Triphenylphosphane-mediated addition of dimethyl acetylenedicarboxylate to 1,2- and 1,4-benzoquinones: Synthesis of novel γ-spirolactones

Article abstract of DOI:10.1055/s-2000-8212

The zwitterionic intermediate, generated by the addition of triphenylphosphane to dimethyl acetylenedicarboxylate, undergoes facile addition to ortho- and para-quinones to afford highly functionalized novel unsaturated γ-spirolactones in moderate to high

Full text of DOI:10.1055/s-2000-8212

PAPER
1713
Triphenylphosphane-Mediated Addition of Dimethyl Acetylenedicarboxylate
to 1,2- and 1,4-Benzoquinones: Synthesis of Novel -Spirolactones
Vijay Nair,* J. Somarajan Nair, A. U. Vinod
Organic Chemistry Division, Regional Research Laboratory (CSIR), Trivandrum-695 019, India
Fax +91(471)491712; E-mail: gvn@csrrltrd.ren.nic.in
Received 28 May 2000; revised 22 July 2000
Dedicated to Professor Dr. Ivar Ugi in appreciation of his original contributions to organic chemistry
t
Bu
t
Bu
Abstract: The zwitterionic intermediate, generated by the addition
CO2Me
of triphenylphosphane to dimethyl acetylenedicarboxylate, under-
goes facile addition to ortho- and para-quinones to afford highly
functionalized novel unsaturated -spirolactones in moderate to
high yields.
O
O
+
CO2Me
OMe
(i)
t
Bu
t
Bu
O
CO2Me
O
O
Me
OMe
O
Key words: addition reactions, dimethyl acetylenedicarboxylate,
3
quinones, triphenylphosphane, spirolactones
(i) Ph3P/benzene, 80 °C, 4 h, 70%
Scheme 1
Phosphorus and its compounds have been extensively
used in organic synthesis.1 Organophosphanes have re-
ceived special attention and among the phosphanes, triph-
enylphosphane has emerged as the reagent of choice.2 Its
use as a catalyst in various isomerization reactions is well
In the 13C NMR spectrum of 3, the spirocarbon resonated
at = 83.3 ppm. The lactone and enone carbonyl carbons
appeared at = 160.6 and 190.1 ppm, respectively. Final
proof of the structure was discernible from the single crys-
tal X-ray analysis of the adduct 4.19 Similar results were
obtained with other o-quinones and these are summa-
rized in Table 1.
5
known.3 It has been shown that triphenylphosphane
adds to dimethyl azodicarboxylate to generate a zwitteri-
on, which serves as intermediate in the Mitsunobu reac-
tion and it has been trapped by propiolates to give
dihydropyrazole derivatives.6 Similarly, it has been
shown by Tebby7 13 that zwitterionic intermediates gener-
ated by the addition of triphenylphosphane to dimethyl
acetylenedicarboxylate (DMAD), dicyanoacetylene, and
dibenzoyl acetylene afford unique phosphorane deriva-
tives. It is also known that such zwitterionic intermediates
adds to benzaldehyde,14 -keto nitriles, and -keto esters15
to give -lactones. In the context of our interest in the cy-
cloaddition chemistry of o-quinones,16,17 especially the
addition of dipolar species to o-quinones,18 we undertook
an investigation of the addition of zwitterionic intermedi-
ates generated from triphenylphosphane and dimethyl
acetylenedicarboxylate to o-quinones. A preliminary re-
port on the studies resulting in a spirolactone synthesis has
already been published.19 Subsequently, we have expand-
ed these studies to include 1,4-quinones and our complete
results are presented here.
4-tert-Butyl-1,2-benzoquinone on reaction with DMAD
and triphenylphosphane afforded an inseparable mixture
1
of isomers 6a and 6b in 1:1 ratio. In the H NMR spec-
trum, the two tert-butyl groups resonated at = 1.17 ppm
and 1.25 ppm and two signals at = 77.2 ppm and 78.4
ppm were attributed to spirocarbons in the 13C NMR spec-
trum. The reaction of 1,2-naphthoquinone afforded a 1:1
mixture of spirolactones 7a and 7b. Compound 7a
showed absorptions in the IR spectrum at = 1795,1719,
1
and 1695 cm due to the lactone, ester, and benzoyl car-
1
bonyls. In the H NMR spectrum, the olefinic H-atoms
resonated at = 5.90 (d, 1 H, J = 10.6 Hz) and 6.91 (d, 1
H, J = 10.6 Hz) as two doublets. 7b showed IR absorp-
1
1
tions at = 1779, 1709, and 1681 cm . In the H NMR
spectrum, the olefinic H-atoms were discernible at
=
6.41 (d, 1 H, J = 11 Hz) and 7.50 (d, 1 H, J = 11 Hz) con-
firming an enone moiety.
Addition of the zwitterionic intermediate generated from
triphenylphosphane (50 mol%) and DMAD to 4,6-di-tert-
butyl-3-methoxy-1,2-benzoquinone afforded the spirolac-
tone 3 in 70% yield. The reaction can be represented as in
Scheme 1.
In continuation of the above investigations, we have also
studied the reactivity of p-quinones towards the zwitteri-
onic intermediate and the results are discussed in the fol-
lowing section. 1,4-Benzoquinone, when treated with
DMAD and 50 mol% of triphenylphosphane in benzene at
ambient temperature for 12 hours, afforded 11 in 88%
yield (Scheme 2).
The IR spectrum of 3 showed strong absorption at
= 1793 cm–1 and 1729 cm 1 due to the lactone and ester
1
carbonyls, respectively. In the H NMR spectrum, the
The structure of 11 was established by analytical and
spectroscopic methods. The IR spectrum of 11 showed a
three methoxycarbonyl H-atoms resonated at = 3.67
ppm as a singlet. The signals of the two methoxy groups
were observed at = 3.60 ppm and 4.29 ppm as singlets.
1
strong absorption at = 1774 cm , indicating the pres-
Synthesis 2000, No. 12, 1713–1718 ISSN 0039-7881 © Thieme Stuttgart · New York

1714
V. Nair et al.
Table 1 Addition of Dimethyl Acetylenedicarboxylate to 1,2-Quinones
PAPER
a
Entry
Quinone
Conditions
Product(s)
Yield (%)
t
t
Bu
Bu
O
Benzene
80° C
48 h
O
O
CO2Me
OMe
b
48
1
t
t
Bu
Bu
O
4
O
O
CO2Me
OMe
O
Benzene
80° C
1 h
78
2
O
O
O
5
O
t
O
Bu
CO2Me
CO2Me
OMe
O
Benzene
+
t
Bu
c
80° C
5 h
26
OMe
(1:1)
3
t
Bu
O
O
O
6b
O
6a
O
MeO
O
O
O
O
MeO2C
O
O
O
O
Benzene
80° C
4 h
OMe
+
46
46
55
4
5
CO2Me
(1:1)
7b
7a
CHPh2
O
CHPh2
CO2Me
O
Benzene
80° C
1.5 h
OMe
Ph2CH
O
O
Ph2CH
OMe
O
OMe
8
O
CO2Me
O
Benzene
80° C
1 h
6
OMe
O
O
9
O
a Isolated yield.
b Yield based on recovered quinone was 60%, see Ref. 19.
c Inseparable mixture.
ence of the lactone moiety. In the 1H NMR spectrum, the
methoxycarbonyl group was observed as a singlet at
= 3.73 ppm and the methoxy group adjacent to the lac-
tone carbonyl resonated at = 4.31 ppm. The four olefinic
H-atoms in the cyclohexadienone ring appeared as a mul-
tiplet between = 6.37 6.54 ppm. In the 13C NMR spec-
trum, the spirocarbon was discernible at = 76.9 ppm. A
mechanistic pathway for the formation of 11 involves the
initial generation of a zwitterionic intermediate from
triphenylphosphane and dimethyl acetylenedicarboxylate,
which then adds to quinone carbonyl to yield a betaine.
The betaine on subsequent cyclization leads to the spiro-
O
O
CO2Me
CO2Me
(i)
CO2Me
OMe
+
O
O
O
11
10
(i) PPh3,Benzene, RT, 12 h, 88%
(i) Ph3P/benzene, r.t., 12 h, 88%
Scheme 2
Synthesis 2000, No. 12, 1713–1718 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Triphenylphosphane-Mediated Addition of Dimethyl Acetylenedicarboxylate
1715
1H NMR: = 1.21 (s, 9 H, t-C4H9), 1.27 (s, 9 H, t-C4H9), 3.60 (s, 3
H, OCH3), 3.67 (s, 3 H, CO2CH3), 4.29 (s, 3 H, =COCH3), 7.12 (s,
1 H, =CH).
13C NMR: = 29.0, 29.8, 34.6, 35.0, 51.8, 60.3, 62.1, 83.3, 121.7,
127.6, 131.8, 140.0, 150.0, 152.3, 166.6, 190.1.
EIMS: m/z (%) = 392 (M+, 6), 349 (23), 348 (62), 333 (71), 301
(74), 271 (23), 245 (18), 143 (29) 115 (29), 91 (28), 59 (32), 57
(100), 44 (70).
O
CO2Me
Ph3P
CO2Me
+10
Ph3P
CO2Me
PPh3
O
MeO
MeO2C
CO2Me
O
O
7,9-Di-tert-butyl-3-methoxy-2,10-dioxo-1-oxaspiro[4.5]deca-
3,6,8-triene-4-carboxylic Acid Methyl Ester (4)
See Ref. 19 for the experimental, spectral, and single crystal X -ray
data.
O
O
O
11
-PPh3
O
O
O
Spiro[phenanthrenylene-1(2H), 3-methoxy-4-methoxycarbon-
ylfuran-2-one]-2-one (5)
OMe
PPh3
OMe
O
MeO
PPh3
OMe
To a mixture of 9,10-phenanthrenequinone (230 mg, 1.10 mmol)
and DMAD (172 mg, 1.21 mmol) in anhyd benzene (10 mL) at
80 °C was added Ph3P (145 mg, 0.55 mmol) and the mixture was
heated for further 1 h. The solvent was removed under reduced pres-
sure and the residue, after chromatographic separation on silica gel
using 80:20 hexanes/EtOAc gave 5 as a yellow solid (304 mg,
78%).
Scheme 3
lactone (Scheme 3). Similar spirolactones were obtained
with other 1,4-quinones and these results are presented in
Table 2
IR (KBr): = 1780 (OC=O), 1734 (CO2Me), 1707 (C=O), 1657
cm 1 (C=C).
1H NMR: = 3.40 (s, 3 H, CO2CH3), 4.36 (s, 3 H, =COCH3), 7.25
7.50 (m, 4 H, ArH), 7.69 7.75 (m, 1 H, ArH), 8.04 8.13 (m, 3 H,
ArH).
13C NMR: = 52.0, 60.4, 81.0, 123.3, 123.6, 124.1, 128.1, 128.1,
128.7, 129.3, 130.4, 131.3, 131.9, 135.7, 136.6, 149.2, 160.7, 166.4,
190.1.
In conclusion, we have exploited the reactivity of both
ortho- and para-quinones towards the zwitterionic inter-
mediate generated by the addition of triphenylphosphane
to DMAD. These investigations have resulted in a facile
synthesis of highly functionalized unsaturated spirolac-
tones. It is noteworthy that the unsaturated spirolactone
moiety is present in a number of biologically active natu-
ral products such as chlorothricin, kijanolide, and tetrano-
lide.20
Anal. calcd for C20H14O6: C, 68.57; H: 4.02. Found C, 68.82; H,
4.27.
7-tert-Butyl-3-methoxy-2,10-dioxo-1-oxaspiro[4.5]deca-3,6,8-
triene-4-carboxylic Acid Methyl Ester (6a) and 8-tert-Butyl-3-
methoxy-2,6-dioxo-1-oxaspiro[4.5]deca-3,6,8-triene-4-carboxy-
lic Acid Methyl Ester (6b)
Melting points were recorded on Toshniwal and Büchi melting
point apparatus and are uncorrected. IR spectra were recorded on
Perkin-Elmer-882 and Nicolet Impact 400D FT-IR spectrophotom-
eters. NMR spectra were recorded on Jeol EX-90, Bruker-300, and
Varian 500 NMR spectrometers. NMR spectra were obtained using
CDCl3 as the solvent and chemical shifts are given in scale with
TMS as the internal standard. J values are given in Hz. Mass spectra
were recorded on a Fisons GC-8000-MD-800 and AE1 MS-50-(IE)
mass spectrometers. Elemental analyses were obtained on a Perkin-
Elmer-2400 elemental analyzer. Purification by gravity column
chromatography was carried out using silica gel (100-200 mesh).
Hexanes and EtOAc were used as eluents. Dimethyl acetylenedicar-
boxylate was purchased from Aldrich Chemical Co. and was used
without further purification.
To
a
mixture of 4-tert-butyl-1,2-benzoquinone (500 mg,
3.05 mmol) and DMAD (520 mg, 3.66 mmol) in anhyd benzene
(10 mL) at 80 °C was added Ph3P (400 mg, 1.52 mmol) and the mix-
ture was refluxed for 5 h. Chromatography on silica gel using 80:20
hexanes/EtOAc afforded an inseparable mixture of the spirolac-
tones 6a and 6b as a viscous yellow oil (242 mg, 26%).
IR (KBr): = 1782 (OC=O), 1729 (CO2Me), 1676 (C=O), 1656
cm 1 (C=C).
1H NMR: = 1.17 (s, 9 H), 1.25 (s, 9 H), 3.68 (s, 6 H), 4.31 (s, 6 H),
5.71 (d, 1H, J = 1.9 Hz), 6.03 (d, 1 H, J = 10.0 Hz), 6.12 (s, 1 H),
6.25 (d, 1 H, J = 10.2 Hz), 6.61 (d, 1 H, J = 10.1 Hz),7.19 7.23
(dd, 1 H, J = 10.1, 1.8 Hz).
13C NMR: = 27.9, 28.3, 34.7, 35.7, 51.8, 51.9, 60.0, 77.2 78.4,
119.2, 125.0, 125.6, 128.42, 132.9, 141.9, 147.5, 149.6, 160.6,
163.7, 165.9, 192.3, 192.4.
EIMS: m/z (%) = 306 (M+, 36), 291 (9), 277 (27), 274 (20), 262
(19), 259 (100), 247 (61), 231 (45), 203 (26), 175 (19), 163 (21),
147 (14), 135 (22), 115 (42), 91 (63), 79 (39), 77 (54), 65 (27), 59
(68).
7,9-Di-tert-butyl-3,6-dimethoxy-2,10-dioxo-1-oxaspiro[4.5]de-
ca-3,6,8-triene-4-carboxylic Acid Methyl Ester (3)
To a mixture of 4,6-di-tert-butyl-3-methoxy-1,2-benzoquinone
(100 mg, 0.4 mmol) and DMAD (68 mg, 0.48 mmol) in refluxing
anhyd benzene (5 mL) was added Ph3P (52 mg, 0.2 mmols) and the
reflux was continued for 4 h. After removal of the solvent the resi-
due was purified by chromatography on silica gel using 90:10 hex-
anes/EtOAc to afford 3 as a viscous yellow oil (107 mg, 70%).
Spiro[naphthylene-1(2H),3-methoxy-4-methoxycarbonylfuran-
2-one]-8-one (7a) and Spiro[naphthylene-1(2H),3-methoxy-4-
methoxycarbonylfuran-2-one]-2-one (7b)
IR (KBr): = 1793 (OC=O), 1729 (CO2Me), 1681 (C=O), 1655
cm 1 (C=C).
To a refluxing mixture of 1,2-naphthoquinone (125 mg, 0.79 mmol)
and DMAD (135 mg, 0.95 mmol) in anhyd benzene (5 mL)
was added Ph3P (104 mg, 0.39 mmol) and heating was continued at
Synthesis 2000, No. 12, 1713–1718 ISSN 0039-7881 © Thieme Stuttgart · New York

1716
V. Nair et al.
Table 2 Addition of Dimethyl Acetylenedicarboxylate to 1,4-Quinones
PAPER
a
Product(s)
Quinone
O
Entry
Conditions
Yield(%)
O
O
1
Benzene
RT, 12 h
+
89
CO2Me
CO2Me
O
O
O
O
O
O
OMe
12b
OMe
(4: 1)
12a
O
Benzene
RT, 12 h
2
73 (91)b
CO2Me
OMe
O
O
O
O
13
O
t
Bu
t
Bu
Benzene
RT, 24 h
3
t
Bu
26 (39)
CO2Me
OMe
t
Bu
O
O
O
14
O
O
O
26 (66)
Benzene
80 °C, 24 h
4
CO2Me
OMe
O
O
15
a Isolated yield.
b Yield based on recovered quinone in parenthesis.
80 oC for 4 h. The solvent was evaporated and the residue was sep-
arated by radial chromatography on a Chromatotron® using 90:10
hexanes/EtOAc afforded 7a as a yellow solid (54 mg, 23%). Further
elution with the same solvent mixture afforded the spirolactone 7b
also as a yellow solid (55 mg, 23%).
13C NMR: = 52.0, 60.1, 79.0, 126.6, 127.0, 128.4, 129.0, 131.8,
135.4, 136.1, 145.7, 149.1, 160.5, 166.2, 190.7.
EIMS: m/z (%) = 285 (M+ Me, 18), 284 (100), 254 (14), 253 (61),
226 (30), 223 (26), 195 (24), 166 (11), 139 (46), 138 (32), 126 (26),
86 (15), 63 (8), 59 (9).
7a
IR (KBr): = 1795 (OC=O), 1719 (CO2Me), 1695 (C=O), 1663
7,9-Bis(diphenylmethyl)-3,6-dimethoxy-2,10-dioxo-1-oxa-
spiro[4.5]deca-3,6,8-triene-4-Carboxylic Acid Methyl Ester (8)
To a mixture of 3-methoxy-4,6-bis(diphenylmethyl)-1,2-benzo-
quinone (250 mg, 0.53 mmol) and DMAD (108 mg, 0.76 mmol) in
refluxing anhyd benzene was added Ph3P (70 mg, 0.26 mmol) and
the mixture was stirred for 1.5 h. Chromatography of the residue on
silica gel using 80:20 hexanes/EtOAc afforded 8 as yellow crystals
(125 mg, 46%).
cm 1 (C=C).
1H NMR: = 3.55 (s, 3 H, CO2CH3), 4.30 (s, 3 H, =COCH3), 5.90
(d, 1 H, J = 10.6 Hz, =CH), 6.91 (d, 1 H, J = 10.6 Hz, =CH), 7.25
7.75 (m, 3 H, ArH), 8.00 (dd, 1 H, J = 7.9, 1.3 Hz, ArH).
13C NMR: = 52.0. 60.1, 79.0, 121.7, 126.9, 127.6, 128.4, 128.5,
129.0, 131.7, 135.4, 136.1, 149.3, 160.8, 166.0, 190.7.
EIMS: m/z (%) = 285 (M+ Me, 0.5), 284 (2.5), 256 (M+ CO2,
IR (KBr): = 1782 (OC=O), 1732 (CO2Me), 1685 (C=O), 1655
cm 1 (C=C).
75), 241 (M+ CO2Me, 100).
7b
1H NMR: = 3.45 (s, 3 H, OCH3), 3.59, (s, 3 H, CO2CH3), 4.28 (s,
3 H, =COCH3), 5.36 (s, 1 H, CHPh2), 5.59 (s, 1 H, CHPh2), 6.52 (s,
1 H, =CH), 6.90 7.02 (m, 8 H, ArH), 7.14 7.24 (m, 12 H, ArH).
13C NMR: = 48.0, 49.0, 51.9, 52.4, 60.4, 63.2, 81.5, 120.2, 126.2,
126.5, 126.5, 126.9, 126.9, 128.2, 128.4, 128.5, 128.7, 128.9, 136.2,
141.2, 141.3, 144.4, 150.3, 152.0, 160.2, 166.1, 190.2.
IR (KBr): = 1779 (OC=O), 1709 (CO2Me), 1681 (C=O), 1658
cm 1 (C=C).
1H NMR: = 3.52 (s, 3 H, CO2CH3), 4.31 (s, 3 H, =COCH3), 6.41
(d, 1 H, J = 11 Hz, C=CH), 7.44 (m, 4 H, ArH), 7.53 (d, 1 H, J = 11
Hz, CH=C).
Synthesis 2000, No. 12, 1713–1718 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Triphenylphosphane-Mediated Addition of Dimethyl Acetylenedicarboxylate
1717
Spiro[acenaphthylene-1(2H),3-methoxy-4-methoxycarbonylfu-
ran-2-one]-2-one(9)
1H NMR: = 1.94 (d, 3 H, J = 1.43 Hz, CH3), 3.72 (s, 3 H,
CO2CH3), 4.30 (s, 3 H, =COCH3) 6.25 (t, 1 H, J = 2.9 Hz, =CH),
6.38 (d, 1 H, J = 9.9 Hz, CH), 6.46 (dd, 1 H, J = 9.9, 2.8 Hz, =CH),
13C NMR: = 15.8. 52.3, 60.2, 77.8, 121.1, 131.6, 137.1, 138.9,
142.0, 149.5, 160.5, 165.0, 184.9.
To a mixture of acenaphthenequinone (364 mg, 2.0 mmol) and
DMAD (625 mg, 4.4 mmol) in anhyd benzene (15 mL) at 80 °C was
added Ph3P (262 mg, 1.0 mmol) and the mixture was stirred for 1 h.
The residue on chromatographic separation on silica gel using 75:25
hexanes/EtOAc gave the spirolactone 9 as a white solid (353 mg,
55%); mp 121 122 °C (benzene/hexanes).
Anal. calcd for C13H12O6: C, 59.09; H; 4.58. Found C, 59.23; H,
4.55.
IR (KBr): = 1780 (OC=O), 1735 (CO2Me), 1705 (C=O), 1653
cm 1 (C=C).
1H NMR: = 3.37 (s, 3 H, CO2CH3), 4.41 (s, 3 H, =COCH3), 7.50
(d, 1 H, J = 6.88 Hz, ArH), 7.64 7.70 (m, 1 H, ArH), 7.77 7.82 (m,
1 H, ArH), 8.01 (d, 1 H, J = 8.3 Hz, ArH), 8.08 (d, 1 H, J = 6.9 Hz,
ArH), 8.20 (d, 1 H, J = 8.1 Hz, ArH).
13C NMR: = 52.0, 60.3, 85.2, 121.2, 123.1, 127.2, 128.5, 130.8,
132.3, 143.2, 149.3, 160.8, 165.8, 195.0.
EIMS: m/z (%) = 325 (M + + 1, 1.7), 324 (M+, 8.9), 309 (1), 280
(11), 265 (100), 237 (31), 194 (15), 179 (15), 150 (30), 138 (23),
126 (21), 75 (13), 59 (16), 44 (22).
3-Methoxy-6,9-dimethyl-2,8-dioxo-1-oxaspiro[4.5]deca-3,6,9-
triene-4-carboxylic Acid Methyl Ester (13)
To
a mixture of 2,5-dimethyl-1,4-benzoquinone (500 mg,
3.67 mmol) and DMAD (650 mg, 4.57 mmol) in anhyd benzene
(10 mL) at r.t. under argon was added Ph3P (482 mg, 1.84 mmol)
and the mixture was stirred for 24 h. After the solvent was removed,
the residue was chromatographed on silica gel. Elution with 95:5
hexanes/EtOAc removed the unreacted quinone (99 mg). Further
elution gave 13 as colourless needles (752 mg, 73%). The yield
based on the reacted quinone is 91%; mp 107 109 °C (CH2Cl2/hex-
anes).
1
IR (KBr): = 1778, 1764 (OC=O), 1719 ((CO2Me), 1685 cm
(C=O).
3-Methoxy-2,8-dioxo-1-oxaspiro[4.5]deca-3,6,9-triene-4-car-
boxylic Acid Methyl Ester (11)
1H NMR: = 1.82 (d, 3 H, J = 1.4 Hz, CH3), 1.93 (d, 3 H, J = 1.5
Hz, CH3), 3.71 (s, 3 H, CO2CH3), 4.29 (s, 3 H, =COCH3) 6.22 6.27
(dd, 2 H, J = 11.8, 1.4 Hz, =CH).
13C NMR: = 15.3, 16.7, 52.4, 60.2, 79.6, 121.4, 129.8, 137.2,
138.5, 149.4, 150.5, 160.4, 165.4, 185.4.
EIMS: m/z (%) = 278 (M+, 12), 246 (25), 235 (37), 219 (32), 203
(41), 191 (61), 175 (30), 163 (17), 147 (22), 131 (31), 103 (39), 77
(67), 59 (100), 51 (42).
A mixture of 1,4-benzoquinone (500 mg, 4.63 mmol) DMAD
(790 mg, 5.56 mmol) in anhyd benzene (10 mL) was purged with
argon and stirred at r.t. To this Ph3P (606 mg, 2.31 mmols) was add-
ed and the mixture was stirred for 12 h. Removal of the solvent and
chromatography on silica gel using 80:20 hexanes/EtOAc afforded
11 as colorless prisms (1.022 g 88%); mp 120 122 °C (benzene/
hexanes).
IR (KBr): = 1774 (OC=O), 1727 (CO2Me), 1680 (C=O), 1647
cm 1 (C=C).
Anal. calcd for C14H14O6: C, 60.43; H, 5.07. Found C, 60.33; H, 5.1.
1H NMR: = 3.73 (s, 3 H, CO2CH3), 4.31 (s, 3 H, =COCH3), 6.37
6.54 (m, 4 H, CH=CH).
13C NMR: = 52.3. 60.3, 76.9, 120.6, 131.5, 142.2, 149.8, 160.3,
164.8, 184.1.
6,9-Di-tert-butyl-3-methoxy-2,8-dioxo-1-oxaspiro[4.5]deca-
3,6,9-triene-4-carboxylic Acid Methyl Ester (14)
A
mixture of 2,5-di-tert-butyl-1,4-benzoquinone (500 mg,
2.27 mmol) and DMAD (388 mg, 2.72 mmol) in anhyd benzene
(10 mL) under argon was treated with Ph3P (298 mg, 1.13 mmol) at
r.t. and the mixture was stirred for 24 h. The residue obtained after
the removal of the solvent was chromatographed on silica gel using
95:5 hexanes/EtOAc removed the unreacted quinone (251 mg) and
further elution with 90:10 hexanes/EtOAc yielded 14 as light
yellow crystals (214 mg, 26%); mp 121 123 °C (CH2Cl2/hexanes).
Anal. calcd for C12H10O6: C, 57.61; H, 4.03. Found C: 57.53; H,
4.06.
3-Methoxy-7-methyl-2,8-dioxo-1-oxaspiro[4.5]deca-3,6,9-
triene-4-carboxylic Acid Methyl Ester (12a) and 3-Methoxy-6-
methyl-2,8-dioxo-1-oxa-spiro[4.5]deca-3,6,9-triene-4-carboxyl-
ic Acid Methyl Ester (12b)
IR (KBr): = 1796 (OC=O), 1723 (CO2Me) 1667 cm 1 (C=O).
To a mixture of 2-methyl-1,4-benzoquinone (500 mg, 4.1 mmol)
and DMAD (700 mg, 4.9 mmol) in anhyd benzene (10 mL) was
added Ph3P (540 mg, 2.05 mmol) under argon at r.t. during 12 h.
The solvent was removed and the residue on radial chromatography
with 90:10 hexanes/EtOAc afforded 12a as white needles (198 mg,
18%); mp 116 118 °C (benzene/ hexanes). Further elution gave
12b as a white solid (775 mg, 71%); mp 112 113 °C (benzene/hex-
anes).
1H NMR: = 1.17 (s, 9 H, t-C4H9),1.21 (s, 9 H, t-C4H9), 3.66 (s, 3
H, CO2CH3), 4.25 (s, 3 H, =COCH3), 5.91 (s, 1 H, =CH), 6.34 (s, 1
H, =CH).
13C NMR: = 28.7, 30.8, 34.3, 37.2, 52.1, 60.0, 82.2, 123.4,
131.3,140.1, 146.9, 149.1, 157.2, 160.6, 165.8, 186.0.
Anal. calcd for C20H26O6: C, 66.28; H, 7.25. Found C, 66.37; H,
7.48.
12a
Spiro[naphthylene-1(2H),3-methoxy-4-methoxycarbonylfuran-
2-one]4-one (15)
IR (KBr): = 1782 (OC=O, sharp), 1769 (OC=O, weak), 1719
(CO2Me), 1677 cm 1 (C=O).
Ph3P (420 mg, 1.60 mmol) was added to a refluxing mixture of
1,4-naphthoquinone (500 mg, 3.16 mmol) and DMAD (542 mg,
3.81 mmol) in anhyd benzene (10 mL) and the heating was contin-
ued for 4 h. The solvent was removed and the residue on chromato-
graphic separatoin on silica gel using 95:5 hexanes/EtOAc removed
the unreacted quinone (300 mg) and elution with 80:20 hexanes/
EtOAc afforded the product 15 as light yellow crystals (250 mg,
26%); mp 180 182 °C. The yield based on the reacted starting
material was 66%.
1H NMR: = 1.82 (d, 3 H, J = 1.39, CH3), 3.71 (s, 3 H, CO2CH3),
4.30 (s, 3H, =COCH3), 6.28 (t, 1 H, J = 1.4, =CH), 6.36 (dd, 1 H,
J = 9.9, 1.7 Hz, =CH), 6.45 (d, 1 H, J = 9.9, =CH).
13C NMR: = 17.1. 52.5, 60.4, 78.9, 121.2, 130.0, 131.3, 142.4,
149.8, 150.9, 160.4, 165.2, 184.8.
Anal. calcd for C13H12O6: C, 59.09; H, 4.58. Found C, 59.53; H,
4.37.
12b
IR (KBr): = 1768 (OC=O), 1707 (CO2Me), 1676 cm 1 (C=O).
Synthesis 2000, No. 12, 1713–1718 ISSN 0039-7881 © Thieme Stuttgart · New York

1718
V. Nair et al.
PAPER
IR (KBr): = 1761 (OC=O), 1706 (CO2Me), 1681 (C=O), 1643
cm 1 (C=C).
(6) Brunn, E.; Huisgen, R. Angew. Chem. Int. Ed. Engl. 1969, 8,
513.
(7) Johnson, A. W.; Tebby, J. C. J. Chem. Soc. 1961, 2126.
(8) Tebby, J. C.; Wilson, I. F.; Griffiths, D. V. J. Chem. Soc.,
Perkin Trans. 1 1979, 2133.
(9) Shaw, M. A.; Tebby, J. C.; Ward, R. S. Williams, D. H. J.
Chem. Soc. (C) 1970, 504.
(10) Shaw, M. A.;Tebby, J. C.; Ward, R. S.; Williams, D. H. J.
Chem. Soc. (C) 1968, 1609.
(11) Shaw, M. A.; Tebby, J. C.; Ward, R. S.; Williams, D. H. J.
Chem. Soc.(C). 1968, 2795.
1H NMR: = 3.54 (s, 3 H, CO2CH3), 6.60 (s, 2 H, =CH), 4.38 (s, 3
H, =COCH3), 7.21 (d, 1 H, J = 7.6 Hz, ArH),7.50 7.62 (m. 2 H,
ArH), 8.16 (dd, 1 H, J = 7.5, 1.0 Hz, ArH).
13C NMR: = 52.2, 60.5, 78.4, 123.4, 127.1, 127.3, 129.7, 131.3,
131.8, 133.2, 136.8, 142.6, 149.3, 160.3, 165.7, 183.5.
Anal. calcd for C16H12O6: C, 64.00; H, 4.03. Found C, 63.87; H,
3.99.
(12) Butterfield, P. J.; Tebby, J. C.; Griffiths, D. V. J. Chem. Soc.,
Perkin Trans. 1 1979, 1189.
(13) Tebby, J. C.; Wilson, I. F.; Griffiths, D. V. J. Chem. Soc.,
Perkin Trans. 1 1979, 2133.
(14) Winterfeldt, E.; Dillinger, H. J. Chem. Ber. 1966, 99, 1558.
(15) Nozaki, K.; Sato, N.; Ikeda, K.; Takaya, H. J. Org. Chem.
1996, 61, 4516.
Acknowledgement
JSN and AUV thank CSIR, New Delhi, for research fellowships.
Thanks are also due to Dr. Sasi Kumar, Dr. Jessy Mathew, Dr. Jaya
Prabhakaran, Dr. P. Shanmugam, and Ms. Soumini Mathew for
high resolution NMR spectra and elemental analyses.
(16) For a review, see: Nair, V.; Kumar, S.; Synlett 1996, 1143.
(17) Nair, V.; Anilkumar, G.; Radhakrishnan, K. V.; Sheela K. C.;
Rath, N. P. Tetrahedron 1997, 53, 17361.
References
(18) Nair V.; Radhakrishnan, K. V.; Nair, A. G.; Bhadbhade, M.
M. Tetrahedron Lett. 1996, 37, 5623.
(19) Nair,V.; Nair J. S.; Vinod, A. U.; Rath, N. P. J. Chem. Soc.,
Perkin Trans. 1 1997, 3129.
(20) (a) Roush, W. R.; Reily, M. L.; Koyama,K.; Brown, B. B. J.
Org. Chem. 1997, 62, 8708.
(1) (a) Bohlmann, R. In Comprehensive Organic Synthesis; Trost,
B. M.; Fleming, I., Eds.; Pergamon: London, 1991, Vol. 6.,
Chap. 1.7, p 203.
(b) Sustmann, R.In Comprehensive Organic Synthesis; Trost,
B. M.; Fleming, I., Eds.; Pergamon: London, 1991, Vol.6.
Chap. 2.1, p 301.
(b) Roush, W. R.; Sciotti, R. J. Am. Chem. Soc. 1998, 120,
7411.
(c) Organic Phosphorous Compounds; Kosolapoff, G. M.;
Maier, L., Eds.; Wiley: New York, 1973.
(c) Roush, W. R.; Sciotti, R. J. Org. Chem. 1998, 63, 5473.
(2) Johnson, A. W. Ylides and Imines of Phosphorus, Chap. 1, p
1, Wiley: New York, 1993.
(3) Trost, B. M.; Kasmaier, U. J. Org. Chem. 1987, 52, 3927.
(4) Trost, B. M.; Kasmaier, U. J. Am. Chem. Soc. 1992, 114,
7933.
Article Identifier:
1437-210X,E;2000,0,12,1713,1718,ftx,en;Z04900SS.pdf
(5) Zhang, C.; Lu, X. J. Org. Chem. 1995, 60, 2906.
Synthesis 2000, No. 12, 1713–1718 ISSN 0039-7881 © Thieme Stuttgart · New York