–7.83 (m, 2H); 13C NMR (CDCl3,
100.6 MHz): d=14.5, 37.1, 37.2, 61.0, 116.4, 116.6, 127.9,
128.9, 129.8, 130.9, 136.3, 136.6, 138.3, 143.6, 166.9; HR-MS
(Q-ToF): m/z=231.1385, calcd. for C15H17O2 (M+H):
231.1385.
1
1634, 1110, 992, 919, 845, 796, 760 cmÀ1; H NMR (CDCl3,
300 MHz): d=3.43 (d, J=5.7 Hz, 4H), 3.90 (s, 3H), 5.12–
4.95 (m, 4H), 6.03–5.87 (m, 2H), 7.24 (d, J=8.4 Hz, 1H),
7.83–7.85 (m, 2H); 13C NMR (CDCl3, 100.6 MHz): d=37.0,
37.2, 52.1, 115.6, 116.5, 127.9, 128.5, 129.8, 130.9, 136.2,
136.4, 138.4, 143.6, 167.3; HR-MS (Q-ToF): m/z=217.1230,
calcd. for C14H18NO2 (M+H): 217.1229.
Ethyl 2-Naphtholate (23)
Methyl 2-Naphthoate (22)
To
a stirred solution of ethyl 3,4-diallylbenzoate (19;
To a stirred solution of methyl 3,4-diallylbenzoate (18;
80.0 mg, 0.37 mmol) in dry dichloromethane (5 mL),
Grubbsꢀ catalyst 1 (9.0 mg, 3 mol%) was added. At the con-
clusion of the reaction (25 min, TLC monitoring), DDQ
(255.0 mg, 0.92 mmol) and benzene (10 mL) were added.
The resulting mixture was heated to reflux for 48 h and the
solvent was evaporated under reduced pressure. The crude
product was purified by silica gel column chromatography.
Elution of the column with 1% ethyl acetate/petroleum
ether mixture gave the desired product 22 as a white solid;
yield: 59.0 mg (82%); mp 76–788C (Lit. mp 75–768C).[26]
1H NMR (CDCl3, 400 MHz): d=3.98 (s, 3H), 7.60–7.52 (m,
2H), 7.88 (d, J=8.8 Hz, 2H), 7.95 (d, J=8.0 Hz, 1H), 8.06
(dd, J=8.8 Hz, 1.6 Hz, 1H), 8.61 (s, 1H).
68.0 mg, 0.29 mmol) in dry dichloromtehane (5 mL),
Grubbsꢀ catalyst 1 (7.3 mg, 3 mol%) was added. At the con-
clusion of the reaction (25 min, TLC monitoring), DDQ
(244.0 mg, 0.88 mmol) and benzene (10 mL) were added.
The resulting mixture was heated to reflux for 48 h and sol-
vent was evaporated under reduced pressure and the crude
product was purified by silica gel column chromatography.
Elution of the column with 1% ethyl acetate/petroleum
ether mixture gave the desired product 23 as a pale yellow
liquid; yield: 59.0 mg (82%). 1H NMR (CDCl3,
300 MHz):[29] d=1.45 (t, J=7.2 Hz, 3H), 4.45 (q, J=7.2 Hz,
2H), 7.61–7.51 (m, 2H), 7.88 (d, J=9.0 Hz, 2H), 7.95 (d, J=
8.7 Hz, 1H), 8.07 (dd, J=8.7 Hz, 1.5 Hz, 1H), 8.61 (s, 1H).
Ethyl 3-Iodo-4-aminobenzoate (11)
2-Iodo-4-nitro-1-naphthylamine (12)
Ethyl 4-aminobenzoate[27] (2.0 g, 12.1 mmol), KI (1.34 g,
8.07 mmol), KIO3 (870 mg, 4.04 mmol), HCl (1.3 mL diluted
to 10 mL) in methanol/water (10 mL/60 mL) were treated as
described in the general procedure for iodination to provide
the desired product 11 as a white solid; yield: 3.4 g (95%);
mp 82–868C (Lit. mp 838C).[28]
4-Nitro-1-naphthylamine[30] (2.0 g, 10.6 mmol), KI (1.17 g,
7.1 mmol), KIO3 (0.76 g, 3.05 mmol), HCl (1.2 mL diluted to
10 mL) in methanol/water (10 mL/60 mL) were treated as
described in the general procedure to give the title com-
pound 12 as a yellow solid; yield: 3.1 g (93%); mp 232–
2348C (Lit. mp 2328C).[31] 1H NMR (CDCl3, 400 MHz): d=
5.46 (bs, 2H), 7.60–7.56 (m, 1H), 7.76–7.71 (m, 1H), 7.84 (d,
J=8.8 Hz, 1H), 8.76 (s, 1H), 8.90 (d, J=8.8 Hz, 1H).
Ethyl 3,4-Diiodobenzoate (15)
2-Iodoaniline (11; 1.5 g, 5.15 mmol), NaNO2 (462 mg,
6.70 mmol), KI (1.2 g, 7.22 mmol) were treated as described
in method A for diazotization. Elution of the column with
1% ethyl acetate/petroleum ether mixture gave the desired
product 15 as a white solid; yield: 1.3 g (68%); mp 74–768C.
3,4-Diallyl 1-Nitronaphthalene (20)
3,4-Diiodo-1-nitronaphthalene[11] (16; 150 mg, 0.35 mmol),
CsF (215 mg, 1.42 mmol), Pd(PPh3)4 (45.0 mg, 12 mol%)
A
and allylboronate 3 (240 mg, 1.42 mmol) were treated as de-
scribed in the general procedure for diallylation. After com-
pletion of reaction (48 h, TLC monitoring), general work-up
as described in a general procedure gave the crude product
which was purified by silica gel column chromatography.
Elution of the column with petroleum ether gave the de-
sired product 20 as a yellow liquid; yield: 63 mg (71%); IR
˜
˜
IR (neat): n=3076, 2933, 2896, 1715, 1275, 1110, 755, 890,
838 cmÀ1 1H NMR (CDCl3, 400 MHz): d=1.39 (t, J=
;
7.2 Hz, 3H), 4.37 (q, J=7.2 Hz, 2H), 7.66 (dd, J=8.0 Hz,
2.0 Hz, 1H), 7.95 (d, J=8.4 Hz, 1H), 8.47 (d, J=1.6 Hz,
1H); 13C NMR (CDCl3, 75.4 MHz): d=14.3, 61.6, 107.9,
114.3, 129.8, 131.5, 139.5, 140.1, 164.8; HR-MS (Q-ToF):
m/z=402.8691, calcd. for C9H9O2I2 (M+H): 402.8692.
(neat): n=3092, 1520, 1344, 990, 923, 825, 740 cmÀ1
;
1H NMR (CDCl3, 400 MHz) d=3.62–3.60 (m, 2H), 3.91–
3.89 (m, 2H), 4.89–4.83 (m, 1H), 5.20–5.01 (m, 3H), 6.09–
5.96 (m, 2H), 7.68–7.59 (m, 2H), 8.08 (s, 1H), 8.11 (d, J=
8.0 Hz 1H), 8.53 (dd, J=8.0 Hz, 1.6 Hz, 1H); 13C NMR
(CDCl3, 100.6 MHz) d=32.8, 37.6, 116.9, 117.3, 123.5, 124.4,
125.1, 126.1, 127.5, 128.3, 133.6, 134.9, 135.1, 135.7, 140.7,
145.7; HR-MS (Q-ToF): m/z=254.1184, calcd. for
C16H16NO2 (M+H) : 254.1181.
Ethyl 3,4-Diallylbenzoate (19)
Ethyl 3,4-diiodobenzoate (15; 150 mg, 0.37 mmol), CsF
(227 mg , 1.49 mmol), Pd(PPh3)4 (51.0 mg, 12 mol%) and al-
A
lylboronate 3 (250 mg, 1.49 mmol) were treated as described
in the general procedure for diallylation. At the conclusion
of reaction (48 h, TLC monitoring), general work-up with
dichloromethane gave crude product which was purified by
Adv. Synth. Catal. 2007, 349, 1159 – 1172
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1167

Sambasivarao Kotha et al.
FULL PAPERS
2H), 5.10 (dd, J=8.8 Hz, 1.6 Hz, 2H), 5.99–5.89 (m 2H),
7.27 (d, J=8.8 Hz, 1H,), 7.77–7.75 (m, 2H); 13C NMR
(CDCl3, 100.6 MHz): d=26.6, 37.0, 37.1, 116.4, 116.7, 128.7,
129.6, 129.9, 135.6, 136.0, 136.3, 138.5, 143.9, 198.1; HR-MS
(Q-ToF): m/z=201.1286, calcd. for C14H17O (M+H):
201.1279.
9-Nitrophenanthrene (24)
To a stirred solution of 3,4-diallyl-1-nitronaphthalene (20;
53.0 mg, 0.21 mmol) in dry dichloromethane (5 mL),
Grubbsꢀ catalyst 1 (5.2 mg, 3 mol%) was added. At the con-
clusion of the reaction (30 min, TLC monitoring), DDQ
(244.0 mg, 0.88 mmol) and benzene (10 mL) were added.
The resulting mixture was heated to reflux for 48 h and the
solvent was removed under reduced pressure and the crude
product was purified by silica gel column chromatography.
Elution of the column with 1% ethyl acetate/petroleum
ether mixture gave the desired product 25 as a pale yellow
solid; yield: 38.0 mg (82%); mp 114–1178C (Lit. mp 115–
1178C).[31] 1H NMR (CDCl3, 400 MHz): d=7.86–7.69 (m,
4H), 8.02 (d, J=7.6 Hz, 1H), 8.48 (s, 1H), 8.50 (dd, J=
7.6 Hz, 2.0 Hz, 1H), 8.71 (d, J=8.4 Hz, 1H), 8.77 (dd, J=
6.8 Hz, 2.0 Hz, 1H).
2-Acetylnaphthalene (25)
To a stirred solution of 3,4-diallylacetophenone (21; 25.0 mg,
0.11 mmol) in dry dichloromethane (5 mL), Grubbsꢀ catalyst
1 (2.7 mg, 3 mol%) was added. At the conclusion of the re-
action (25 min, TLC monitoring), DDQ (255.0 mg,
0.92 mmol) and benzene (10 mL) were added. The resulting
reaction mixture was heated to reflux for 48 h and solvent
was removed under reduced pressure. The crude product
was purified by silica gel column chromatography. Elution
of the column with 2% ethyl acetate/petroleum ether mix-
ture gave the desired product 25 as a white solid; yield:
18.0 mg (82%); mp 76–788C (Lit. mp 76–778C).[34] 1H NMR
(CDCl3, 400 MHz): d=2.73 (s, 3H), 7.62–7.54 (m, 2H), 7.89
(t, J=8.4 Hz, 6.4 Hz, 2H), 7.97 (d, J=7.6 Hz, 1H), 8.04 (dd,
J=8.8 Hz, 1.6 Hz, 1H), 8.47 (s, 1H).
3-Iodo-4-aminoacetophenone (13)
4-Aminoacetophenone (2.0 g, 12.1 mmol), KI (1.34 g,
8.07 mmol), KIO3 (870 mg, 4.04 mmol), HCl (1.3 mL diluted
to 10 mL) in methanol/water (10 mL/60 mL) were treated
according to the general procedure for iodination to provide
the desired product 13 as a yellow solid; yield: 2.56 g
(70%); mp 53–558C (Lit. mp 50–528C).[33] 1H NMR (CDCl3,
400 MHz): d=8.28 (d, J=2.0 Hz, 1H), 7.76 (dd, J=8.4 Hz,
2.0 Hz, 1H), 6.71 (d, J=8.8 Hz, 1H), 4.61 (bs, 2H), 2.50 (s,
3H).
5,8-Bis
(35)
A
To a solution of diol 32[37] (1.1 g, 5.7 mmol) in dry acetone,
potassium carbonate (3.2 g, 22.8 mmol) and allyl bromide
(2.1 gm, 17.1 mmol) were added. The reaction mixture was
stirred at room temperature for 24 h and then filtered
through a celite pad. The residue was washed with dichloro-
methane (3”30 mL). Evaporation of the solvent gave the
crude product, which was charged on a silica gel column.
Elution of the column with 1% ethyl acetate/petroleum
ether mixture gave the compound 35 as a white crystalline
solid; yield: 1.24 g (81%); mp 978C. 1H NMR (CDCl3,
300 MHz): d=1.77 (s, 6H), 3.24 (s, 4H), 4.49 (dt, J=5.1,
1.7 Hz, 4H), 5.26 (dd, J=10.5, 1.5 Hz, 2H); 5.41 (dd, J=
17.3, 1.5 Hz, 2H); 6.0–6.13 (m, 2H), 6.59 (s, 2H); 13C NMR
(CDCl3, 75.4 MHz): d=18.6, 31.1, 69.1, 108.1, 116.8, 122.4,
125.5, 133.9, 149.7; anal. calcd. (%) for C18H22O2: C 79.96, H
8.20; found: C 79.90, H 7.74.
3,4-Diiodoacetophenone (17)
2-Iodo aniline (13; 800 mg, 3.05 mmol) in AcOH (6 mL),
NaNO2 (275 mg, 3.98 mmol), KI (738 mg, 4.45 mmol) and
concentrated H2SO4 (1 mL) were treated as described in
method B for diazotization. Elution of the column with 1%
ethyl acetate/petroleum ether mixture gave the desired
product 17 as a yellow crystalline solid; yield: 550 mg
˜
(48%); mp 73–768C. IR (neat): n=3060, 2917, 2847, 1683,
1
1564, 1090, 900, 808 cmÀ1; H NMR (CDCl3, 400 MHz): d=
2.56 (s, 3H), 7.57 (dd, J=8.4 Hz, 2.0 Hz, 1H), 7.98 (d, J=
8.4 Hz, 1H), 8.38 (d, J=2.0 Hz, 1H); 13C NMR (CDCl3,
75.4 MHz): d=26.7, 108.7, 114.9, 128.5, 137.8, 139.0, 139.8,
196.2. HR-MS (Q-ToF): m/z=372.8596, calcd. for C8H7OI2
(M+H): 372.8586.
Claisen Rearrangement of Compound 34 under
Conventional Heating Conditions
3,4-Diallylacetophenone (21)
A solution of 34 (464 mg, 2.12 mmol) in xylene (8 mL) was
refluxed for 12 h. Xylene was distilled off under reduced
pressure and the crude reaction mixture was directly charg-
ed on a silica gel column. Elution of the column with petro-
3,4-Diiodoacetophenone (17; 150 mg, 0.40 mmol), CsF
(245 mg, 1.61 mmol), Pd(PPh3)4 (56.0 mg, 12 mol%) and al-
G
lylboronate 3 (250 mg, 1.49 mmol) were treated as described
in the general procedure for diallylation. At the conclusion
of the reaction (TLC monitoring, 48 h), work-up procedure
as described in a general procedure gave the crude product
which was purified by silica gel column chromatography.
Elution of the column with 2% ethyl acetate/petroleum
ether mixture and careful removal of solvent at lower tem-
perature (<408C) under reduced pressure gave the desired
product 21 as a colorless liquid which turned yellowish
green on standing; yield: 70 mg (89%) Note: The product is
leum ether gave 2,3-diallyl-5,6-dimethyl[1,4]benzoquinone
A
(38) as a yellow liquid; yield: 121 mg (26%); Rf =0.5 (silica
À1
˜
gel, EtOAc/petroleum ether, 1:49). IR (neat): n=1651 cm
(C=O);
UV
(CHCl3):
lmax
(e)=276 nm
(3542 molÀ1 dm3 cmÀ1); H NMR (CDCl3, 400 MHz): d=2.03
(s, 6H), 3.27 (dt, J=6.4, 1.6 Hz, 4H), 5.02–5.09 (m, 4H),
5.75–5.85 (m, 2H); 13C NMR (CDCl3, 100.6 MHz): d=12.5,
30.6, 116.8, 134.2, 140.8, 142.3, 187.2; HR-MS (Q-ToF):
m/z=217.1228, calcd. for C14H17O2 (M+H): 217.1229.
1
˜
volatile. IR (neat): n=3080, 1680, 1634, 1356, 996, 910, 830,
1
755 cmÀ1; H NMR (CDCl3, 400 MHz): d=2.59 (s, 3H), 3.44
(dd, J=6.4 Hz, 1.6 Hz, 4H), 5.00 (dd, J=8.8 Hz, 1.6 Hz,
1168
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Formation of Arenes via Diallylarenes
FULL PAPERS
then allowed to stir at room temperataure for 24 h. and then
filtered through a celite pad. The residue was washed with
dichloromethane (3”10 mL). Evaporation of the solvent
gave the crude product, which was charged on a silica gel
column. Elution of the column with 3% ethyl acetate in pe-
troleum ether gave the compound 42 as a yellow liquid;
Claisen Rearrangement of Compound 35 under
Conventional Heating Conditions
A solution of 35 (100 mg, 0.37 mmol) in N,N-dimethylaniline
(8 mL) was refluxed for 12 h. The solvent was distilled off
under reduced pressure and the crude reaction mixture was
charged on a silica gel column. Elution of the column with
1% ethyl acetate/petroleum ether gave 2,3-diallyl-6,7-dime-
thylnaphthalene-1,4-(5H,8H)-dione (40) as a yellow liquid;
yield: 49 mg (49%); Rf =0.26 (silica gel, EtOAc/petroleum
1
yield: 109 mg (98%). H NMR (CDCl3, 300 MHz): d=3.59
(dt, J=3.9, 1.8 Hz, 4H), 3.91 (s, 6H; 2 ” OCH3), 4.94 (d,
J=17.2 Hz, 2H), 5.08 (d, J=10.2 Hz, 2H), 5.92–6.05 (m,
2H), 7.71–7.76 (m, 2H), 8.19 (dd, 2H, J=5.7, 3.3 Hz).
ether, 1:49). IR (neat): n=1656; 1H NMR (CDCl3,
˜
400 MHz): d=1.73 (s, 6H), 3.0 (s, 4H), 3.27 (d, J=6.0 Hz,
4H), 5.03–5.09 (m, 4H), 5.75–5.85 (m, 2H); 13C NMR
(CDCl3, 100.6 MHz): d=18.2, 30.2, 30.6, 116.7, 121.9, 134.0,
139.3, 142.0, 186.6; MS (Q-ToF): m/z 269.0 [C18H17O2 (M+
H)].
2,3-Diallyl-1,4-diethoxyanthraquinone (43)
To a solution of 36 (68 mg, 0.21 mmol) in dry acetone, ethyl
bromide (0.2 mL, 2.9 mmol) sodium iodide (319 mg,
2.1 mmol) and sodium hydroxide (85 mg, 2.1 mmol) were
added. The reaction mixture was then allowed to reflux for
24 h. It was then filtered through a celite pad. The residue
was washed with dichloromethane (3”10 mL). Evaporation
of the solvent gave the crude product, which was charged on
a silica gel column. Elution of the column with 3% ethyl
acetate in petroleum ether gave compound 43 as a yellow
crystalline solid; yield: 50 mg (63%); mp 708C. IR (neat):
General Procedure for Claisen Rearrangement under
MWI using Silica Gel Support
To a dichloromethane solution of starting material in a
beaker, was added pre-activated (pre-activation of the silica
gel was achieved by MWI [Ken Star, OM-992E] for 5 min)
silica gel (100–200 mesh, 4–10 times the weight of the start-
ing substrate) and then the solvent was evaporated. The re-
sulting homogeneous mixture of the substrate and silica gel
was then irradiated in a microwave oven (power 800 watt)
for optimized time. The crude reaction mixture was purified
by flash chromatography. Elution of the column with an ap-
propriate mixture of ethyl acetate and petroleum ether gave
the desired product.
À1
1
˜
n=1673 cm (C=O); H NMR (CDCl3, 300 MHz): d=1.52
(t, J=7 Hz, 6H), 3.59 (dt, J=5.6, 2 Hz, 4H), 4.01(q,
J=6.8 Hz, 4H), 4.92 (d, J=17.2 Hz, 2H), 5.06 (d, J=
10.2 Hz, 2H) 5.93–6.03 (m, 2H), 7.69–7.74 (m, 2H), 8.18
(dd, J=5.6, 3.2 Hz, 2H); HR-MS (Q-ToF): m/z=377.1769,
calcd. for C24H25O4 (M+H): 377.1753.
2,3-Diallyl-9,10-dioxo-9,10-dihydroanthracene-1,4-diyl
Diacetate (44)[40]
2,3-Diallyl-5,6-dimethyl[1,4]benzoquinone (38)
G
To a solution of 36 (64 mg, 0.2 mmol) in dry pyridine
(2 mL), acetic anhydride (0.1 mL, 1 mmol) was added. The
reaction mixture was then allowed to stir at room tempera-
ture for 24 h. Water (30 mL) and diethyl ether (30 mL) were
added and the solution was washed with 1 N HCl and satu-
rated aqueous NaHCO3 (10 mL), then dried over anhydrous
MgSO4. Evaporation of the solvent gave the crude product,
which was charged on a silica gel column. Elution of the
column with 6% ethyl acetate in petroleum ether gave the
compound 44 as a yellow crystalline solid; yield: 77 mg
Compound 34 (517 mg, 2.37 mmol) was mixed with silica gel
(2.4 g) and then irradiated in a microwave oven for 7 min by
following a general procedure. The crude reaction mixture
was then directly charged on a silica gel column. Elution of
the column with petroleum ether gave the compound 38 as
a yellow liquid; yield: 200 mg (39%). The H NMR spectral
data of this compound were found to be identical to those
of the earlier reported compound.
1
1
(95%); mp 1518C. H NMR (CDCl3, 300 MHz): d=2.49 (s,
2,3-Diallyl-6,7-dimethyl[1,4]naphthoquinone (41)
R
6H), 3.49 (m, 4H), 5.02 (d, J=17.2 Hz, 2H), 5.09 (d, J=
10.2 Hz, 2H), 5.79–5.89 (m, 2H), 7.7–7.74 (m, 2H), 8.14 (dd,
J=5.8, 3.4 Hz, 2H).
Compound 35 (113 mg, 0.42 mmol) was mixed with silica gel
(3.9 g) and then irradiated in a microwave oven for 15 min
by following a general procedure. The crude reaction mix-
ture was charged on a silica gel column. Elution of the
column with 1% Ethyl acetate/petroleum ether gave com-
pound 41 as a yellow liquid; yield: 48 mg (43%). IR (neat):
6,11-Dimethoxytetracene-5,12-dione (51)
To a solution of compound 42 (49 mg, 0.14 mmol) in dry de-
gassed DCM (12 mL) was added the Grubbsꢀ catalyst 1
(6 mg, 5 mol%). The reaction mixture was refluxed for 24 h.
In the same pot DDQ (48 mg, 0.21 mmol) dissolved in dry
benzene (15 mL) was added and refluxed for an additional
24 h. Then, the reaction mixture was concentrated and the
crude product was purified by a silica gel column. Elution of
the column with 3% ethyl acetate/petroleum ether gave
compound 51 as a yellow crystalline solid; yield: 22 mg
(47%); Rf =0.55 (silica gel, EtOAc/petroleum ether 1:9);
mp 1888C (Lit. mp 183–1848C).[41] 1H NMR (CDCl3,
300 MHz): d=4.14 (s, 6H), 7.74–7.78 (m, 4H; ArH), 8.27
(dd, J=5.9, 3.5 Hz, 2H), 8.42 (dd, J=6.3, 3.3 Hz, 2H);
À1
1
˜
n=1661 cm (C=O); H NMR (CDCl3, 400 MHz): d=2.38
(s, 6H); 3.41 (dt, J=6.4, 1.6 Hz, 4H); 5.05–5.14 (m, 4H);
5.82–5.92 (m, 2H); 7.81 (s, 2H); 13C NMR (CDCl3,
100.6 MHz): d=20.3, 30.9, 116.9, 127.5, 130.2 121.9, 134.2,
143.4, 144.9, 185.0; HR-MS (Q-Tof): m/z=267.1382, calcd.
for C18H19O2 (M+H): 267.1385.
2,3-Diallyl-1,4-dimethoxyanthraquinone (42)[39]
To a solution of 36 (102 mg, 0.32 mmol) in dry acetone, po-
tassium carbonate (221 mg, 1.6 mmol) and methyl iodide
(0.2 mL, 3.2 mmol) were added. The reaction mixture was
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FULL PAPERS
13C NMR (CDCl3, 75.4 MHz): d=63.3, 120.8, 124.8, 126.8,
130, 132.8, 133.6, 134.9, 155.8 (C-6, C-11), 182.7 (C-5, C-12).
0.21 mmol) dissolved in dry benzene (15 mL) was added and
refluxed for 24 h. Then, the reaction mixture was concen-
trated and the crude product was purified by a silica gel
column. Elution of the column with 1% ethyl acetate/petro-
6,11-Diethoxytetracene-5,12-dione (52)
leum ether gave 2,3-dimethyl-anthraquinone (55) as
a
To a solution of compound 43 (42 mg, 0.11 mmol) in dry de-
gassed DCM (12 mL) was added the Grubbsꢀ catalyst 1
(5 mg, 5 mol%). The reaction mixture was refluxed for 24 h.
In the same pot DDQ (39 mg, 0.17 mmol) dissolved in dry
benzene (15 mL) was added and refluxed for 24 h. Then, the
reaction mixture was concentrated and the crude product
was purified by a silica gel column. Elution of the column
with 4% ethyl acetate/petroleum ether gave the compound
52 as a yellow crystalline solid; yield: 14 mg (37%); Rf =0.6
yellow crystalline solid; yield: 21 mg (91%); Rf =0.15 (silica
gel, EtOAc/petroleum ether, 1:49); mp 212–2138C (Lit. mp
210–2128C).[44]
One-Pot RCM and Aromatization of 41
To a solution of compound 41 (26 mg, 0.097 mmol) in dry
degassed DCM (5 mL) was added the Grubbsꢀ catalyst 1
(4 mg, 5 mol%). The reaction mixture was stirred for 6 h at
room temperature. In the same pot DDQ (33 mg,
0.14 mmol) dissolved in dry benzene (15 mL) was added and
refluxed for 24 h. Then, the reaction mixture was concen-
trated and the crude product was purified by a silica gel
column. Elution of the column with 1% ethyl acetate/petro-
(silica gel, EtOAc/petroleum ether, 1:9); mp 152–1538C. IR
À1
˜
(neat): n=1675 cm (C=O); UV (CHCl3): lmax (e)=297 nm
(10159 molÀ1 dm3 cmÀ1); 1H NMR (CDCl3, 300 MHz): d=
1.66 (t, J=6.9 Hz, 6H), 4.26 (q, J=7 Hz, 4H), 7.71–7.78 (m,
4H), 8.27 (dd, J=5.7, 3.3 Hz, 2H), 8.43 (dd, J=6.6, 3.3 Hz,
2H); 13C NMR (CDCl3, 75.4 MHz): d=15.8, 72.0, 121, 125,
126.8, 129.9, 133.2, 133.5, 135.1, 154.9, 183.0; HR-MS (Q-
ToF): m/z=347.1290, calcd. for C22H19O4 (M+H): 347.1283.
leum ether gave 2,3-dimethyl-anthraquinone (55) as
a
yellow crystalline solid; yield: 21 mg (91%). The melting
point of this compound was found to be identical to that of
the earlier reported compound.
6,11-Diacetoxytetracene-5,12-dione (53)[42]
To a solution of compound 44 (37 mg, 0.09 mmol) in dry de-
gassed DCM (12 mL) was added the Grubbsꢀ catalyst 2
(4 mg, 5 mol%). The reaction mixture was refluxed for 24 h.
In the same pot DDQ (31 mg, 0.14 mmol) dissolved in dry
benzene (15 mL) was added and refluxed for 24 h. Then, the
reaction mixture was concentrated and the crude product
was purified by a silica gel column. Elution of the column
with 10% ethyl acetate/petroleum ether gave the compound
53 as a yellow crystalline solid; yield: 17 mg (51%); Rf =
0.22 (silica gel, EtOAc/petroleum ether, 3:47). 1H NMR
(CDCl3, 300 MHz): d=2.66 (s, 6H), 7.74–7.8 (m, 4H), 8.19
(dd, J=7.7, 3 Hz, 2H), 8.24 (dd, J=6, 3.3 Hz, 2H);
13C NMR (CDCl3, 75.4 MHz): d=21.3, 119.9, 124, 127.1,
130.7, 131.3, 134.4, 135.1, 146.4, 169.3, 181.7.
Acknowledgements
We would like to thank DST and DST (NSTI), New Delhi,
for financial support. V. R. S. and K. M. are thankful to
CSIR, New Delhi for the award of fellowships.
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