Synthesis of six-membered functionalized carbocyclic compounds by one-pot reaction of hydroquinone derivatives and dienes

Article abstract of DOI:10.1080/00397911.2010.516460

A general method for one-pot reaction of hydroquinone derivatives and dienes has been developed. The system of Pb3O4 in tetrahydrofuran- trifluoroacetic acid was found to play dual roles as oxidant for the generation of quinones in situ and as catalyst for the Diels-Alder cycloaddition, which makes the one-pot reaction efficient and easy to carry out. Using this method, a variety of six-membered functionalized carbocyclic compounds can be easily prepared in medium to excellent yields at room temperature. Copyright

Full text of DOI:10.1080/00397911.2010.516460

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Synthesis of Six-Membered
Functionalized Carbocyclic Compounds
by One-Pot Reaction of Hydroquinone
Derivatives and Dienes
Guang-Rong Cai a , Zhi Guan a & Yan-Hong He a
a School of Chemistry and Chemical Engineering, Southwest
University, Chongqing, China
Version of record first published: 11 Jul 2011.
To cite this article: Guang-Rong Cai, Zhi Guan & Yan-Hong He (2011): Synthesis of Six-Membered
Functionalized Carbocyclic Compounds by One-Pot Reaction of Hydroquinone Derivatives and Dienes,
Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic
Chemistry, 41:20, 3016-3025
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Synthetic Communications1, 41: 3016–3025, 2011
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2010.516460
SYNTHESIS OF SIX-MEMBERED FUNCTIONALIZED
CARBOCYCLIC COMPOUNDS BY ONE-POT REACTION
OF HYDROQUINONE DERIVATIVES AND DIENES
Guang-Rong Cai, Zhi Guan, and Yan-Hong He
School of Chemistry and Chemical Engineering, Southwest University,
Chongqing, China
GRAPHICAL ABSTRACT
Abstract A general method for one-pot reaction of hydroquinone derivatives and dienes has
been developed. The system of Pb3O4 in tetrahydrofuran–trifluoroacetic acid was found to
play dual roles as oxidant for the generation of quinones in situ and as catalyst for the
Diels–Alder cycloaddition, which makes the one-pot reaction efficient and easy to carry
out. Using this method, a variety of six-membered functionalized carbocyclic compounds
can be easily prepared in medium to excellent yields at room temperature.
Keywords Diels–Alder reaction; hydroquinone derivatives; lead tetroxide; one-pot
reaction; oxidation
INTRODUCTION
Quinones are the most useful pericyclic materials for Diels–Alder reactions,
especially for the construction of six-membered functionalized carbocyclic com-
pounds,[1–3] and during the past several decades studying quinones as dienophiles
in the reaction has produced dramatic results.[4–6] However, quinones possessing
electron-withdrawing groups are difficult to isolate and decompose readily under
air,[5] water,[5] and some Lewis acid catalysis.[7] Hence, it is favorable to take advan-
tage of a suitable reagent and carry out the one-pot reaction of quinones generated in
situ, followed by Diels–Alder reaction with dienes. In this field, some studies of lim-
ited scope concerning the use of Ag2O,[8–14] Pb(OAc)4,[2] MnO2,[15,16] PhI(OAc)2,[4,17]
and electrochemical oxidation[7] have been reported. However, in most
methods the reagents were used only as oxidants to convert hydroquinone
[18]
PbO2,
Received August 10, 2009.
Address correspondence to Yan-Hong He, School of Chemistry and Chemical Engineering,
Southwest University, Chongqing, 400715, China. E-mail: heyh@swu.edu.cn
3016

ONE-POT REACTION OF HYDROQUINONES AND DIENES
3017
derivatives into corresponding quinones in situ. If a cheap and readily available
reagent can play dual roles as oxidant for the generation of quinones and as catalyst
for subsequent Diels–Alder cycloaddition in one pot, the result will be a nearly ideal
process in terms of both efficiency and simplicity. In our study of the synthesis of
functionalized carbocyclic compounds by a one-pot reaction of hydroquinone deri-
vatives and dienes, we found that the system of Pb3O4 in tetrahydrofuran (THF)
with a small amount of trifluoroacetic acid (TFA) not only can oxidize hydro-
quinone derivatives into the corresponding quinones in situ but also can catalyze
the following Diels–Alder reaction in one pot. It has been known that Pb3O4 can oxi-
dize hydroquinones into quinones,[19] but its catalytic activity for the Diels–Alder
reaction to our knowledge has not been reported. Therefore, we now report the dual
roles of Pb3O4 in one-pot reactions of hydroquinone derivatives and dienes.
RESULTS AND DISCUSSION
As previously reported,[19] Pb3O4 is an efficient oxidant for the conversion of
hydroquinones into corresponding quinones. We observed that 2,3-dicyanhydroqui-
none (1) could be quickly oxidized into quinone 2 quantitatively by Pb3O4 in THF=
TFA (20:1) at room temperature (Scheme 1). Therefore, we decided to use Pb3O4 in
one-pot reactions of hydroquinones and dienes to generate quinones in situ. In our
initial investigation to choose a suitable solvent for one-pot reaction of 2,3-
dicyanhydroquinone (1) and isoprene in the presence of Pb3O4 (Scheme 1), we com-
pared toluene, CH2Cl2, and acetone. They gave product 3 in disappointing yields,
probably because 2,3-dicyanhydroquinone (1) has poor solubility and Pb3O4 has
low dispersal in these solvents. However, when the solvent was THF, the formation
of product 3 was observed at a dramatic rate and in satisfactory yield.
To prove whether Pb3O4 can catalyze the subsequent Diels–Alder reaction in
one pot, the reaction of quinone 2 and isoprene was conducted at room temperature
under different conditions (Scheme 1, Table 1). The Diels–Alder reaction in pure
THF took a long time and gave the product 3 in tiny yield (entry 1, Table 1). When
THF=TFA was used, the rate and yield of the reaction improved somewhat (entries 2
and 3, Table 1). However, when treatment involved Pb3O4 in THF, it provided the
Scheme 1. Oxidation of 2,3-dicyanhydroquinone (1) and one-pot reaction of 1 and isoprene.

3018
G.-R. CAI, Z. GUAN, AND Y.-H. HE
Table 1. Diels–Alder reaction between quinone 2 and isoprene under different conditions at rt
Entry
Reaction condition
Time (h)
Yield of 3 (%)a
1
2
3
4
5
6
7
8
9
THF
THF-TFA (33:1)
24
16
16
16
16
16
5
5
35
37
58
62
65
78
80
80
THF-TFA (20:1)
Pb3O4 (0.2 eq), THF
Pb3O4 (0.4 eq), THF
Pb3O4 (0.8 eq), THF
Pb3O4 (0.2 eq), THF-TFA (33:1)
Pb3O4 (0.2 eq), THF-TFA (20:1)
Pb3O4 (0.2 eq), THF-TFA (10:1)
3
3
aRefers to yield of isolated product after chromatography.
product in medium yields (entries 4–6, Table 1). Interestingly, when the combined
system of Pb3O4 and THF=TFA was employed, the product was obtained in good
yields (entries 7–9, Table 1). The experiments clearly showed that both Pb3O4
and TFA can catalyze the Diels–Alder reaction of quinone 2 and isoprene, but
Pb3O4 is more efficient than TFA. The best chemical yield and rate were obtained
when both Pb3O4 and TFA were present in the system. Thus, taking into account
the consumption of an equimole of Pb3O4 as oxidant for the generation of quinones
and 0.2 equimoles of Pb3O4 as catalyst for the following Diels–Alder reaction, we
decided to use 1.2 equimoles of Pb3O4 in a one-pot reaction in the presence of
THF=TFA (20:1).
In the present procedure, the reaction was easy to carry out under the system of
Pb3O4 (1.2 eq) in THF-TFA (20:1) at room temperature. A variety of hydroquinone
derivatives and different dienes underwent the one pot reaction smoothly to afford
corresponding functionalized carbocyclic compounds in medium to good yields
(55%–80%) (Table 2). This one-pot method was also applicable to catechol derivative
25, which directly gave the isomerized adduct 26 in excellent yield of 94% in 2.5 h
(entry 12 in Table 2, Scheme 2). Some unstable resultant adducts were involved
because of easy aromatization (entries 2, 5, and 11, Table 2). In these cases, steady-
going aromatized products could be obtained directly after the one-pot reaction,
followed by routine workup and purification on silica gel. However, the one-pot
reaction of hydroquinone 4 and isoprene 5 gave the unstable adduct 27, which
was reduced without purification using Zn and HOAc[8] to give stable diketone 6
(entry 1 in Table 2, Scheme 3).
To our surprise, the one-pot reaction of 1-(2,5-dihydroxyphenyl) ethanone (12)
and 1,3-pentadiene (14) gave product 15 (entry 5, Table 2). In comparison with the
reaction of 12 and 8, which gave product 13 (entry 4, Table 2), it is reasonable to
assume that the cycloaddition had initially taken place at the acetyl-substituted dou-
ble bond to give adduct 28 because of the extra-activation by acetyl group
(Scheme 4). The formation of 15 may be through the 1,5-migration of the acetyl
group[20] and aromatization of 30. The mechanism of the 1,5-shift of acetyl has been
described by Cooper and Sammes.[21] They proposed that acetyl was rearranged by a
pathway involving prior enolization of one carbonyl group, followed by the
1,5-acetyl migration and next enolization of the remaining carbonyl group to

ONE-POT REACTION OF HYDROQUINONES AND DIENES
3019
Table 2. One-pot reaction of hydroquinones and dienes under the system of Pb3O4 (1.2 eq) in THF-TFA
(20:1) at rt
Entry
1
Hydroquinone
Diene
Product
Time (h)
Yield (%)a
6
80
2
3
7.5
3
64
57
4
5
6
7
3
6
3
3
65
55
61
75
8
9
3
3
3
75
80
80
10
11
4
75
(Continued )

3020
G.-R. CAI, Z. GUAN, AND Y.-H. HE
Table 2. Continued
Entry
12
Hydroquinone
Diene
Product
Time (h)
2.5
Yield (%)a
94
aRefers to yield of isolated product.
produce quinol 15 (Scheme 4). An alternative explanation for the formation of 15
was proposed as sequential reactions of retro-Diels–Alder=Diels–Alder=aromatiza-
tion (Scheme 5). Although cycloaddition of 2-acetyl-1,4-benzoquinone with diene
is known to favor addition across the 2,3 p-p bond to initially form adduct 28, with
the acetyl group occupying one of the angular positions, the reversibility of the
Diels–Alder reaction and aromatization of less favorable adduct 31 can shift the
equilibrium toward the formation of 15. However, in comparison with the formation
of adduct 13 (entry 4, Table 2), diene 8 is more sterically hindered than diene 14, and
it should be preferable to attack 2-acetyl-1,4-benzoquinone on the non substituted
double bond than 14, but only adduct 13 was obtained as an acetyl-substituted
double-bond addition product. We therefore prefer the mechanism of 1,5-shift of
acetyl to sequential reactions. No rearrangement of adduct 13 could be explained
Scheme 2. One-pot reaction of catechol 25 and diene 8.
Scheme 3. One-pot reaction of 4 and 5 and reduction of adduct 27.
Scheme 4. Proposed 1,5-acetyl shift pathway.

ONE-POT REACTION OF HYDROQUINONES AND DIENES
3021
Scheme 5. Proposed mechanism of sequential reactions.
Scheme 6. One-pot reaction of 18 and 5.
because the acetyl group migration depends on the substituents of diene.[21,22] Besides,
the tricyclic compound 13 might be more stable than the bicyclical compound 28. We
tried to recognize some intermediates for the proposed mechanisms but failed.
In addition, it is notable that the complete regioselectivity was observed in
adducts from one-pot reactions of electron-withdrawing group substituted hydroqui-
nones and dienes. All the electron-withdrawing groups including carboxylate, acetyl,
and nitrile activated the connected double bonds of corresponding quinones, and
different dienes were added to these electron-deficient double bonds except for
2,3-dicarboxylate hydroquinone 23 (entry 11, Table 2) because of steric hinderance.
Each reaction gave a single adduct from NMR. However, electron-donating groups
such as methyl and chlorine caused the connected double bonds of corresponding
quinones to be inactive, and the addition exclusively took place on the nonsubstituted
double bonds. The one-pot reaction of 2-methylbenzene-1,4-diol 7 and vinylcyclo-
hexene 8 gave the single aromatized product 9 (entry 2, Table 2). The regioselectivity
is in agreement with the previous report by Stojanac and coworkers.[23] Nevertheless,
hydroquinone 18 and isoprene 5 gave a 1:1 mixture of 19a and 19b from NMR, and
these compounds were not able to be separated by flash chromatography (Scheme 6).
CONCLUSION
In summary, we have developed a synthetic application of one-pot reactions of
hydroquinone derivatives and dienes in the presence of Pb3O4 and THF-TFA. In this
transformation, cheap and readily available reagent Pb3O4 plays important roles not

3022
G.-R. CAI, Z. GUAN, AND Y.-H. HE
only as an efficient oxidant for the generation of quinone derivatives in situ, but also
as an excellent catalyst for the following Diels–Alder reaction. The dual roles of
Pb3O4 in one pot make the reaction efficient and easy to carry out. Using this
method, different hydroquinone derivatives and dienes can be efficiently converted
into six-membered functionalized carbocyclic compounds in medium to excellent
yields in a short reaction time at room temperature.
EXPERIMENTAL
General Methods
1H NMR (300 MHz) and 13C NMR (75 MHz) spectra were recorded on a
Bruker AV-300 spectrometer with tetramethysilane (TMS) as an internal standard.
The chemical shifts (d) are given in parts per million (ppm), and the coupling con-
stants (J) are in hertz (Hz). Electospray ionization–high-resolution mass specto-
scopic (ESI-HRMS) spectra were recorded on a BioTOF Q spectrometer. Melting
points were determined on a X-4 digital display micromelting-point apparatus and
were uncorrected. Unless otherwise noted, all reagents were obtained from commer-
cial suppliers and were used without further purification. Organic solvents used were
dried by standard methods when necessary. All reactions were monitored by thin-
layer chromatography (TLC) with Haiyang GF254 silica-gel plates. Flash column
chromatography was carried out using 200 to 300-mesh silica gel at increased
pressure.
Typical Procedure for One-Pot Reaction of Hydroquinones and
Dienes: 1,4,4a,5,8,8a-Hexahydro-6-methyl-1,4-dioxonaphthalene-
4a,8a-dicarbonitrile (3)
Pb3O4 (605 mg, 0.88 mmol), F3CCO2H (0.25 mL), and isoprene (3.0 mmol)
were added to a solution of 2,3-dicyanhydroquinone 1 (100 mg, 0.63 mmol) in
THF (5 mL). The reaction mixture was stirred at rt for 3 h and then filtered. The fil-
trate was concentrated under reduced pressure, and the residue was purified by flash
chromatography (petroleum ether=ethylacetate 5:1) to provide compound 3 (106 mg,
80%) as white crystals. mp. 140–142 ꢀC; 1H NMR (CD3COCD3) d 7.19 (s, 2H), 5.54
(brs, 1H), 2.94–3.04 (m, 2H), 2.65–2.77 (m, 2H), 1.78 (s, 3H); 13C NMR
(CD3COCD3) d 187.5, 187.1, 139.1, 139.0, 130.9, 116.8, 116.5 (ꢁ2), 52.7, 52.2,
33.4, 30.1, 30.0; HRMS (ESI) calcd. for [M þ Na]þ C13H10N2O2Na: 249.0634;
found: 249.0652.
Spectroscopic Data for Compounds 11, 13, 15, 20, 21, 22, and 26
Ethyl 1,2,3,4,4a,4b,5,8,8a,9-decahydro-5,8dioxophenanthrene-8a-
carboxylate (11). Yellow oil; 1H NMR (CDCl3) d 6.75 (dd, 2H, J ¼ 10.5 Hz,
J ¼ 10.2 Hz), 5.32 (brs, 1H), 4.29–4.22 (m, 2H), 3.76–3.74 (m, 1H), 2.98 (d,
1H, J ¼ 12.9 Hz), 2.72 (m, 1H), 2.19 (m, 1H), 2.02–1.97 (m, 2H), 1.75 (d, 2H,
J ¼ 11.7 Hz), 1.43–1.36 (m, 2H), 1.29–1.27 (m, 2H), 1.24 (m, 3H); 13C NMR (CDCl3)

ONE-POT REACTION OF HYDROQUINONES AND DIENES
3023
d 197.9, 197.3, 169.8, 141.2, 139.7, 139.0, 114.7, 63.5, 62.3, 47.1, 42.1, 36.5, 33.4, 28.4,
27.2, 20.5, 14.1. HRMS (ESI) calcd. for [M]þ C17H20O4þ: 289.1395; found: 289.1364.
10a-Acetyl-5,6,7,8,10,10a-hexahydrophenanthrene-1,4(4aH,4bH)-dione
(13). Yellow oil; 1H NMR (CDCl3) d 6.83 (d, 1H, J ¼ 9.9 Hz), 6.60 (d, 1H,
J ¼ 10.2 Hz), 5.29 (brs, 1H), 3.72 (d, 1H, J ¼ 6.7 Hz), 2.87–2.71 (m, 2H), 2.32 (s,
3H), 2.23–2.18 (m, 1H), 2.03–1.98 (m, 2H), 1.83–1.73 (m, 3H), 1.44–1.35 (m, 2H),
1.24–1.20 (m, 1H); 13C NMR (CDCl3) d 204.5, 200.0, 198.1, 141.4, 139.3, 137.7,
115.5, 67.9, 45.7, 42.6, 38.7, 36.3, 28.6, 27.4, 19.7; HRMS m=z (ESI) calcd. for
[M]þ C16H18O3þ: 259.1289; found: 259.1275.
1-(1,4-Dihydro-5,8-dihydroxy-1-methylnaphthalen-6-yl)ethanone (15).
1
Yellow crystals, mp 162–164 ꢀC; H NMR (CDCl3) d 7.00 (s, 1H), 5.97–5.86 (m,
2H), 3.71 (m, 1H), 3.40–3.14 (m, 2H), 2.57 (s, 3H), 1.26 (d, 3H, J ¼ 6.6 Hz); 13C
NMR (CDCl3) d 203.8, 155.0, 144.7, 132.3, 131.6, 130.8, 120.9, 116.6, 111.8, 29.0,
26.7, 25.0, 21.6; HRMS (ESI) calcd. for [M ꢂ H]þ C13H13O3: 217.0859; found:
217.0867.
1,2,3,4,4a,4b,5,8,8a,9-Decahydro-5,8-dioxophenanthrene-8a-carbonitrile
1
(20). White crystals; mp 215–217 ꢀC. H NMR (CDCl3) d 6.98 (s, 2H), 5.45 (brs,
1H), 3.01 (m, 1H), 2.85–2.67 (m, 2H), 2.37–2.32 (m, 1H), 1.87–1.77 (m, 2H), 1.59
(d, 2H, J ¼ 10.1 Hz), 1.36–1.23 (m, 4H); 13C NMR (CDCl3) d 187.6, 185.2, 140.2,
138.9, 136.6, 115.9, 113.6, 44.5, 34.5, 31.6, 27.5, 27.2, 26.8, 26.5, 26.0.
1,4,4a,5,8,8a-Hexahydro-5-methyl-1,4-dioxonaphthalene-4a,8a-dicarbo-
1
nitrile (21). White crystals; mp 140-142 ꢀC. H NMR (CD3COCD3) d 7.15 (s, 2H),
5.73–5.85 (m, 2H), 2.79–3.12 (m, 3H), 1.42 (d, 3H, J ¼ 7.4 Hz); 13C NMR
(CD3COCD3) d 188.3, 187.2, 140.6, 138.4, 129.5, 121.4, 117.0, 116.4, 55.1, 54.9,
36.5, 30.8, 17.1; HRMS m=z (ESI) calcd. for [M þ Na]þ C13H10N2O2Naþ:
249.0634; found: 249.0631.
1,4,4a,4b,5,6,7,8,10,10a-Decahydro-1,4-dioxophenanthrene-4a,10a-
dicarbonitrile (22). White crystals; mp 173–175 ꢀC. 1H NMR (CD3COCD3) d 7.30
(s, 2H), 5.52 (brs, 1H), 2.71–2.14 (m, 3H), 1.82–1.83 (m, 2H), 1.25–1.65 (m, 6H); 13
C
NMR (CD3COCD3) d 188.8, 186.6, 141.5, 140.1, 137.4, 117.4, 116.9, 114.5, 56.8,
44.7, 36.0, 32.6, 29.8, 28.5, 28.0, 27.2; HRMS (ESI) calcd. for [M þ Na]þ
C16H14N2O2Na: 289.0947; found: 298.0954.
Ethyl 2,4a,4b,5,6,7,8,10-octahydro-1-hydroxy-2-oxophenanthrene-4a-
1
carboxylate (26). Yellow oil; H NMR (CDCl3) d 6.89 (d, 1H, J ¼ 9 Hz), 6.52 (d,
1H, J ¼ 9 Hz), 5.34 (brs, 1H), 4.15 (q, 2H, J ¼ 10.15), 3.39–3.14 (m, 2H), 2.97–2.90
(m, 1H), 2.25–2.06 (m, 2H), 1.84–1.73 (m, 4H), 1.50–1.25 (m, 2H), 1.20 (t, 3H);
13C NMR (CDCl3) 180.6, 170.6, 149.9, 144.4, 140.8, 128.2, 125.6, 114.4, 62.4,
56.3, 48.7, 36.5, 30.2, 29.7, 26.7, 25.5, 14.1; HRMS (ESI) calcd. for [M þ Na]þ
C17H20O4Na: 311.1253; found: 311.1262.
ACKNOWLEDGMENT
Financial support from the Scientific Research Foundation for the Returned
Overseas Chinese Scholars of the State Education Ministry, the High-Tech Training

3024
G.-R. CAI, Z. GUAN, AND Y.-H. HE
Fund of Southwest University (XSGX0601), and the Doctoral Fund of Southwest
University (SWNUB2005012) is gratefully acknowledged.
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