The reaction of (chlorocarbonyl)phenyl ketene with enaminones: A novel synthesis of some 5-Acyl-4-hydroxy-2- (1H)-pyridinones and 7-hydroxy-5-oxo-1,4- diazepin derivative

Article abstract of DOI:10.1002/jhet.14

A series of substituted 5-acyl-4-hydroxy-2-(1H)-pyridinone derivatives has been prepared in a one-step procedure from condensation of (chlorocarbonyl) phenyl ketene with some enaminones which were prepared from 1,3-diketones, such as 2,4-pentanedione, 1-p

Full text of DOI:10.1002/jhet.14

96
The Reaction of (Chlorocarbonyl)phenyl Ketene with
Enaminones: A Novel Synthesis of Some 5-Acyl-4-hydroxy-2-
(1H)-pyridinones and 7-Hydroxy-5-oxo-1,4-diazepin Derivative
Vol 46
Mehdi Abaszadeh, Hassan Sheibani,* and Kazem Saidi
Department of Chemistry, Shahid Bahonar University of Kerman, Kerman 76169, Iran
*E-mail: hsheibani@mail.uk.ac.ir
Received January 23, 2008
DOI 10.1002/jhet.14
Published online 5 February 2009 in Wiley InterScience (www.interscience.wiley.com).
A series of substituted 5-acyl-4-hydroxy-2-(1H)-pyridinone derivatives has been prepared in a one-
step procedure from condensation of (chlorocarbonyl)phenyl ketene with some enaminones which were
prepared from 1,3-diketones, such as 2,4-pentanedione, 1-phenyl-1,3-butanedione, and ethyl acetoacetate
in boiling toluene as a solvent. A mechanism is presented to account for the formation of the products.
The overall sequence provides a simple and efficient route to prepare 3,4,5,6-tetrasubstituted 2-(1H)-pyr-
idinone in good to excellent yields and in a short experimental time.
J. Heterocyclic Chem., 46, 96 (2009).
INTRODUCTION
[13,14], as well as cycloaddition [15] and cyclization
procedures [16].
Heterocycles having a 2-pyridinone framework are
an extensively studied class of compounds, owing
partly to their diverse biological activities such as anti-
bacterial [1] and antifungal [2] agents for free radical
scavengers [3]. Ring fused 2-pyridinones have also
attracted attention as lead compounds for the prepara-
tion of selective anticancer drugs [4,5], antiviral agents
[6], angiotensin-converting enzyme (ACE) inhibitors
[7], as well as inhibitors of A b-peptide aggregation
[8], which is believed to play an important role in amy-
loid formation in Alzheimer’s disease. In addition,
dihydro and tetrahydro derivatives of 2-pyridinones
have been applied as scaffolds for the construction of
constrained amino acids [9,10]. With all these diverse
properties in mind, medicinal chemists often incorpo-
rate these motifs in the design of novel biologically
active molecules.
Fewer general methods exist for the preparation of 2-
pyridinones substituted with aryl substituents and elec-
tron withdrawing groups such as CN, COR, COOR, and
CONR2 at positions C3 and C5. Reported of 5-acyl-3-
aryl-2-pyridinones usually include (Scheme 1) (i) reac-
tion of 1,3-diketones with 2-arylacetamides (yields of I
ca. 40%) [17]; (ii) Michael addition of arylacetamides
or arylacetonitrile to 1,3-diaryl-2-propyne-1-ones afford-
ing products with limited diversity (3,4,6-triaryl
substituted pyridinones in yields about 20%) [18]; (iii)
Michael addition of 2-arylacetamides to 1,3-diaryl-2-
propene-1-ones, is followed by cyclization subsequent
oxidative aromatization of the intermediate dihydropyri-
dinones with selenium at the high-temperature to yield
76–94% of the product I [19]; (iv) and finally synthesis
via one-step [1 þ 2 þ 3] reactions of an aldehyde, a-
benzotriazolyl ketone and arylacetamides [20].
Ever since the first synthesis of 2-pyridinones was
reported via a ferricyanide-mediated oxidation of pyri-
dinium salts [11], many different methods for construct-
ing these heterocycles in solution have appeared in the
literature. Some of these reports include intramolecular
Dieckmann like condensations [12], Michael additions
RESULTS AND DISCUSSION
In continuing our interest in the synthesis of heterocy-
clic compounds by using chlorocarbonyl ketenes and
C
V
2009 HeteroCorporation

January 2009
Reaction of (Chlorocarbonyl)phenyl Ketene with Enaminones
97
Scheme 1
Scheme 3
the synthesis of 5-acyl-4-hydroxy-2-(1H)-pyridinone
derivatives from the reaction of enaminones with dialkyl
malonates under harsh experimental conditions [low
yields (42–68%) and also long reaction times].
The chemical importance and diversity of pyridinones
have made these compounds important synthetic goals
and have stimulated new methods and reagents for the
preparation of these heterocyclic compounds. In an
effort to extend the scope and generality of the conden-
sation reaction (Scheme 1) (chlorocarbonyl)phenyl ke-
tene 2 was treated with enaminones 1. The only product
formed under these conditions was 5-acyl-4-hydroxy-3-
phenyl-2-(1H)-pyridinones 3 in excellent yields in a
short experimental time.
In this case, it was also found that the reaction of
with (chlorocar-
1,3-binucleophiles such as 1,3-diketones [21], amides
[22,23] and thioamides [24]; in this article we wish to
report a one-pot synthesis of 5-acyl-4-hydroxy-2-(1H)-
pyridinone derivatives which were prepared in a one-
step procedure from readily available (chlorocarbonyl)-
phenyl ketene and enaminones as 1,3-binucleophile.
This method provides an easy route to prepare 2(1H)-
pyridinones in good to excellent yields and short experi-
mental time (Scheme 2).
ethyl-3-(butylamino)-2-butenoate
4
chloro-carbonyl)phenyl ketene 2 produce the corre-
sponding pyridinone 5 (Scheme 3). It is pertinent to
note that with the same experimental condition as the
previous reaction different tautomer was formed.
The cycloaddition reaction of 4-[(2-aminoethyl)
amino]-3-penten-2-one 6 with (chlorocarbonyl)phenyl
ketene 2 resulted in the formation of ethyl (E)-3-(7-
hydroxy-5-oxo-6-phenyl-2,3,4,5-tetrahydro-1H-1,4-diaze-
pin-1-yl)-2-butanoate 7 as the only product (Scheme 4).
On the basis of this report, (chlorocarbonyl)aryl
ketenes undergo a degenerate 1,3-shift of chlorine, as
determined by 13C NMR spectroscopy [28]. On the basis
of our results, which was aforementioned, a plausible
mechanism has been proposed for the reactions of
(chlorocarbonyl)phenyl ketene with enaminones to yield
2-(1H)-pyridinone derivatives, as shown in Scheme 5.
Initially, the NH group of enaminone as a good nucleo-
phile will attack the acyl chloride of ketene, followed
by ring closure of intermediate 2 to produce the
product.
Enaminones are versatile synthetic intermediatates
that combine the ambident nucleophilicity of enamines
with the ambident electrophilicity of enones [25]. There
are many reports in the literature on the functionaliza-
tion of enaminone by the introduction of different
substituents on the nitrogen, the a-carbon and the b-car-
bonylic carbon atoms. These derivatives have been
extensively used for the preparation of a variety of het-
erocyclic systems including some natural products and
analogues [26]. Thomas Kappe et al. [27], have reported
Scheme 2
The structure of 3a-g and compounds 5 and 7 were
1
determined on the basis of their mass spectra, H and
Scheme 4
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

98
M. Abaszadeh, H. Sheibani, and K. Saidi
Vol 46
Scheme 5
mixture was cooled and the solid product was collected and
recrystallized from dry ethyl acetate hexane.
5-Acetyl-4-hydroxy-6-methyl-1,3-diphenyl-2(1H)-pyridi-
none (3a). A 0.60 g red crystals, yield 95%, mp 224–226ꢀC
(dec.); IR (KBr): 3200–2500 (broad peak, OH), 1716, 1641
(C¼¼O), 1567 (C¼¼C) cmꢁ1
;
1H NMR (DMSO): d 10.7 (1H,
broad, OH), 7.62–7.10 (10H, m, arom), 2.33(3H, s, CH3),
2.17(3H, s, CH3); 13C NMR (DMSO): d 200.36, 163.90, and
163.13, 161.61, 131. 88, 131.15, 130.81, 129.65, 128.05,
128.00, 127.44, 123.28, 115.38, 103.79, 32.20, and 19.26; MS,
m/z (relative intensity %): 319(Mþ, 4), 291(5), 244(18),
216(32), 198(17), 160(17), 145(8), 127(15), 118(30), 93(38),
77(28), 65(20), 43(100). Anal. Calcd. For C20H17NO3: C,
75.22; H, 5.37; N, 4.39%. Found: C, 74.89; H, 5.46; N,
4.16%.
1
13C NMR and IR spectroscopic data. The H NMR and
13C NMR spectra of 4-hydroxy-3,6-disubstituted-2(1H)-
pyridinone derivatives 3a-d exhibited only one
tautomer.
5-Acetyl-4-hydroxy-1-(4-methoxy-phenyl)-6-methyl-3-phe-
nyl-2(1H)-pyridinone (3b). A 0.61 g red crystals, yield 88%,
mp 230–232ꢀC (dec.); IR (KBr): 3200–2550 (broad peak,
OH), 1741, 1666(C¼¼O), 1517 (C¼¼C) cmꢁ1
;
1H NMR
(DMSO): d 10.58(1H, broad, OH), 7.38–7.00 (9H, m, arom),
3.74 (3H, s, OCH3), 2.49(3H, s, CH3), 2.32(3H, s, CH3);
13CNMR (DMSO): d 200.37, 163.89 and 163.15, 161.63,
158.75, 131.10, 130.65, 128.06, 128.51, 127.46, 124.11,
115.41, 114.79, 103.40, 55.45, 32.21, and 19.27; MS, m/z (rel-
ative intensity %): 349 (Mþ, 2), 244 (25), 216(70), 198(18),
190 (16), 127(20), 123 (100), 118(35), 85(48), 80(35), 63(17),
43(90). Anal. Calcd. For C21H19NO4: C, 72.19; H, 5.48; N,
4.01%. Found: C, 71.98; H, 5.50; N; 3.70%.
1
The H NMR spectrum of 3a showed four kinds of
proton signals. One signal quite downfield (d 10.70
ppm) which is the proton of enol OH and a multiplet
(d ¼ 7.62–7.10) for the aromatic protons (10 H) along
with two signals at (d ¼ 2.33 and 2.17 ppm) which
were identified as an acyl group in position 5 and the
other methyl group in position 6. The 13C NMR and
mass spectra are also in accordance with the proposed
structure.
5-Acetyl-1-(4-dimethylaminophenyl)-4-hydroxy-6-methyl-
3-phenyl-2(1H)-pyridinone (3c). A 0.62 g yellow crystals,
yield 86%, mp 235–238ꢀC (dec.); IR (KBr): 3200–2550 (broad
We have shown that the condensation reaction of
(chlorocarbonyl)phenyl ketene with enaminones occurs
efficiently in boiling toluene as a solvent, providing a
convenient and rapid synthesis of 4-hydroxy-3,4,6-tri
substituted-2(1H)-pyridinone in high yield, by a simple
procedure and short experimental time. Furthermore, the
products are solid and precipitate out from the reaction
mixture and their purifications are simple.
peak, OH), 1741, 1666 (C¼¼O), 1535 (C¼¼C) cmꢁ1
;
1H NMR
(DMSO): d 10.37 (1H, broad, OH), 7.78–7.25 (9H, m, arom),
3.03 (6H, s, 2CH3), 2.05 (3H, s, CH3), 1.93 (3H, s, CH3), 2.05
(3H, s, CH3), 1.93 (3H, s, CH3); 13CNMR (DMSO): d 200.10,
168.74, and 162.25, 159.67, 146.83, 132.81, 130.84, 129.34,
127.78, 121.34, 110.17, 100.17, 42.67, 32.66, 19.38; MS, m/z
(relative intensity %): 362 (Mþ, 40), 347(5), 334(10), 294(15),
203(65), 187 (42), 178(28), 161(38), 135(95), 121(38),
105(25), 91(100), 77(48), 65(68), 50(27). Anal. Calcd. For
C22H22N2O3: C, 72.91; H, 6.12; N, 7.73%. Found: C, 72.60;
H, 6.20; N, 7.53%.
EXPERIMENTAL
5-Acetyl-4-hydroxy-6-methyl-3-phenyl-1-p-toly1-2(1H)-
pyridinone (3d). A 0.61 g red crystals, yield 92%, mp 228–
232ꢀC (dec.); IR (KBr): 3200–2550 (broad peak, OH), 1716,
(Chlorocarbonyl)phenyl ketene was prepared according to
the literature procedure [29]. The enaminones are known and
were prepared according to the general procedure reported in
the literature [30].
Toluene, hexane, diethyl ether, and THF were dried over so-
dium and distilled prior to use. Melting points were measured
on a calibrated Gallenkamp melting point apparatus. IR spectra
were measured with a Mattson 1000 FT-IR spectrometer. 1H
and 13C NMR spectra were measured with a BRUKER DRX-
300 AVANCE spectrometer at 300.13 and 75.47 MHz, respec-
tively. Mass spectra were recorded on a MS-QP2000A Shi-
madzu mass spectrometer operating at an ionization potential
of 70 eV.
1
1641 (C¼¼O), 1567 (C¼¼C) cmꢁ1; H NMR (DMSO): d 10.63
(1H, broad, OH), 7.49–6.88 (9H, m, arom), 2.32 (3H, s, CH3),
2.28 (3H, s, CH3), 2.14 (3H, s, CH3); 13C NMR (DMSO): d
200.37, 163.97 and 163.16, 161.60, 137.56, 130.81, 130.01,
129.05, 128.87, 128.18, 128.04, 123.16, 115.36, 103.38, 32.21,
20.52, and 19.30; MS, m/z (relative intensity %): 333(Mþ, 5),
244(20), 216(25), 178(20), 149(18), 135(50), 121(26),
105(100), 91(82), 77(43), 58(70), 51(27). Anal. Calcd. For
C21H19NO3: C, 75.66; H, 5.74; N, 4.20%. Found: C, 75.30; H,
5.69; N; 3.85%.
5-Benzoyl-4-hydroxy-1-isobutyl-6-methyl-3-phenyl-2(1H)-
pyridinone (3e). A 0.65 g purple crystals, yield 90%, mp
230–232ꢀC (dec.); IR (KBr): 3200–2550 (broad peak, OH),
General procedure (3a-d). To a stirred solution of corre-
sponding enaminone (2 mmol) in 20 mL dry boiling toluene, a
mixture of 0.36 g (chlorocarbonyl)phenyl ketene (2 mmol) in
5 mL dry THF was added dropwise over 2 min. The product
was formed immediately as a color precipitate. The reaction
1
1716, 1641 (C¼¼O), 1535 (C¼¼C) cmꢁ1; H NMR (DMSO): d
10.80 (1H, broad, OH), 7.58–7.27 (10H, m, arom), 3.51 (2H,
3
d, J ¼ 7.00 Hz, CH2), 2.25 (3H, s, CH3), 1.88 (1H, m, CH),
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

January 2009
Reaction of (Chlorocarbonyl)phenyl Ketene with Enaminones
99
3
3
0.91 (3H, d, J ¼ 6.00 Hz, CH3), 0.76 (3H, d, J ¼ 6.00 Hz,
CH3); 13CNMR (DMSO): d 200.28, 163.21, and 162.50,
159.30, 131.54, 131.06, 130.79, 129.03, 128.90, 128.32,
128.10, 127.26, 116.23, 104.57, 45.59, 32.21, 26.30, 19.80,
and 19.79; MS, m/z (relative intensity %): 361 (Mþ, 7),
346(4), 306(38), 278 (30), 200(20), 189(15), 129(13), 118(18),
105(100), 89(22), 77(90), 63(14), 51(20). Anal. Calcd. For
C23H23NO3: C, 76.43; H, 6.41; N, 3.88%. Found: C, 76.08; H,
6.10; N, 3.56%.
13.66; MS, m/z (relative intensity%): 330 (Mþ1, 9), 329(Mþ,
35), 314(82), 283(80), 288(35), 227(92), 213(28), 199(25),
128(23), 91(100), 77(15), 67(24). Anal. Calcd. For
C17H20N2O4: C, 64.54; H, 6.37; N, 8.85%. Found: C, 64.23;
H, 6.25; N, 8.55%.
Acknowledgments. The authors express appreciation to the Sha-
hid Bahonar University of Kerman Faculty Research Committee
Fund for its support of this investigation.
5-Benzoyl-1-butyl-4-hydroxy-6-methyl-3-phenyl-2(1H)-pyri-
dinone (3f). A 0.65 g purple crystals, yield 91%, mp 220–
222ꢀC (dec.); IR (KBr): 3200–2550 (broad peak, OH), 1716,
1641(C¼¼O), 1515(C¼¼C) cmꢁ1
;
1H NMR (DMSO): d 10.50
REFERENCES AND NOTES
3
(1H, broad, OH), 7.54–7.26 (10H, m, arom), 2.71 (2H, t, J ¼
5.10 Hz, CH2), 2.27 (3H, s, CH3), 1.52 (2H, m, CH2), 1.30
(2H, m, CH2), 0.83 (3H, t, 3J ¼ 5.00 Hz, CH3); 13CNMR
(DMSO): d 200.95, 164.88, and 162.03, 158.07, 132.36,
131.94, 130.84, 130.69, 128.78, 128.16, 127.76, 126.76,
117.83, 103.16, 40.33, 32.27, 28.97, 19.14, and 13.45; MS, m/
z (relative intensity %): 361 (Mþ, 4), 346(5), 306(60), 278
(35), 200(18), 189(15), 147(10), 129(10), 118(18), 105(100),
89(20), 77(84), 63(10), 51(20), 43(37), 41(10). Anal. Calcd.
For C23H23NO3: C, 76.43; H, 6.41; N, 3.88%. Found: C,
76.13; H, 6.30; N, 3.58%.
[1] Dolle, R. E.; Nicolaou, K. C. J Am Chem Soc 1985, 107, 1695.
[2] Cox, R. J.; O’Hagan, D. J Chem Soc Perkin Trans 1991, 1, 2537.
[3] Teshima, Y.; Shin-ya, K.; Shimazu, A.; Furihata, K.; Chul,
H. S.; Hayakawa, Y.; Nagai, K.; Seto, H. J Antibiot 1991, 44, 685.
[4] Wall, M. E.; Wani, M. C.; Cook, C. E.; Palmer, K. H.;
McPhail, A. T.; Sim, G. A. J Am Chem Soc 1966, 88, 3888.
[5] Comins, D. L.; Nolan, J. M. Org Lett 2001, 3, 4255.
[6] Josien, H.; Curran, D. P. Tetrahedron 1997, 53, 8881.
[7] Mynderse, J. S.; Samlaska, S. K.; Fukuda, D. S.; Du Bus,
R. H.; Baker, P. J. J Antibiot 1985, 38, 1003.
[8] Kuner, P.; Bohrmann, B.; Tjernberg, L. O.; Naslund, J.;
Huber, G.; Celenk, S.; Gruninger-Leitch, F.; Richards, J. G.; Jakob-
Roetne, R.; Kemp, J. A.; Nordstedt, C. J Biol Chem 2000, 275, 1673.
[9] Creswell, M. W.; Bolton, G. L.; Hodges, J. C.; Meppen, M.
Tetrahedron 1998, 54, 3983.
5-Acetyl-4-hydroxy-6-methyl-3-phenyl-2(1H)-pyridinone (3g). A
0.46 g orange crystals, yield 96%, mp 258–260ꢀC (dec.); IR
(KBr): 3100–2550 (broad peak, OH), 1741, 1666 (C¼¼O), 1527
(C¼¼C)cmꢁ1
;
1H NMR (DMSO): d 12.90(1H, s, OH), 11.92
(1H, s, NH), 7.40–7.23(5H, m, arom), 2.58 (6H, s, 2CH3). 13C
NMR (DMSO): d 203.88, 165.08, and 162.57, 154.73, 133.59,
131.72, 128.28, 127.32, 109.69, 109.48, 33.57, and 21.57; MS,
m/z (relative intensity %): 243 (Mþ, 12), 216(19), 148(35),
118(25), 91(100), 77(35), 65(37), 51(23).
[10] Feng, Z.; Lubell, W. D. J Org Chem 2001, 66, 1181.
[11] Decker, H. Chem Ber 1892, 25, 443.
[12] Chung, K. H.; Cho, K. Y.; Asami, Y.; Takahashi, N.; Yosh-
ida, S. Heterocycles 1991, 32, 99.
[13] Aggarwal, V.; Singh, G.; Ila, H.; Junjappa, H. Synthesis 1982, 214.
[14] Datta, A.; Ila, H.; Junjappa, H. J Org Chem 1990, 55, 5589.
[15] Kappe, T.; Pocivalnik, D. Heterocycles 1983, 20, 1367.
[16] Zhang, S.; Liebeskind, L. S. J Org Chem 1999, 64, 4042.
[17] Hishmat, O. H.; Miky, J. A. A.; Saleh, N. M. Pharmazie
1989, 44, 823.
Ethyl 1-butyl-2-methyl-4,6-dioxo-5-phenyl-1,4,5,6-tetra-
hydro-3-pyridinecarboxylate (5). A 0.28 g yellow crystals,
yield 75%, mp 72–74ꢀC. IR (KBr): 1740, 1717 and 1650
(C¼¼O) 1530 (C¼¼C) cmꢁ1
;
1H NMR (DMSO): d 7.41–7.07
3
(5H, m, arom), 4.47 (1H, s, malonyl-H on C5), 4.14 (2H, t, J
¼ 7.00 Hz, OCH2), 4.06 (2H, t, 3J ¼ 6.00 Hz, NCH2), 2.52
(3H, s, CH3), 1.68 (2H, m, CH2), 1.42 (2H, quin, 3J ¼ 6.50
[18] Fouli, F. A.; Youssef, A. S. A.; Vernon, J. M. Synthesis
1988, 291.
3
3
[19] El-Rayyes, N. R.; Al-Hajjar, F. H. J Heterocycl Chem
1984, 21, 1473.
Hz, CH2), 1.21 (3H, t, J ¼ 5.00 Hz, CH3), 0.96 (3H, t, J ¼
5.00 Hz, CH3); 13C NMR (DMSO): d 170.46 and 164.87,
164.53, 162.59, 147.05, 129.83, 129.18, 128.69, 128.11,
62.04, 57.00, 45.79, 30.21, 22.68, 19.66, 14.04, and 13.66;
MS, m/z (relative intensity %): 330 (Mþ1, 9), 329 (Mþ, 35),
314(82), 283(80), 288(35), 227(92), 213(28), 199(25),
128(23), 91(100), 77(15), 67(24). Anal. Calcd. For
C19H23NO4: C, 69.28; H, 7.04; N, 4.25%. Found: C, 69.03;
H, 7.14; N, 4.07%.
[20] Katritzky, A. R.; Silina, A.; Tymoshenko, D. O.; Qiu, G.;
Nair, S. K.; Steel, P. J. Arkivoc 2001, 7, 138.
[21] Sheibani, H.; Islami, M. R.; Khabazzadeh, H.; Saidi, K.
Tetrahedron 2004, 60, 5932
[22] Sheibani, H.; Mosslemin, M. H.; Behzadi, S.; Islami, M. R.;
Saidi, K. Synthesis 2006, 3, 437.
[23] Sheibani, H.; Bernhardt, P. V.; Wentrup, C. J Org Chem
2005, 70, 5859.
Ethyl (E)-3-(7-hydroxy-5-oxo-6-phenyl-2,3,4,5-tetra hydro-
1H-1,4-diazepin-1-yl)-2-butanoate (7). A 0.27 g Yellow crys-
tals, yield 81%, mp 215–216ꢀC. IR (KBr): 3100–2550 (broad
[24] Sheibani, H.; Mosslemin, M. H.; Behzadi, S.; Islami, M. R.;
Foroughi, H.; Saidi, K. Arkivoc 2005, 15, 88.
[25] Greenhill, J. V. Chem Soc Rev 1977, 6, 277.
[26] Lue, P.; Greenhill, J. V. Adv Heterocycl Chem 1997, 67, 207.
[27] Kappe, T.; Ajili, S.; Stadlbauer, W. J Heterocycl Chem
1988, 25, 463.
peak, OH), 1721, 1655 (C¼¼O), 1530 (C¼¼C) cmꢁ1
;
1H NMR
(DMSO): d 10.45(1H, s, OH), 8.35 (1H, broad, NH), 7.38–
7.26 (5H, m, arom), 4.31 (2H, q, 3J ¼ 7.50 Hz, OCH2), 4.19
(1H, s, ¼¼CH), 3.65 (4H, m, CH2), 2.62 (3H, s, CH3), 1.29
[28] Finnerty, J.; Andraos, J.; Yamamoto, Y.; Wong, M. W.;
Wentrup, C. J Am Chem Soc 1998, 120, 1701.
3
(3H, t, J ¼ 7.50 Hz, CH3); 13CNMR (DMSO): d 170.46 and
164.87, 164.53, 162.59, 147.05, 129.83, 129.18, 128.69,
128.11, 62.04, 57.00, 45.79, 30.21, 22.68, 19.66, 14.04, and
[29] Stefani, A. H.; Costa, I. M.; Silva, D. O. Synthesis 2000, 1526.
[30] Nakanishi, S.; Butler, K. Org Prep Precd Int 1975, 7, 155.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet