PAPER
One-Pot Synthesis of Diketones and Keto Esters
2727
Anal. Calcd for C12H12O: C, 83.69; H, 7.02. Found: C, 83.77; H,
6.98.
Table 3 One-Pot Synthesis of Cyclopentenones 6
Entry Nitroalkane
Acceptor
Yield (%)a
of 6
3-Ethyl-2-phenylcyclopent-2-en-1-one (6b)
Rf 0.35 (cyclohexane–EtOAc, 8:2).
IR (film): 1690, 1630, 1600 cm–1.
a
68
NO2
NO2
Ph
1H NMR (CDCl3): = 1.20 (t, 3 H, J = 7.7, CH3CH2), 2.52–2.60
(m, 4 H, MeCH2, CH2CH2CO), 2.67–2.74 (m, 2 H, CH2CH2CO),
7.22–7.44 (m, 5 H, C6H5).
13C NMR (CDCl3): = 208.09 (C=O), 176.97 (C=CCO), 139.95
(C=CCO), 129.11(CPh), 128.61 (2 C, CHo-Ph), 128.31 (CHp-Ph),
127.63 (2 C, CHm-Ph), 34.70 (CH2CO), 28.63 (CH2CH2CO), 24.89
(CH2Me), 12.24 (CH2CH3).
O
1e
2a
b
65
Ph
O
1e
2b
c
78
NO2
p-Tol
MS: m/z (%) = 186 (M+), 129 (100), 115.
O
1f
Anal. Calcd for C13H14O: C, 83.83; H, 7.58. Found: C, 83.91; H,
7.50.
2a
a Yield of pure, isolated product.
3-Methyl-2-(4-methylphenyl)cyclopent-2-en-1-one (6c)
Rf 0.34 (cyclohexane–EtOAc, 8:2).
IR (film): 1680, 1630 cm–1.
1H and 13C NMR were recorded in CDCl3 at 200 and 50 MHz, re-
spectively, on a Varian Gemini 200 spectrometer. Chemical shifts
are expressed in ppm downfield from TMS. Mass spectra were de-
termined on a Capillary GC/MS operating in the split mode with He
carrier gas with a mass-selective detector (MDS). IR spectra were
recorded on a Perkin-Elmer 257 spectrophotometer. Elemental
analyses were performed using a C, H Analyzer Model 185 from
Hewlett-Packard. All the reactions were monitored by TLC, and gas
chromatographic analyses were performed on a Carlo Erba Frac-
tovap 4160 using a capillary column of duran glass (0.32 mm 25
m), stationary phase OV1 (film thickness 0.4–0.45 m). Petroleum
ether used had bp 30–60 °C.
1H NMR (CDCl3): = 2.20 (s, 3 H, =CCH3), 2.38 (s, 3 H, ArCH3),
2.53–2.59 (m, 2 H, COCH2CH2), 2.64–2.71 (m, 2 H, COCH2CH2),
7.17–7.30 (m, 4 Harom).
13C NMR (CDCl3): = 208.02 (C=O), 171.45 (C=CCO), 140.48
(C=CCO), 137.57 (CAr next to cyclopentenone ring), 129.21 (CAr
substituted with the CH3 group), 129.10 (2 C, CHm-Ar), 129.03 (2 C,
CHo-Ar), 35.01 (CH2CO), 31.98 (CH2CH2CO), 21.48 (ArCH3),
18.55 (=CCH3).
MS: m/z (%) = 186 (M+), 143 (100), 128, 115.
Anal. Calcd for C13H14O: C, 83.83; H, 7.58. Found: C, 83.77; H,
7.66.
-Diketones 4 and -Keto Esters 5; General Procedure
A solution of the electrophilic acceptor 2a or 3 (5 mmol) in MeCN
(10 mL) was added dropwise to a solution of nitroalkane 1a–e (5
mmol) in MeCN (20 mL) at r.t. The reaction mixture was stirred at
r.t. for 6 h, then heated at 60 °C. After 7 d, the solvent was removed
under reduced pressure and the oily residue was purified by flash
chromatography (EtOAc–petroleum ether as eluent), affording the
pure compounds 4 or 5 (Tables 1, 2).
Acknowledgment
Financial support was carried out in the framework of the National
Project ‘Stereoselezione in Sintesi Organica. Metodologie ed Ap-
plicazioni’ supported by MIUR (Ministero dell’Istruzione dell’Uni-
versità e della Ricerca), Italy and by the University of Camerino.
Cyclopentenones 6; General Procedure
References
A solution of the conjugated enone 2 (5 mmol) in MeCN (10 mL)
was added dropwise to a solution of 2-aryl-1-nitroethane deriva-
tives 1e,f (5 mmol) in MeCN (20 mL) at r.t. The obtained solution
was stirred at r.t. for 6 h, then heated at 60 °C. After 3 d, the solvent
was removed under reduced pressure and the oily residue was puri-
fied by flash chromatography (EtOAc–petroleum ether as eluent),
affording the pure compounds 6 (Table 3).
(1) Hall, N. Science 1994, 266, 32.
(2) (a) Lever, O. W. Jr. Tetrahedron 1976, 32, 1943.
(b) Bossard, P.; Engster, C. H. Adv. Heterocycl. Chem. 1986,
30, 384.
(3) Dean, F. M. Adv. Heterocycl. Chem. 1982, 30, 172.
(4) Sundberg, R. J. In Comprehensive Heterocyclic Chemistry,
Vol. 4; Katritsky, A. R.; Rees, C. W., Eds.; Pergamon:
Oxford, 1984, 329.
3-Methyl-2-phenylcyclopent-2-en-1-one (6a)
Rf 0.32 (cyclohexane–EtOAc, 8:2).
IR (film): 1690, 1635 cm–1.
1H NMR (CDCl3): = 2.21 (s, 3 H, CH3), 2.55–2.61 (m, 2 H,
CH2CH2CO), 2.67–2.73 (m, 2 H, CH2CH2CO), 7.25–7.49 (m, 5 H,
C6H5).
13C NMR (CDCl3): = 207.63 (C=O), 171.80 (C=CCO), 140.36
(C=CCO), 129.11 (CPh), 128.28 (2 C, CHo-Ph), 127.81 (CHp-Ph),
127.60 (2 C, CHm-Ph), 34.84 (CH2CO), 31.83 (CH2CH2CO), 18.38
(CH3C=C).
(5) Ellison, R. A. Synthesis 1973, 397.
(6) Ho, T. L. Synth. Commun. 1974, 4, 265.
(7) Stetter, H.; Kuhlmann, H. Org. React. 1991, 40, 407.
(8) See for example: (a) Cardellach, J.; Font, J.; Ortuno, R. M. J.
Heteroycl. Chem. 1984, 21, 327. (b) Short, K. M.; Mjalli,
M. M. A. Tetrahedron Lett. 1997, 38, 359. (c) Frenette, R.;
Monette, M.; Bernstein, M. A.; Young, R. N.; Verhoeven, I.
R. J. Org. Chem. 1991, 56, 3083. (d) Ohkuma, T.;
Kitamura, M.; Noyori, R. Tetrahedron Lett. 1990, 31, 5509.
(9) (a) Mikolajaczyc, M.; Mikina, M.; Zurawinski, R. Pure
Appl. Chem. 1999, 71, 473. (b) Collins, P. E.; Djuric, S. W.
Chem. Rev. 1993, 93, 1533. (c) Noyori, R.; Suzuki, M.
Angew. Chem., Int. Ed. Engl. 1984, 23, 847.
MS: m/z (%) = 172 (M+), 157, 129 (100), 115.
Synthesis 2002, No. 18, 2725–2728 ISSN 0039-7881 © Thieme Stuttgart · New York