J. CHEM. RESEARCH (S), 1997 307
Table 2 Cyclization of 2,6-diones with aq. HCl
(10%; 100 mg) under hydrogen atmosphere at room temperature
for 3 h. The reaction mixture was filtered and the catalyst was
washed with the same solvent. The combined filtrates were concen-
trated in vacuo to yield compound 2a (540 mg), vmax/cmꢂ1 (neat)
1711; dH (60 MHz, CDCl3) 3.2 (1 H, m), 2.1 (6 H, s, 2-COCH3), 1.15
(3 H, d, J 6 Hz), 2.3–1.5 (4 H, m).
Entry Compound Time (t/h) Yield (%) Products (ratio)
1
2
3
4
5
1
5
5
4
9
3
8a,b
50
91
87
87
3ǹ4 (1:2)
1
5ǹ6 (1:1.2)c
2a
2b
2c
7aǹ8a (3:2) (R = Me)
7 (R = H)
We thank CSIR, New Delhi, for a research grant
(1/1278/93-EMR-II) and RSIC Bombay, Dr P. K. Inamdar,
Hoechst India Ltd., and Nina Pipaliya, S. H. Kelkar Bros.,
Bombay, for spectral data.
7cǹ8c (3:2) (R = COMe)c
aNo starting material was recovered; compound 1 polymerizes.
bCyclization was carried out in sealed tube at 200 °C in 4
M
HCl
(1.5 ml) and light petroleum (0.75 ml). cCould not be separated
by column chromatography; characterized through GC–MS and
spectral properties of the mixture.
Received, 10th July 1996; Accepted, 7th May 1997
Paper E/6/04851J
unique method for the synthesis of dimethylphenols and
a,b-unsaturated cyclohexenones.
References cited in this synopsis
1 P. B. Venuto, Microporus Mater., 1994, 2, 297.
2 W. F. Holderich and H. van Bekkum, in Introduction to Zeolite
Science and Practice, ed. H. Van Bekkum, E. M. Flaningen and
J. C. Jansen, Elsevier, Amsterdam, 1991, p. 631.
3 R. M. Dessau, Zeolites, 1990, 10, 205.
4 V. K. Eiter, in Progress in the Chemistry of Organic Natural
Products, ed. W. Hertz, H. Grisebach and A. I. Scott, Springer
Verlag, Wien, New York, 1970, vol. 28, p. 204.
Experimental
1H NMR spectra were recorded at 60 MHz on Hitachi R-600 and
Bruker WM-500 FT-NMR spectrometers. IR spectra were
recorded on a Perkin Elmer 681 spectrometer. Mass spectra were
recorded with Hewlett Packard (GC-5890, MS-5972) spectrometer
at 70 eV. Column chromatography was done on silica gel (100–200
mesh), slurry packed, employing increasing amounts of ethyl
acetate in light petroleum (bp 60–80 °C) as eluting solvent.
(a) General Procedure for Cyclization of 2,6-Diones over H-ZSM-
5.sA mixture of the 2,6-dione (4 mmol), the zeolite (200 mg) and
dry benzene (2 ml) was heated in a sealed glass tube at 473 K for
5 h. The catalyst was filtered off and washed with ethyl acetate
(5Å5 ml) and the combined filtrates were concentrated under
reduced pressure. The residue was subjected to column chroma-
tography over silica gel to yield the products (Table 1).
5 A. R. Pinder, in Progress in the Chemistry of Organic Natural
Products, ed. W. Herz, H. Grisebach and G. W. Kirby, Springer
Verlag, Wien, New York, 1977, vol. 34, p. 81.
6 Y. Kurahashi and S. Tsubi, Jpn. Pat., 04 261 1089, 1992.
7 V. P. Vitullo, J. Org. Chem., 1970, 35, 3976.
8 J. N. Marx, J. C. Argyle and L. R. Norman, J. Am. Chem. Soc.,
1974, 96, 2121.
9 G. Rao, S. Rangaraja and M. V. Bhatt, J. Chem. Soc., Chem.
Commun., 1974, 584.
(b) Cyclization using Aq. HCl–Light Petroleum.sA mixture of
10 R. F. Parton, J. M. Jacobs, D. R. Huybrechts and P. A. Jacobs,
Stud. Surf. Sci. Catal., 1988, 46, 163.
4
M
HCl (20 ml) and the 2,6-dione (6 mmol) in light petroleum (30
ml) was refluxed with stirring for the period mentioned in Table 2.
After cooling, the two layers were separated and the organic layer
was washed with saturated NaHCO3 solution, and then dried over
Na2SO4. The residue obtained after evaporation of solvent under
reduced pressure was chromatographed over silica gel to yield the
products (Table 2).
11 R. F. Parton, J. M. Jacobs, H. van Ooteghem and P. A. Jacobs,
Stud. Surf. Sci. Catal., 1988, 46, 211.
12 D. Basavaiah, V. V. L. Gowrisswari and T. K. Bharathi, Tetra-
hedron Lett., 1987, 28, 4591.
13 B. C. Ranu and B. Sanjay, Tetrahedron, 1992, 48, 1327.
14 W. Bruce Kover, J. J. Junior, A. P. De Aguiar and M. L. A. von
Holleben, Tetrahedron, 1987, 43, 3199.
Synthesis of 2a.sA stirred solution of the enone 1 (560 mg, 4
mmol) in dry methanol (30 ml) was hydrogenated over Pd–C