Ortho-quinodimethane from anthracene epidioxide: Scope of the Diels-Alder reaction and mild preparation of naphthalene derivatives

Article abstract of DOI:10.1016/j.crci.2014.01.024

The thermal isomerisation of anthracene epidioxide 3 has been known to give phenylenedioxy-ortho-quinodimethane 5 as a reactive transient. We presented herein the scope of the Diels-Alder reaction of this transient 5 with some dienophiles. In addition, a mild synthesis of naphthalene derivatives has been developed via base-induced cleavage of the obtained Diels-Alder adducts.

Full text of DOI:10.1016/j.crci.2014.01.024

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C. R. Chimie 17 (2014) 1075–1079
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Preliminary communication/Communication
ortho-Quinodimethane from anthracene epidioxide: Scope of
the Diels–Alder reaction and mild preparation of naphthalene
derivatives
´
´
`
ortho-Quinodimethane par thermolyse de l’epidioxyde d’anthracene :
´
´
´
´
´
reaction de Diels–Alder et preparation douce de derives naphtaleniques
1
*
*
´
Bernard Siret , Sebastien Albrecht , Albert Defoin
Universite´ de Haute Alsace, Laboratoire de chimie organique et bioorganique, EA4466, Institut Jean-Baptiste-Donnet, 3bis,
rue Alfred-Werner, 68093 Mulhouse cedex, France
A R T I C L E I N F O
A B S T R A C T
Article history:
The thermal isomerisation of anthracene epidioxide
3 has been known to give
Received 12 November 2013
Accepted after revision 28 January 2014
Available online 23 October 2014
phenylenedioxy-ortho-quinodimethane 5 as a reactive transient. We presented herein
the scope of the Diels–Alder reaction of this transient 5 with some dienophiles. In addition,
a mild synthesis of naphthalene derivatives has been developed via base-induced cleavage
of the obtained Diels–Alder adducts.
Keywords:
ß 2014 Acade´mie des sciences. Published by Elsevier Masson SAS. All rights reserved.
ortho-Quinodimethane
Cycloaddition
Elimination
´
´
R E S U M E
´
Mots cles :
L’isome´risation thermique de l’e´pidioxyde de l’anthrace`ne avait e´te´ de´crite pour donner
ortho-Quinodime´thane
´
´
´
`
´
´
l’intermediaire reactif 5 phenylenedioxy-ortho-quinodimethane. Nous presentons les
Cycloaddition
´
´
´
limitations de sa reaction de Diels–Alder avec quelques dienophiles. En complement, nous
de´crivons une synthe`se simple de de´rive´s naphtale´niques par coupure basique des adduits
obtenus.
´
Elimination
´
´
´
´
ß 2014 Academie des sciences. Publie par Elsevier Masson SAS. Tous droits reserves.
1. Introduction
[2,3], and several reviews emphasised the importance of
these transients as tools for the synthesis of cyclic organic
Ortho-quinodimethanes are reactive species that are
not isolable, but have been suspected as transients in
1959 by Cava et al. [1]. They were originally obtained by the
double elimination of
thermal opening of the corresponding benzocyclobutenes
compounds [4–9]. An interesting reaction was the direct
formation of the naphthalene derivatives 2 by Diels–Alder
reaction with dibromo-ortho-xylylene 1 (generated from
tetrabromoxylene) with spontaneous loss of HBr [1,10,11]
(Scheme 1).
a,
a0-dibromo-ortho-xylenes [1] or by
An early study, presented in Scheme 2, showed that the
thermal isomerisation of anthracene endoperoxide 3 led to
ortho-quinodimethane 5 through diepoxide 4 and finally to
*
Corresponding authors.
two successive dimers of 5, an original [8
the normal [8 +2 ] one [12a]. Both isomeric transients 4
and 5 could be trapped with maleic anhydride (6a) or
p+6p] one and
E-mail addresses: sebastien.albrecht@uha.fr (S. Albrecht), albert.de-
p
p
foin@uha.fr (A. Defoin).
1
LAB SA, 25, rue Bossuet, 69455 Lyon cedex 06, France.
1631-0748/$ – see front matter ß 2014 Acade´mie des sciences. Published by Elsevier Masson SAS. All rights reserved.
http://dx.doi.org/10.1016/j.crci.2014.01.024

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1076
B. Siret et al. / C. R. Chimie 17 (2014) 1075–1079
Br
Br
in order to favour the reaction with ortho-quinodimethane
5, i.e. in refluxing chlorobenzene (ca. 132 8C) for 1 h in
the presence of a dienophile in slight excess (ca 1.2 equiv.).
Using 1,4-benzoquinone 10a, 1,4-naphthoquinone 10b
or trans-dibenzoylethylene 11 as dienophiles, adducts 14a,
14b or 15, respectively, were isolated in good yields
(60–70%).
R
R
+
R'
R'
1
2
In the particular case of benzoquinone 10a, a double
addition was observed when epidioxide 3 was used in two-
fold excess. However, the adduct could not be isolated as a
pure compound and was treated directly with a base (see
below).
Scheme 1.
N-methylmaleimide (6b) to give the isolated endo adducts
7b and 8a,b, respectively [12b]. From these latter adducts,
a
base-catalysed or thermal aromatisation into the
corresponding naphthalene compounds 9a and 9b has
been observed, with the release of catechol as a by-product
[12b].
2.2. Case of less reactive dienophiles
Cyclohex-2-en-1-one, cyclohexene, and coumarin were
unreactive and dimers of 5 were only observed. In the case
of the cyclopentenone 12, the adduct 16 was isolated in
poor yield (20–30%) and required to heat under refluxing
benzene for 16 h with an 8-fold excess of the dienophile
(Scheme 3). An inactivated double bond or a double bond
activated by only one carbonyl function was also too less
reactive for this Diels–Alder reaction to compete with
dimerization. The more reactive 5-membered ring 12 gave
only poorly the desired adduct.
This synthesis of naphthalene compounds used only
thermal and base-induced transformations and was also
suitable to synthetize acid-sensitive compounds. The use
of this ortho-quinodimethane 5 in organic synthesis has
never been studied, although the latter was very easy to
obtain from the cheap anthracene. The purpose of this
work was to investigate the scope of this Diels–Alder
reaction and the further formation of naphthalene
derivatives.
2.3. Structure of the adducts
2. Results and discussion
In all cases, we obtained a single adduct. Adduct 15
possessed the benzoyl groups in trans relation, as indicated
2.1. Case of reactive dienophiles
by the important coupling between the protons in
a-
The addition of N-methylmaleimide 6a or maleic
anhydride 6b has already been studied in the initial study
of the thermal isomerisation of anthracene epidioxide 3 in
refluxing benzene. The corresponding adducts 7b (10%)
and 8a,b (70–76%) have been isolated along with minute
amounts of anthraquinone [12b].
position to the carbonyl functions (J = 8 Hz). We assumed
that adducts 14a,b and 16 possessed an endo-configuration
(see Scheme 3) as it has already been demonstrated for 8b
[12b]. This was confirmed in 1H NMR spectra of 14a and
14b by the clear deshielding of the protons H-
a in
a
-position to the carbonyl groups ( 4.40 and 4.05 ppm,
d
In the present work (Scheme 3), the thermal isomerisa-
tion of epidioxide 3 was performed at higher temperature
respectively) in comparison to the corresponding protons
benzene
O
Dimers
O
O
O
O
80°C, 16 h
O
3
5
4
O
O
X
6a,b
O
B (-)
O
O
X
O
O
a X = O
b X = NMe
O
O
O
N
8a,b
7b
9a,b
X
O
O
Scheme 2.

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B. Siret et al. / C. R. Chimie 17 (2014) 1075–1079
1077
O
NEt3
double adduct
O
rt, 63%
2 steps
0.5 equiv.
1 equiv.
60%
O
O
17
O
O
NEt3
O
10a
O
O
rt, 95%
monoadduct
O
O
14a
14b
15
18a
O
O
O
O
NEt3
PhCl
65-70%
O
O
O
3
rt, 95%
132°C, 1 h
(C6H6, 80°C,
16 h for 12)
O
O
5
10b
18b
O
O
O
NEt3
O
O
Ph
Ph
65%
100°C
68%
O
O
11
19
O
O
O
NEt3
O
O
100°C
68%
O
20-30%
12
16
20
Scheme 3.
of the similar adducts 21a [13] and 21b [14] of the
quinones 10a and 10b with cyclohexadiene ( 3.22 and
2.4. Base-induced cleavage of the adducts
d
3.17, respectively), as depicted in Scheme 4. This deshield-
ing was due to the influence of the nearby intracyclic
oxygen atoms of the veratrole moiety. In the case of
the non-symmetrical adduct 15, this important effect
Instead of an aqueous sodium carbonate solution under
refluxing THF as originally described [12b], we have
preferred to use the triethylamine as a more suitable and
efficient base (Scheme 3). For mono-adducts 14a and 14b,
the addition of an excess of triethylamine at room
temperature was sufficient to cleave these adducts into
1,4-anthraquinone 18a or naphthacene-5,12-quinone 18b,
which were isolated in good yields by simple crystal-
lisation and washing in order to discard the formed
catechol. It is worth noting that this transformation could
shifted one of the H-
a protons at 5.90 ppm, with also a
deshielding of 1.4 ppm with respect to the other H-
(at 4.50 ppm).
a
O
O
O
O
be carried out in
a one-pot process. For instance,
endoperoxide 3 was refluxed with a slight excess of
benzoquinone 10a for 1 h. The solvent was then partially
evaporated, and after addition of an excess of triethyla-
mine, quinone 18a was isolated. However, using half the
O
O
O
14a
14b
amount of 10a led to
a double addition of ortho-
H
H
quinodimethane 5 onto this benzoquinone, followed by
a double cleavage after the addition of triethylamine to
give pentacenequinone 17. In both the cases, the overall
yield of quinones 18a or 17 was similar (ca 65%).
Concerning adducts 15 and 16, their cleavage with
triethylamine was more difficult and was achieved under
refluxing 1-propanol for one day to give the known 2,3-
dibenzoylnaphthalene 19 [15] and benzo[f]indanone 20
[11] in 68% yield, respectively. In these cases, the catechol
by-product was discarded by oxidation of the crude
product on silica gel plates (see Experimental part).
δ 4.40
δ 4.05
O
O
O
21b
δ 3.17
21a
δ 3.08
H
H
O
O
Scheme 4.

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B. Siret et al. / C. R. Chimie 17 (2014) 1075–1079
Actually, the dibromo-ortho-quinodimethane transient
adduct isolated by crystallisation and washing in the given
solvent.
1 was more reactive than the ortho-quinodimethane 5
intermediate. This was exemplified with benzoindenone
20 [11], which was obtained in better yield with dibromo
1. However, the formation of reactive hydrobromic acid
limited its use, even if the addition of calcium carbonate
improved the conditions [16].
4.3.2. Benzoquinone adduct 14a: general procedure with 3
(0.3 g, 1.43 mmol) and 10a (0.19 g, 1.76 mmol, 1.23 equiv.)
Cream crystals from acetone, 60% yield, mp
(dec) > 290 8C (C6H5Cl).
IR (KBr): 1670 (C5O), 1485, 1240, 810, 760 cmꢀ1. UV
(THF),
(3.25) nm. 1H NMR (CDCl3):
2 H, H-6, H-11); 6.80 (s, 4 H, H-1 to H-4); 7.20 (s, 6 H, 2 H-
H-7 to H-10). 13C NMR (CDCl3):
52.1 (2 C- ); 81.1 (C-6, C-
11); 123.2, 124.6 (C-1 to C-4); 129.6, 130.4 (C-7 to C-11);
133.5 (C-6a, C-10a); 141.1 (2 C- ); 149.0 (C-4a, C-12a);
l
max(log
e
): 385 (1.78); 283 (3.19); 270 (3.26); 262
3. Conclusion
d
4.40 (m, 2 H, 2 H- ); 5.80 (m,
a
b
,
We have studied the scope of the Diels–Alder reaction
of the transient phenylenedioxy-ortho-quinodimethane 5,
issued from the thermal isomerisation of anthracene
epidioxide 3. We have then developed a very mild
preparation of naphthalene derivatives by triethylamine-
catalysed cleavage of the corresponding adducts. This
method allows the synthesis of acid-sensitive compounds
and offers certain advantages over the classical method
using dibromo-ortho-quinodimethane 1, but seems lim-
ited to reactive dienophiles as quinones 10a,b or diben-
zoylethylene 11.
d
a
b
195.7 (2 C5O) ppm. Anal. calcd for C20H14O4 (318.0): C,
75.46; H, 4.43; O, 20.10. Found: C, 75.7; H, 4.6; O, 20.2.
4.3.3. Naphthalenequinone adduct 14b: general procedure
with 3 (0.2 g, 0.95 mmol) and 10b (0.20 g, 1.28 mmol,
1.35 equiv.)
Cream crystals, 65–70% yield, mp 271 8C (benzene).
IR (KBr): 1670 (C5O), 1240, 980, 950, 800, 745 cmꢀ1. UV
(THF),
1H NMR (CDCl3):
H-11); 6.80 (s, 4 H, H-1 to H-4); 7.20 (s, 4 H, H-7 to H-10);
7.50–8.00 (m, 4 H, 2 H- , 2 H- 52.8
). 13C NMR (CDCl3):
(2 C- ); 81.2 (C-6, C-11); 123.3, 124.5 (C-1 to C-4); 127.0
(2 C- ); 129.7, 130.2 (C-7 to C-11); 133.9 (C-6a, C-10a);
134.6, 134.8 (2 C- , 2 C- ); 149.0 (C-4a, C-12a); 195.2
l
max(log
e
): 385 (2.26); 295 (3.39); 278 (3.51) nm.
4. Experimental part
d
4.05 (m, 2 H, 2 H- ); 6.00 (m, 2 H, H-6,
a
4.1. General
g
d
d
a
b
Flash chromatography (FC): silica gel (Merck 60, 230–
400 mesh). TLC: Al-roll silica gel (Merck 60, F254). Mp:
Kofler hot bench. IR spectra (
297. UV spectra: Spectrometer Cary 15. 1H and 13C NMR
spectra (80 MHz and 20 MHz resp.): Varian FT 80A,
tetramethylsilane (TMS) as an internal standard. Micro-
analyses were carried out by the Laboratoire de micro-
g
d
n
in cmꢀ1): PerkinElmer
(2 C5O) ppm. Anal. calcd for C24H16O4 (368.4): C, 78.25;
H, 4.38; O, 17.37. Found: C, 78.3; H, 4.4; O, 17.2.
4.3.4. trans-2,3-Dibenzoylethylene adduct 15: general
procedure with 3 (0.5 g, 2.4 mmol) and 11 (0.65 g, 2.75 mmol,
1.16 equiv.)
´
analyses, Universite Paris-6, France.
Cream crystals from boiling cyclohexane, 65% yield, mp
210–211 8C. IR (KBr): 1670 (C5O), 1490, 1440 cmꢀ1. UV
4.2. Reagents and solvents
(THF),
244 (4.50) nm. 1H NMR (CDCl3):
1H, H- ); 5.75 (d, J = 0.9 Hz, 1 H, H-11); 5.79 (d, J = 1.7 Hz,
l
max(log
e
): 316 (2.38); 277.5 (3.55); 272.5 (3.55);
Usual solvents and PhCl were freshly distilled, dry Et2O
and benzene were distilled and stored over Na, CHCl3 was
distilled over P2O5 and kept over Na2CO3.
d
4.50 (dd, J = 1.7, 8.2 Hz,
a
1 H, H-6); 5.90 (dd, J = 0.9, 8.2 Hz, 1 H, H-a0); 6.73 (s, 4 H, H-1
to H-4); 7.21 (s, 4 H, H-7 to H-10); 7.30–7.70 (m, 6 Har);
7.90-8.10 (m, 4 Har). 13C NMR (CDCl3, partial data without
4.2.1. Preparation of the 9,10-epidioxy-9,10-
dihydroxyanthracene (3) [12b]
aromatic C between 125–139 ppm): d49.0, 53.3 (C-a
, C-a0);
To a solution of anthracene (4.0 g, 22 mmol) in CHCl3
80.2, 82.2 (C-6, C-11); 148.9, 150.7 (C-4a, C-12a); 195.6,
196.2 (2 C5O) ppm. Anal. Calcd for C30H22O4 (446.5): C,
80.70; H, 4.97; O, 14.33. Found: C, 80.5; H, 5.0; O, 14.3.
(600 mL) was added
a solution of hematoporphyrin
hydrochloride (50 mg) in EtOH (100 mL) and this solution
was irradiated with a halogen lamp whose light was
filtered through an aqueous solution of Na2CrO4 (20 g/L).
The anthracene disappearing was monitored by UV-
spectroscopy or TLC. The dye was discarded by the
addition of solid Na2CO3 and filtration. The solution was
then evaporated, the residue crystallised and washed in
EtOH and Et2O to give cream crystals of 3 (4.2 g, 84%).
4.3.5. Cyclopentenone adduct 16
A solution of 3 (0.5 g, 2.4 mmol) and distilled 12 (1.6 mL,
19.2 mmol, 8.1 equiv.) in benzene (250 mL) was refluxed
for 16 h. The solvent was evaporated to give a mixture of
adduct 16 and 9,10-anthraquinone. After purification by
column chromatography (SiO2, eluent CH2Cl2), 16 was
isolated (0.15–0.2 g, 20–30% yield).
4.3. Preparation of the adducts
Cream crystals, mp 228–229 8C (benzene). IR (KBr):
1740, 1485, 1240, 770 cmꢀ1. 1H NMR (CDCl3):
d
1.80–2.80
4.3.1. General procedure
(m, 4 H); 3.52, 3.60 (2 m, each 1 H, H-a
, H-a0); 5.32, 5.62
A solution of 3 (0.2 g, 0.95 mmol) and the dienophile (ca
1.2 equiv.) in chlorobenzene (20 mL) was heated under
reflux for 1 h. The solvent was then evaporated and the
(2 m, each 1 H, H-6, H-11); 6.76 (s, 4 H, H-1 to H-4); 7.21 (s,
4 H, H-7 to H-10). Anal. calcd for C19H16O3 (292.2): C,
78.06; H, 5.52. Found: C, 77.9; H, 5.7.