Synthesis of new derivatives of a representative o-quinone scaffold by reduction at the electrode

Article abstract of DOI:10.1016/j.tet.2012.05.042

The concomitant electrochemical reduction of 9,10-phenanthrenequinone and benzenediazonium tetrafluoroborate, under constant potential conditions (-0.5 V vs Ag/Ag⁺), has been performed in different organic solvents. An interesting entry to new C-C radical coupling products is here described. Another cathodic pathway where the anion radical intermediate acts as an EGB is also described. The electrochemical behaviour of both systems and mechanistic proposals are given.

Full text of DOI:10.1016/j.tet.2012.05.042

Tetrahedron 68 (2012) 5979e5983
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Synthesis of new derivatives of a representative o-quinone scaffold by reduction
at the electrode
,
a
a
a
b,
*
Belen Batanero a , Fructuoso Barba , Fernando Ranz , Isidoro Barba , Michail N. Elinson
*
a
ꢀ
ꢀ
Department of Organic Chemistry, University of Alcala, 28871 Alcala de Henares, Madrid, Spain
b N.D. Zelinsky Institute of Organic Chemistry, Leninsky prospect 47, 119991 Moscow, Russia
a r t i c l e i n f o
a b s t r a c t
Article history:
The concomitant electrochemical reduction of 9,10-phenanthrenequinone and benzenediazonium tet-
rafluoroborate, under constant potential conditions (ꢀ0.5 V vs Ag/Agþ), has been performed in different
organic solvents. An interesting entry to new CeC radical coupling products is here described. Another
cathodic pathway where the anion radical intermediate acts as an EGB is also described. The electro-
chemical behaviour of both systems and mechanistic proposals are given.
Received 22 February 2012
Received in revised form 24 April 2012
Accepted 11 May 2012
Available online 18 May 2012
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Cathodic reduction
9,10-Phenanthrenequinone
Hydrogen abstraction
Radical coupling
Diazonium salt
1. Introduction
should be mentioned that after a common initial electrochemical
step, the final obtained products were not always the expected ones
In the field of the organic electrosynthesis o-quinones have re-
ceived poor attention in spite of the interesting results they have
provided, as for instance the enediol diester formation1 or the ac-
ylation reactions which, depending on the acylating agent, can
produce the diacylated derivative or a diketopinacol diester.2 o-
Quinones have also been converted into 1,3-dioxoles through
a simple cathodic reduction in dichloromethane.3 More recently,
preparative scaled electroreduction of quinones in the presence of
diazonium salt (which was also reduced) under potentiostatic
conditions and working at the first voltammetric peak of these
systems, afforded hydroxycarboxamides, cyanomethylated de-
rivatives or 1,2-dichloroethyl compounds depending on the solvent
employed, DMF, acetonitrile or 1,2-dichloroethane, respectively.4
The prospect and potential of this concomitant reduction
pathway has been now studied with the aim to synthesize new
coupling products by employing other organic solvents, such as
chloroform, dichloromethane, chloroacetonitrile, acetone, buta-
none or ethyl acetate. In all cases 9,10-phenanthrenequinone has
been chosen as representative o-quinone scaffold substrate, and it
because with acetone and butanone as solvents the reduction
proceeds, even in absence of diazonium salt, through an ionic
electrocatalytic pathway.
2. Results and discussion
The general reaction mechanism of the concomitant reduction
of o-quinones and diazonium salts, is indicated in Scheme 1.
+ e-
Solvent
.
+
Solvent
OH
Ph
H
Ph
Ph
O
N
N
-N2
O
O
O
O
+ e-
-0.5V
.
Solvent
+ H+
S
.
Scheme 1.
Cyclic voltammetry of 9,10-phenanthrenequinone using aprotic
organic solvents/tetraalkylammonium salts (solvent-supporting
electrolyte [SSE] systems) shows (Fig. 1) two reduction peaks, each
corresponding to 1 F/mol process.
* Corresponding authors. Tel.: þ34 918852517; fax: þ34 918854686 (B.B.); tel.:
þ7 499 137 3842; fax: þ7 499 135 5328 (M.N.E.); e-mail addresses: belen.bata-
nero@uah.es (B. Batanero), elinson@ioc.ac.ru (M.N. Elinson).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2012.05.042

5980
B. Batanero et al. / Tetrahedron 68 (2012) 5979e5983
NC
O
NC
O
O
Cl
CN
Cl
CN
+ e-
- 0.5V
O
O
2c (70%)
O
NC
Scheme 4.
2.2. Reduction in chloroform as solvent
The electroreduction of 1 in chloroform/tetraalkylammonium
salt as SSE, at ꢀ0.5 V(vs Ag/Agþ), in the absence of the diazonium
salt, produced an intense-red solution corresponding to the for-
mation of the anion radical. After 1 F/mol charge was passed
through the cell the current decreased and the starting quinone
was recovered after the work-up (by an electron transfer to the
oxygen in air).
However, when benzenediazonium salt was simultaneously
reduced with 1, the electrolysis provided the expected radical
coupling product 3 in 40% yield (Scheme 5).
Fig. 1. Cyclic voltammogram of
1
in CH2Cl2/Bu4NBF4. 100 mV/s. Epc1¼ꢀ0.53 V,
Epc2¼ꢀ0.94 V (vs Ag/Agþ). Pt cathode.
2.1. Reduction in chloroacetonitrile as solvent
The electrolysis of 9,10-phenanthrenequinone (1) in ClCH2CN at
controlled ꢀ0.5 V (vs Ag/Agþ) potential provides 2-chloro-2-(9,10-
dihydro-9-hydroxy-10-oxophenanthren-9-yl) acetonitrile (2a) in
67% yield through the quinone anion radical formation. Simulta-
neously, the diazonium salt is reduced to a diazenyl radical that
loses molecular nitrogen evolving to a phenyl radical, which ab-
stracts a hydrogen atom from the solvent, chloroacetonitrile, pro-
ducing benzene and a chlorocyanomethyl radical. Final coupling of
chlorocyanomethyl radical with the quinone anion radical pro-
duces 2a after protonation during the work-up (Scheme 2). 10-
Hydroxy-10-phenylphenanthren-9(10H)-one4 was obtained as
a side product.
Cl
Cl
Cl
OH
O
O
O
O
O
.
.
CCl3
+ e-
+ H+
1
3a (40%)
Scheme 5.
Cl
CN
+ e-
-N2
Ph
Ph
N
N
O
Ph
Cl
H
+
Cl
O
CN
OH
One could postulate, due to the acidity of the chloroform, the
proton abstraction by the anion radical of the quinone (EGB) to
provide the trichloromethyl anion that subsequently adds to the
carbonyl group of a new starting molecule. However this should be
ruled out because the trichloromethyl anion is known to de-
compose, by chloride elimination, to the dichlorinated carbene. On
the other hand, electrolysis performed in the absence of diazonium
salt did not produce any yield on 3a.
It has been observed that when CHCl3 is stabilized with EtOH
(instead of amylenes), the electrolysis of 1, in the absence of di-
azonium salt, affords an unexpected product 3b in good yield
(Scheme 6). This yield is even increased to 87% when EtOH (up to
5%) is added to the catholyte solution.
OH
O
O
Ph
CN
Cl
CN
+ H+
+
(10%)
_
2a (67%)
Scheme 2.
1
When 1 is reduced in the absence of the diazonium salt, working
at the same electrode potential, the charge consumption of the
electrolysis corresponded to a 2 F/mol process. In this case the
double O-cyanomethylated product 2b was obtained in 90% yield. A
nucleophilic substitution takes place from the anion radical to the
solvent providing an alkoxy radical5 easily reduced to the alkoxide
anion (see Scheme 3) that finally attacks a new solvent molecule.
HO
COOEt
O
O
+ e-/-0.5V
CHCl3/EtOH
NC
O
CN
O
NC
3b
1
O
O
O
O
Scheme 6.
Cl
CN
Cl
CN
+ e-
SN
The proposed electrochemical pathway to explain the formation
of 3b is indicated in Scheme 7. The synthesis of 3b from 1 has al-
ready been described6 by employing a phosphonium salt in the
presence of lithium ethoxide.
2b (90%)
Scheme 3.
The easy reduction of alkoxy radicals7 has already been de-
scribed in Scheme 3, when chloroacetonitrile is employed as sol-
vent a charge consumption corresponding to a 2 F/mol process is
achieved at -0.5 V. Similarly, the electrolysis of 1 in CH2Cl2 at the
same working potential, in the presence of trifosgene as
1,4-Naphthoquinone and p-benzoquinone behave similarly at
the electrode. In this cases, even in the presence of the diazonium
salt, double O-cyanomethylation occurs, being 2c the main
obtained product (Scheme 4).

B. Batanero et al. / Tetrahedron 68 (2012) 5979e5983
5981
Pearson:9 ‘the hydrogen abstraction in methyl acetate occurs in the
acetyl group easier than in the methoxy group, due to the higher
resonance extension of the obtained radical in the former process’.
Scheme 7.
Scheme 10.
electrophile, proceeded with a charge consumption of 2 F/mol to
get the carbonate 3c in 90% yield (see Scheme 8). In the absence of
trifosgene, after the first electron transfer, the current falls down. A
second electron charge is circulated only if stoichiometric electro-
phile is added to the anion radical solution.
2.5. Reduction in acetone or butanone as solvents
The electrolysis of 1 in acetone, at the first reduction potential of
ꢀ0.5 V (vs Ag/Agþ), produces the red colouration of the typical anion
radical solution. Before any diazonium salt is added, decolouration
of that solution indicated consumption of this intermediate. Un-
expected products, as confirmed by TLC, were obtained. The absence
of 1 in the reaction mixture, after a charge consumption of only 10%
of theoretical charge for a 1 F/mol process, indicated an electro-
catalytic reaction. The obtained products were identified as 10-
hydroxy-10-(2-oxopropyl)-9,10-dihydrophenanthren-9-one (6a)
(69% yield) and the corresponding bishemiketal (6b) as secondary
product (22% yield). The proposed pathway to explain their forma-
tion is presented in Scheme 11. The anion radical of the quinone
behaves as an electrogenerated base (EGB) towards the solvent,
producing a radical (traces) and the acetonyl anion, that is further
added to the carbonyl group of a new molecule of 1, in a chain re-
action process.
Scheme 8.
2.3. Reduction in dichloromethane as solvent
The electroreduction of 9,10-phenanthrenequinone (1) in
CH2Cl2, performed at the second reduction potential of this sub-
strate, was already reported by our group to produce 1,3-dioxoles.3
When 1 is reduced to the anion radical, in concomitance with an
arenediazonium salt, the expected dichloromethylated product 4
was obtained, but in low yield as shown in Scheme 9.
Cl
OH
O
O
O
Cl
.
.
+ e-
CHCl2
+ H+
1
-0.5V
4 (24%)
Scheme 11.
Scheme 9.
However, when two molecules of the acetonyl anion attack both
carbonyl groups of the same new molecule 1, a dianion is obtained.
Further cyclization to the five membered bishemiketal 6b (as
a mixture of four stereoisomers, where only the major one was
isolated), by cross-addition to the free carbonyl groups, takes place
as indicated in Scheme 12.
The formation of the dichloromethyl radical, by hydrogen ab-
straction to the solvent, is now more difficult than in the case of
chloroform,8 being the quinone mainly recovered after the
work-up.
2.4. Reduction in ethyl acetate as solvent
Acetone self-condensation products were not obtained, due to
the higher reactivity of the quinone carbonyl group or because this
reaction proceeds at the electrode surface, where is highest the
concentration of electroactive substrate.
Electrolysis performed in butanone as solvent conducted to
similar results. In this case 77% yield on 10-hydroxy-10-(2-
When the solvent was ethyl acetate, the expected CeC radical
coupling reaction took place, affording the three possible isomers,
obtained in the same ratio than number of hydrogen atoms were
able to be abstracted (summarized in Scheme 10), according with

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B. Batanero et al. / Tetrahedron 68 (2012) 5979e5983
A solution of 9,10-phenanthrenequinone (1) (1.0 mmol in 60 mL
of SSE) was electrolyzed at the constant potential of the first qui-
none reduction peak. The diazonium salt (1.0 mmol) was added, as
solid portions, to the cathodic compartment during the electrolysis
(2 h). The complete disappearance of the anion radical red col-
ouration in the cathode solutions (when the diazonium salt is
added) indicated the end of the electrolysis. Once the reduction was
finished, the solvent in the cathodic solution was removed under
reduced pressure. The residue was extracted with ether/water and
the organic phase dried over Na2SO4 and concentrated by evapo-
ration. The resulting products were purified by silica gel 60 (35e70
mesh) in a (30ꢂ3 cm) column, using mixtures CH2Cl2/Hex or
CH2Cl2/EtOH as eluents. Spectroscopic description of the new
obtained compounds is given below.
O
O
HO
OH
O
O
O
O
O
O
O
O
O
O
O
+
2
2
1
+
2
6b (22%)
Scheme 12.
oxobutyl)-9,10-dihydrophenanthren-9-one (7a) and the corre-
sponding bishemiketal (10% yield) were obtained.
Having in mind the EGB behaviour of the anion radical in-
termediate towards acetone or butanone, employed as solvents, 1
was reduced in dry acetonitrile. Once the anion radical was formed
at ꢀ0.5 V, stoichiometric amount of phenacyl bromide was added
to the catholyte solution under open air atmosphere (with the
electrochemical cell swich-off). After 12 h of stirring, the crude was
analyzed and the new main product isolated and spectroscopically
characterized as the spiroketoepoxide 8, which formation involves,
once again, an EGB behaviour of the anion radical intermediate, as
expected and indicated in Scheme 13.
3.1.1. 2-Chloro-2-(9,10-dihydro-9-hydroxy-10-oxophenanthren-9-yl)
acetonitrile (2a). (67% yield). Mp 170e172 ꢁC. IR (KBr)
n
¼3450,
2952, 2260, 1700, 1598, 1451, 1285, 1192, 1030, 769, 731, 622 cmꢀ1
1H NMR (300 MHz; CDCl3)
(ppm): 4.47 (bs, 1H), 4.70(s, 1H), 7.35-
7.50 (m, 3H), 7.62-8.0 (m, 5H).13C NMR (75.4 MHz, CDCl3)
: 51.4,
d
d
78.6, 113.3, 123.7, 124.8, 127.7, 127.9, 129.4, 129.5, 129.9, 130.4, 130.6,
133.0, 136.2, 136.9, 197.4. MS m/z (relative intensity) EI: 285(Mþþ2,
3), 283(Mþ, 8), 209(100), 180(30), 153(12). Anal. Calcd for C16 H10 Cl
N O2: C, 67.72; H, 3.53; N, 4.94. Found: C, 68.01; H, 3.42; N, 5.16.
3.1.2. 9,10-Di(cyanomethoxy) phenanthrene (2b). (90% yield). Mp
140e142 ꢁC. IR (KBr)
n
¼3064, 2955, 2245, 1601, 1449, 1328, 1114,
1069, 994, 752, 727 cmꢀ1 1H NMR (300 MHz; CDCl3)
(ppm): 5.0 (s,
4H), 7.72-7.98 (m, 4H), 8.24-8.30 (m, 2H), 8.70-8.78 (m, 2H).13C
d
NMR (75.4 MHz, CDCl3) d: 58.5,115.2,122.2,123.0,127.1,127.5,127.7,
129.5, 142.5. MS m/z (relative intensity) EI: 288(Mþ, 81), 248(100),
221(18), 195(22), 180(29), 152(19). Anal. Calcd for C18 H12 N2 O2: C,
75.0; H, 4.17; N, 9.72. Found: C, 74.77; H, 4.04; N, 10.02.
Scheme 13.
3.1.3. 1,4-Di(cyanomethoxy) naphthalene (2c). (70% yield). Mp
102e105 ꢁC. IR (KBr)
n
¼3071, 2920, 2252, 1634, 1600, 1468, 1278,
1247, 1102, 815, 771 cmꢀ1 1H NMR (300 MHz; CDCl3)
(ppm): 4.85
(s, 4H), 6.77(s, 2H), 7.46-7.58(m, 2H), 8.04e8.16 (m, 2H).13C NMR
d
3. Experimental section
(75.4 MHz, CDCl3) d: 54.2, 105.2, 115.0, 121.5, 126.3, 127.1, 148.1. MS
m/z (relative intensity) EI: 238(Mþ, 40), 198(100), 171(15), 158(13),
130(24), 102(27), 76(15). Anal. Calcd for C14 H10 N2 O2: C, 70.6; H,
4.20; N, 11.76. Found: C, 70.43; H, 4.02; N, 11.93.
Electrode reductions were performed using an Amel potentio-
stat Model 552 with electronic integrator Amel Model 721. Mass
spectra (EI, ionizing voltage 70 eV) were determined using
a THERMOFISHER ITQ-900 DIP-MSn mass-selective detector. IR
spectra of the compounds were recorded as dispersions in KBr or
NaCl films on a PerkineElmer FTIR spectrometer Spectrum 2000.
1H and 13C NMR spectra were recorded in CDCl3 on a Varian Unity
300 (300 MHz) spectrometer with tetramethylsilane (TMS) as the
internal standard. All melting points were measured on a Reichert
Thermovar microhot stage apparatus and are uncorrected. Ele-
mental analyses were performed on a PerkineElmer Model 240-B
analyzer.
3.1.4. 10-(Trichloromethyl)-10-hydroxyphenanthren-9(10H)-one
(3a). (40% yield). Mp 117e119 ꢁC. IR (KBr)
n
¼3443, 3064, 1691,
1600, 1452, 1057 cmꢀ1 1H NMR (300 MHz; CDCl3)
d
(ppm): 5.1 (bs,
1H), 7.36 (t, 2H, J¼7.6 Hz), 7.46 (t, 1H, J¼7.6 Hz), 7.6 (t, 1H, J¼8.1 Hz),
7.8 (t, 2H, J¼8.1 Hz), 7.9 (d,1H, J¼7.6 Hz). 13C NMR (75.4 MHz, CDCl3)
d: 83.8, 103.1, 122.9, 123.9, 127.5, 128.3, 128.5, 129.6, 130.4, 130.7,
132.0, 132.6, 136.0, 139.2, 196.9. MS m/z (relative intensity) IQ:
331(Mþþ5, 21), 329(Mþþ3, 64), 327(Mþþ1, 68), 295(7), 293(27),
291(38), 238(19), 210(100). Anal. Calcd for C15 H9 Cl3 O2: C, 54.96; H,
2.75. Found: C, 55.14; H, 2.99.
3.1. General electrochemical procedure
The electrolyses were carried out under an argon atmosphere
and potentiostatic (ꢀ0.5 V, vs Ag/Agþ) conditions (initial current of
100 mA) in a concentric cell with two compartments separated by
a porous (D4) glass frit diaphragm and equipped with a magnetic
stirrer. The temperature was maintained constant to 6 ꢁC with
a cryostat when diazonium salt was involved. A mercury pool was
used as the cathode (12 cm2) and a platinum plate as the anode
(4 cm2). A reference Ag/Agþ electrode was employed. The solvent-
supporting electrolyte system (SSE) was anhydrous ClCH2CN,
CHCl3 (stabilized with EtOH or amylenes), CH2Cl2, acetone, buta-
none or ethyl acetate containing 0.1 M tetrabutylammonium
tetrafluorborate.
3.1.5. Ethyl
10-hydroxyphenanthrene-9-carboxylate
(3b). (87%
yield). Mp 107 ꢁC [Lit.6 108e109 ꢁC]. 13C NMR (75.4 MHz, CDCl3)
d
:
14.4, 62.0, 101.5, 122.4, 122.8, 124.2, 124.9, 125.9, 126.8, 127.5, 129.4,
130.4, 133.6, 162.6, 172.8.
3.1.6. Phenanthro[9,10-d]-1,3-dioxol-2-one (3c). (90% yield). Mp
177e178 ꢁC. [Lit.10 178e179 ꢁC]. 13C NMR (75.4 MHz, CDCl3)
d: 119.1,
120.3, 123.6, 126.9, 128.0, 128.2, 136.0, 152.2.
3.1.7. 10-(Dichloromethyl)-10-hydroxyphenanthren-9(10H)-one
(4). (24% yield). Mp 129e131 ꢁC. IR (KBr)
¼3461, 3065, 2924, 1704,
1600, 1452, 1374, 1192, 1011, 729 cmꢀ1 1H NMR (300 MHz; CDCl3)
n

B. Batanero et al. / Tetrahedron 68 (2012) 5979e5983
5983
d
(ppm): 4.6 (bs,1H), 5.7 (s,1H), 7.3e7.5 (m, 3H), 7.6e7.9 (m, 5H). 13
NMR (75.4 MHz, CDCl3) : 77.1, 81.3, 123.5, 124.5, 127.7, 128.0, 128.6,
C
12), 209(100), 181(60), 152(43). Anal. Calcd for C18 H16 O3: C, 77.14;
H, 5.71. Found: C, 76.91; H, 5.87.
d
129.0, 129.8, 130.2, 134.3, 135.9, 137.3, 198.7. MS m/z (relative in-
tensity) EI: 294(Mþþ2, 2), 292(Mþ, 3), 209(100), 181(43), 165(14),
152(19). Anal. Calcd for C15 H10 Cl2 O2: C, 61.43; H, 3.41. Found: C,
61.29; H, 3.20.
3.1.14. 3-Benzoyl
(8). (43% yield). Mp 160 ꢁC [Lit.13 161e162 ꢁC]. IR (KBr)
1690, 1596, 1235, 745 cmꢀ1 1H NMR (300 MHz; CDCl3)
(ppm): 4.15
spiro[oxirane-2,90(100H)-phenanthren]-100-one
¼3058,
n
d
(s, 1H), 7.25-7.50 (m, 5H), 7.63(t, 1H, J¼7.7 Hz), 7.8(d, 1H, J¼7.9 Hz),
3.1.8. Ethyl
2-(9,10-dihydro-9-hydroxy-10-oxophenanthren-9-yl)
7.91 (d, 2H, J¼7.2 Hz), 7.96-8.04(m, 2H).13C NMR (75.4 MHz, CDCl3)
acetate (5a). (40% yield). Mp 79e81 ꢁC [Lit.11 82e83 ꢁC].
d: 62.8, 71.7, 123.4, 124.2, 124.3, 127.8, 128.7, 128.8, 129.6, 129.7,
129.8, 132.5, 132.6, 134.1, 135.1, 135.4, 136.7, 190.4, 190.5. MS m/z
3.1.9. Ethyl
acetate (5b). (15% yield). IR (KBr)
1598, 1450, 1369, 1237, 1063, 757 cmꢀ1 1H NMR (300 MHz; CDCl3)
(ppm): 1.8 (s, 3H), 2.05 (t, 2H, J¼5.8 Hz), 4.1 (m, 2H), 5.0 (bs, 1H),
7.3-7.4 (m, 3H), 7.6-7.9 (m, 5H).13C NMR (75.4 MHz, CDCl3)
: 20.8,
29.7, 59.9, 78.1, 123.3, 124.3, 126.0, 127.4, 128.4, 128.8, 129.4, 129.5,
135.2, 136.0, 137.4, 170.6, 203.1. MS m/z (relative intensity) EI:
296(Mþ, 40), 279(67), 252(12), 210(100), 209(53), 181(64), 152(16).
Anal. Calcd for C18 H16 O4: C, 72.97; H, 5.41. Found: C, 73.18; H, 5.62.
2-(9,10-dihydro-9-hydroxy-10-oxophenanthren-9-yl)
(relative intensity) EI: 326(Mþ, 20), 297(20), 221(100), 165(34).
n
¼3454, 3063, 2915, 1737, 1694,
4. Conclusion
d
d
The easy generation of the 9,10-phenanthrenequinone anion
radical at ꢀ0.5 V (vs Ag/Agþ) allows the synthesis of different
compounds, some of them now described for first time. Two pos-
sible mechanistic pathways are involved: (a) the concomitant re-
duction of the quinone with an arenediazonium salt that provides
radical coupling products, as in the case of chloroacetonitrile,
chloroform, dichloromethane or ethyl acetate, or (b) in absence of
diazonium salt, the anion radical behaves as an EGB towards phe-
nacyl bromide or solvents as acetone and butanone where an
electrocatalytic reaction is involved.
3.1.10. 1-(9,10-Dihydro-9-hydroxy-10-oxophenanthren-9-yl)
acetate (5c). (10% yield). Mp 100e102 ꢁC. IR (KBr)
¼3473, 3058,
2921, 1740, 1698, 1600, 1452, 1371, 1235, 1068 cmꢀ1 1H NMR
(300 MHz; CDCl3)
(ppm): 1.1 (d, 3H, J¼6.4 Hz), 1.8 (s, 3H), 4.1 (bs,
ethyl
n
d
1H), 5.0 (q, 1H, J¼6.4 Hz), 7.3-7.4 (m, 3H), 7.6-7.7 (m, 2H), 7.74(d,
2H, J¼8.1 Hz), 7.9(d, 1H, J¼8.1 Hz). 13C NMR (75.4 MHz, CDCl3)
d:
Acknowledgements
14.0, 20.7, 29.7, 75.1, 123.3, 124.2, 127.1, 127.2, 128.4, 128.6, 128.8,
130.2, 135.2, 136.2, 137.5, 169.4, 201.9. MS m/z (relative intensity)
EI: 296(Mþ, 73), 279(40), 237(18), 209(100), 181(76), 152(25),
87(12). Anal. Calcd for C18 H16 O4: C, 72.97; H, 5.41. Found: C,
72.82; H, 5.26.
B.B. thanks the Spanish Ministry of Economy and Competitivity
for the I3 Program financial support.
Supplementary data
3.1.11. 10-Hydroxy-10-(2-oxopropyl)-9,10-dihydrophenanthren-9-
one (6a). (69% yield). Mp 96 ꢁC [Lit.12 96e98 ꢁC]. MS m/z (relative
intensity) EI: 266(Mþ, 14), 209(100), 181(53), 152(57).
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tet.2012.05.042.
References and notes
3.1.12. Bishemiketal (6b). (Mixture stereoisomers 22% yield). Data
of the major one: Mp 180e181 ꢁC [Lit.12 179e180 ꢁC]. MS m/z
(relative intensity) EI: 324(Mþ, 11), 308(17), 307(100), 289(49),
1. Guirado, A.; Barba, F.; Tevar, A. Synth. Commun. 1984, 14, 333e338.
2. Guirado, A.; Barba, F.; Hursthouse, M. B.; Arcas, A. J. Org. Chem. 1989, 54,
3205e3206.
3. Batanero, B.; Barba, F. Org. Lett. 2005, 7, 2567e2569.
4. Batanero, B.; Saez, R.; Barba, F. Electrochim. Acta 2009, 54, 4872e4879.
5. Nonhebel, D. C.; Walton, J. C. In Free-radical Chemistry; Cambridge at the Uni-
versity: 1974; p 348.
246(13), 244(12), 231(5). 13C NMR (75.4 MHz, CDCl3)
d: 21.8, 27.7,
51.1, 91.8, 106.4, 123.2, 123.5, 127.0, 127.1, 127.2, 128.4, 128.6, 129.6,
135.6.
6. Litinas, K. E.; Nicolaides, D. N. J. Chem. Soc., Perkin Trans. 1: Organic and Bioorg.
1985, 429e435.
7. Baizer, M. M. In Organic Electrochemistry, 3rd ed.; Baizer, M. M., Lund, H., Eds.;
Marcel and Dekker: NY, 1991; p 434.
8. Bernardi, F.; Bottoni, A. J. Phys. Chem. A 1997, 101, 1912e1919.
9. Ferguson, K. C.; Pearson, J. T. Trans. Faraday Soc. 1970, 66, 910e919.
10. Hiyama, T.; Fujita, Sh.; Nozaki, H. Bull. Chem. Soc. Jpn. 1972, 45, 2797e2801.
11. Cameron, D. W. Aust. J. Chem. 1978, 31, 2259e2270.
12. Linko, R. V.; Belsky, V. K.; Varlamov, A. V.; Zaitsev, B. E.; Chernyshev, A. I. Russ.
Chem. Bull. Int. Ed. 2001, 50, 1625e1629.
3.1.13. 10-Hydroxy-10-(2-oxobutyl)-9,10-dihydrophenanthren-9-one
(7a). (77% yield). Mp 81e83 ꢁC. IR (KBr)
n
¼3444, 3062, 2922, 1708,
1690, 1598, 1452, 1100, 762, 727 cmꢀ1 1H NMR (300 MHz; CDCl3)
d
(ppm): 1.0 (t, 3H, J¼6.9 Hz), 2.9 (m, 2H), 2.8(d, 1H, J¼14.5 Hz),
3.0(d, 1H, J¼14.5 Hz), 5.1 (bs, 2H), 7.4e7.5 (m, 3H), 7.72(t, 1H,
J¼7.8 Hz), 7.78e7.8(m, 1H), 7.82e7.88(m, 1H), 7.93(d, 1H, J¼7.8 Hz),
8.0(d, 1H, J¼7.8 Hz). 13C NMR (75.4 MHz, CDCl3)
d: 7.2, 38.1, 54.5,
78.4, 123.0, 124.3, 125.9, 127.6, 128.5, 128.7, 129.1, 129.2, 129.3, 134.7,
13. Awad, W. I.; Salih, Z. S.; Aiube, Z. H. J. Chem. Soc., Perkin Trans. 1: Organic and Bio-
136.7, 139.6, 202.5, 208.0. MS m/z (relative intensity) EI: 280(Mþ,
Organic Chemistry 1977, 1280e1282.