EtOH/Ba(OH)2 triggers self-condensation of (E)-1,4-diaryl-2- butene-1,4-diones to cyclopentanol derivatives

Article abstract of DOI:10.1081/SCC-200061715

Several stereo-defined penta-substituted cyclopentanols were synthesized from EtOH/Ba(OH)₂-induced self-condensation of (E)-1,4-diaryl-2- butene-1,4-diones formed via domino pathways. Copyright Taylor & Francis, Inc.

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EtOH/Ba(OH)2 Triggers
Self‐Condensation of
(E)‐1,4‐Diaryl‐2‐Butene‐1,4‐Diones
to Cyclopentanol Derivatives
H. Surya Prakash Rao a & S. P. Senthilkumar a
a Department of Chemistry , Pondicherry University ,
Pondicherry, India
Published online: 16 Aug 2006.
To cite this article: H. Surya Prakash Rao & S. P. Senthilkumar (2005) EtOH/Ba(OH)2
Triggers Self‐Condensation of (E)‐1,4‐Diaryl‐2‐Butene‐1,4‐Diones to Cyclopentanol
Derivatives, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 35:12, 1707-1714, DOI: 10.1081/
SCC-200061715
To link to this article: http://dx.doi.org/10.1081/SCC-200061715
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Synthetic Communicationsw, 35: 1707–1714, 2005
Copyright # Taylor & Francis, Inc.
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1081/SCC-200061715
EtOH/Ba(OH)2 Triggers Self-Condensation
of (E)-1,4-Diaryl-2-Butene-1,4-Diones to
Cyclopentanol Derivatives
H. Surya Prakash Rao and S. P. Senthilkumar
Department of Chemistry, Pondicherry University, Pondicherry, India
Abstract: Several stereo-defined penta-substituted cyclopentanols were synthesized
from EtOH/Ba(OH)2-induced self-condensation of (E)-1,4-diaryl-2-butene-1,4-diones
formed via domino pathways.
Keywords: Barium hydroxide, 1,4-diaryl-2-butene-1,4-diones, domino reactions
The a,b-unsaturated carbonyl compounds have emerged as test systems to
study the multicomponent condensation reactions involving the domino
process.[1] In the domino reaction, the starting material undergoes a series
of transformations in which the functional group generated in the first step
serves to form the next bond in the subsequent step.[2] We have earlier
reported that in the presence of barium hydroxide the enolate anion from
cyclopentanone triggers multicomponent condensation of (E)-1,3-diaryl-2-
propene-1-one (trans-chalcone) and phenyl vinyl ketone to furnish polycyclic
products.[3] In continuation, EtOH/Ba(OH)2-mediated self-condensation of
(E)-1,4-diphenyl-2-butene-1,4-dione (trans-dibenzoylethylene, trans-DBE)
to the cyclopentanol derivative has been presented here (Scheme 1).
Previously, Cabrera and coworkers have reported the formation of some
Received in India November 2, 2004
Address correspondence to H. Surya Prakash Rao, Department of Chemistry,
Pondicherry University, Pondicherry 605 014, India. E-mail: hspr@yahoo.com
1707

1708
H. S. P. Rao and S. P. Senthilkumar
Scheme 1.
tetrasubstituted cyclopentanol derivatives from trans-DBE in the presence of
the one-electron reducing agent samarium (II) iodide.[4] Similarly, Al-Arab
and co-workers reported the formation of cyclohexanol derivates from the
base-mediated reaction of acetophenone with DBE.[5]
While attempting the condensation of cyclohexanone and trans-DBE in
the presence of activated Ba(OH)2, we noticed the formation of a polar
product (6%) apart from the expected conjugate addition product (63%).[6]
When the condensation reaction was conducted in the absence of cyclo-
hexanone, the polar product was formed in 67% yield (Scheme 1). Its
1H NMR and 13C NMR spectra revealed the presence of least three diastereo-
meric cyclopentanols in the ratio of 61:28:11. The ratio of the diasteromers
was determined on the integration of the cluster of signals located at
1
d 5.7 ppm in the H NMR spectrum assignable to 5-H and the cluster of
signals located at d 90 ppm assignable to C-3. The major diastereomer 2a
was isolated in the pure form through fractional crystallization from the
column fractions during column chromatography.
The structure and stereochemistry of the cyclopentanol derivative 2a,
obtained as a white crystalline solid (mp 184–1868C) was deduced on the
basis of analytical and spectral data (IR, 1H NMR, 13C NMR, DEPT,
COSY, and NOESY). Final confirmation of the proposed structure of 2a
was obtained by X-ray analysis (Figure 1) on the sample recrystallized from
10% EtOAc in hexanes. (See the Appendix.)
Having established the structure of the cyclopentanol derivative 2a, the
generality of the reaction was next studied by subjecting different trans-
DBE derivatives with electron-withdrawing (Cl, 1b, Br, 1c) and electron-
donating (Me, 1d) groups located on the para position of the aryl rings to
self-condensation. The reactions furnished cyclopentanol products 2b–d in
64–72% yield. Although pure cyclopentanols 2b and 2c could be isolated
from the fractional crystallization their respective mixture of isomers, 2d
could not be obtained as a single product by different chromatographic or
recrystallization techniques.
Surprisingly, the present three-component condensation reaction
involving two units of trans-DBE 1a and the alkoxide anion did not take
place with MeOH/Ba(OH)2. Only conjugate addition product 6 was
isolated from the reaction in moderate yield (34%; Scheme 2).[7]

EtOH/Ba(OH)2
1709
Figure 1. Crystal structure of [(1R,2S,3S,4S,5R)-4,5-dibenzoyl-2-ethoxy-3-hydroxy-
3-phenylcyclopentyl](phenyl)methanone (2a, with crystal structure numbering;
hydrogens were omitted for clarity).
The Ba(OH)2-mediated three-component domino reaction of 1a was
attempted with azide, cyanide, and nitromethane anions. Although the nitro-
methane added to trans-DBE 1a in conjugate mode to furnish known
diketone 8[8] (54%, Scheme 2), the product from the conjugate addition of
Scheme 2.

1710
H. S. P. Rao and S. P. Senthilkumar
azide anion underwent further reduction to yield known 2-amino-1,4-
diphenylbut-2-ene-1,4-dione 7[9] (58%, Scheme 2). We did not notice any
cyclopentanol products from these reactions. The reaction of 1a with
cyanide anion in the presence of activated Ba(OH)2 furnished a complex
mixture along with conjugate addition product 9.[10] Surprisingly there was
no Ba(OH)2-mediated reaction of trans-DBE 1a with thiophenol or
heptanethiol.
In short, we have shown that EtOH/Ba(OH)2 induces self-condensation
of trans-DBE and its derivatives to furnish penta-substituted cyclopentanol
derivatives with defined stereochemistry. It appears that the cyclopentanol
formation is induced only in the presence of EtOH/Ba(OH)2.
EXPERIMENTAL
General
The progress of all the reactions was monitored by TLC (TLC silica gel;
Qualigens or TLC alumina: SRL, India) using hexanes/ethyl acetate
mixture as an eluent. Column chromatography was accomplished on silica
gel (100–200 mesh, Acme Synthetic Chemicals) using hexanes/ethyl
acetate mixture as an eluent. The IR spectra were recorded as a solution in
KBr or neat using ABB Bomem MB-104 FT-IR spectrometer. The
1H NMR and 13C NMR spectra were recorded in CDCl3 or CDCl3 CCl4
.
(1:1) using JEOL 400-MHz or Varian 300-MHz NMR spectrometer. The
mass spectra were recorded on Finnigan MAT 8230 or JEOL DX-303 mass
spectrometer. The elemental analysis was carried out on a Elementar vario
EL (Germany) apparatus. The X-ray diffraction data was generated on
SMART (Siemens) diffractometer. The trans-DBE and derivatives (1a–d)
were prepared according to literature procedure.[11] The activated Ba(OH)2
.
was prepared by heating commercial Ba(OH)2 8H2O at 2008C for 3 h in a
furnace and then stored in a desiccator.[12]
Synthesis of (+) [(1R,2S,3S,4S,5R)-4,5-dibenzoyl-2-ethoxy-3-hydroxy-3-
phenylcyclopentyl](phenyl)methanone 2a; representative procedure: To a
stirred mixture of activated Ba(OH)2 (73 mg, 0.43 mmol) in 10 mL of
absolute ethanol, trans-DBE 1a (500 mg, 2.12 mmol) was added in four
equal portions and allowed to stir at room temperature for 12 h. After
complete disappearance of 1a (TLC), the suspended solid particles were
filtered through a celite pad. The clear filtrate was concentrated to 3 mL and
was diluted with 30 mL of dichloromethane and then poured over ice-
cooled water. The organic layer was separated, washed again with water
(3 ꢀ 20 mL) and brine solution (2 ꢀ 10 mL), dried over anhydrous Na2SO4,
and concentrated. The crude product was subjected to column

EtOH/Ba(OH)2
1711
chromatography (silica gel, 100–200 mesh) and eluted with 10% EtOAc–
hexanes to give 2a (63 mg, 12%) as a crystalline solid. Mp 184–1868C;
Rf ¼ 0.43 (10% EtOAc–hexanes); IR (KBr) 3466, 1683, 1596, 1449, 1258,
709, 691 cm21
;
1H NMR (300 MHz, CDCl3) d 0.68 (t, J ¼ 7.2 Hz, 3H),
2.85 (m, 1H), 3.09 (m, 1H), 4.20 (s, 1H), 4.49 (d, J ¼ 7.8 Hz, 1H), 4.55
(d, J ¼ 10.5 Hz, 1H), 4.78 (dd, J ¼ 7.8, 10.5 Hz, 1H), 5.76 (t, J ¼ 10.2 Hz,
1H), 7.05 (t, J ¼ 7.8 Hz, 2H), 7.21–7.54 (m, 14H), 7.89 (d, J ¼ 8.7 Hz,
2H), 8.26 (d, J ¼ 8.7 Hz, 2H) ppm; 13C NMR (75 MHz, CDCl3) d 14.6,
46.1, 54.8, 62.3, 68.9, 82.7, 89.7, 124.8, 127.3, 127.8, 128.0, 128.3, 128.5
(2C), 128.6, 129.4, 132.4, 133.1, 133.6, 136.2, 137.2, 137.3, 144.7, 196.9,
197.5, 202.5 ppm; FAB-MS 519 (Mþ þ 1); Anal. calcd. for C34H30O5:
C, 78.74; H, 5.83. Found: C, 78.77; H, 5.87.
(+) (4-Chlorophenyl)[(1R,2S,3S,4S,5R)-4,5-di(4-chlorobenzoyl)-3-(4-chloro-
phenyl)-2-ethoxy-3-hydroxycyclopentyl]methanone 2b: Mp 168–1708C;
Rf ¼ 0.36 (10% EtOAc–hexanes); IR (KBr) 3466, 2975, 2929, 1684, 1588,
1489, 1401, 1247, 1093, 1006, 840 cm21 1H NMR (300 MHz, CDCl3/
;
CCl4) d 0.76 (t, J ¼ 6.9 Hz, 3H), 2.81–2.91 (m, 1H), 3.06–3.16 (m, 1H),
4.04 (s, 1H), 4.30 (d, J ¼ 10.8 Hz, 1H), 4.35 (d, J ¼ 9.9 Hz, 1H), 4.60
(t, J ¼ 7.5 Hz, 1H), 5.56 (t, J ¼ 10.2 Hz, 1H), 7.07 (d, J ¼ 8.4 Hz, 2H), 7.24
(d, J ¼ 8.1 Hz, 2H), 7.31 (d, J ¼ 8.1 Hz, 2H), 7.39–7.50 (m, 6H), 7.81
(d, J ¼ 8.4 Hz, 2H), 8.16 (d, J ¼ 8.4 Hz, 2H) ppm; 13C NMR (75 MHz,
CDCl3/CCl4) d 14.98, 45.86, 54.60, 62.44, 69.04, 82.53, 89.73, 126.38,
128.29, 129.00, 129.15, 129.51, 129.77, 130.21, 131.15, 133.87, 134.29,
135.50, 135.61, 139.33, 139.87, 140.63, 143.37, 194.65, 195.09,
200.72 ppm; LRMS Mþ did not appear, 639 (7), 517 (19), 515 (30), 497
(18), 468 (29), 447 (15), 445 (35), 443 (27), 428 (20), 364 (31), 348 (24),
348 (18), 307 (69), 305 (100), 304 (74), 181 (12), 183 (7), 113 (27), 111
(78), 89 (19), 75 (55), 69 (18); Anal. calcd. for C34H24Cl4O5: C, 62.24;
H, 3.99. Found: C, 62.21; H, 4.02.
(+) (4-Bromophenyl)[(1R,2S,3S,4S,5R)-4,5-di(4-bromobenzoyl)-3-(4-bromo-
phenyl)-2-ethoxy-3-hydroxycyclopentyl]methanone 2c: Mp 176–1788C;
Rf ¼ 0.38 (10% EtOAc–hexanes); IR (KBr) 3496, 2971, 2927, 1671, 1585,
1
1486, 1398, 1234, 1096, 1073, 1003, 980, 834 cm21; H NMR (300 MHz,
CDCl3/CCl4) d 0.71 (t, J ¼ 14.1 Hz, 3H), 2.82–2.92 (m, 1H), 3.03–3.13
(m, 1H), 4.07 (s, 1H), 4.36 (d, J ¼ 10.8 Hz, 1H), 4.41 (d, J ¼ 7.8 Hz, 1H),
4.62 (t, J ¼ 18.0 Hz, 1H), 5.61 (t, J ¼ 20.4 Hz, 1H), 7.17 (d, J ¼ 7.5 Hz,
2H), 7.25 (d, J ¼ 8.1 Hz, 2H), 7.38 (d, J ¼ 8.1 Hz, 2H), 7.46 (d, J ¼ 8.7 Hz,
2H), 7.60 (dd, J ¼ 6.3, 4.8 Hz, 4H), 7.74 (d, J ¼ 8.4 Hz, 2H), 8.11
(d, J ¼ 8.4 Hz, 2H) ppm; 13C NMR (75 MHz, CDCl3/CCl4) d 14.64, 45.81,
54.56, 62.29, 69.14, 82.40, 89.32, 121.74, 126.60, 127.94 (2C), 128.55
(2C), 129.44, 129.64, 130.97, 131.23, 131.84, 131.96, 132.11, 134.71,
135.91, 143.41, 195.42, 196.10, 201.24 ppm; LRMS Mþ peak did not

1712
H. S. P. Rao and S. P. Senthilkumar
appear, 338 (20), 228 (100), 216 (12), 117 (10), 117 (38), 90 (40), 57 (42);
Anal. calcd. for C34H24Br4O5: C, 48.94; H, 3.14. Found: C, 48.91; H, 3.19.
(+) [2-Ethoxy-3-hydroxy-4,5-di(4-methylbenzoyl)-3-(4-methylphenyl)cyclo-
pentyl](4-methylphenyl)methanone 2d: Mp 200–2028C; Rf ¼ 0.40 (10%
EtOAc–hexanes); IR (KBr) 3463, 2923, 2853, 1670, 1606, 1573, 1463,
1
1377, 1240, 1182, 1104, 1006, 828, 721 cm21; H NMR (300 MHz, CDCl3/
CCl4, 1:1) d 0.76 (t, J ¼ 7.5 Hz, 3H), 2.28 (s, 3H), 2.31 (s, 3H), 2.37
(s, 3H), 2.44 (s, 3H), 2.86–2.91 (m, 1H), 3.09–3.17 (m, 1H), 4.15 (s, 1H),
4.31 (d, J ¼ 7.2 Hz, 1H), 4.40 (d, J ¼ 7.8 Hz, 1H), 4.58 (dd, J ¼ 5.7,
13.8 Hz, 1H), 5.59 (t, J ¼ 10.2 Hz, 1H), 6.81–6.86 (m, 2H), 7.07–7.29
(m, 4H), 7.42–7.53 (m, 2H), 7.75–7.85 (m, 4H), 7.95 (d, J ¼ 8.40 Hz, 2H),
8.08 (d, J ¼ 8.40 Hz, 2H) ppm; 13C NMR (75 MHz, CDCl3/CCl4, 1:1) d
15.38, 21.09, 21.25 (2C), 21.79, 47.05, 56.24, 62.71, 68.66, 83.00, 90.42,
125.03, 126.02, 128.34, 128.47, 128.95, 129.16, 129.29, 129.84, 132.98,
134.08, 135.07, 136.20, 138.28, 139.90, 142.85, 145.10, 196.01, 199.98,
201.71 ppm; FAB-MS 575 (Mþ þ 1); Anal. calcd for C38H38O5: C, 79.44;
H, 6.66. Found: C, 79.42; H, 6.69.
2-Methoxy-1,4-diphenyl-1,4-butanedione 6: Rf ¼ 0.38 (10% EtOAc–
hexanes); IR (KBr) 763, 841, 1005, 1250, 1401, 1489, 1588, 1683, 2929,
1
2977, 3070 cm21; H NMR (400 MHz, CDCl3) d 1.83 (t, J ¼ 6.35 Hz, 1H),
2.31 (t, J ¼ 6.35 Hz, 1H), 3.41 (s, 3H), 5.39 (dd, J ¼ 4.39, 11.72 Hz, 1H),
7.41–7.59 (m, 6H), 7.95 (d, J ¼ 7.81 Hz, 2H), 8.04 (d, J ¼ 7.81 Hz, 2H);
13C NMR (100 MHz, CDCl3) d 40.62, 57.80, 78.59, 127.58, 128.21, 128.32,
128.35, 133.42, 133.53, 135.06, 136.53, 196.72, 199.60 ppm.
(Z)-2-Amino-1,4-diphenyl-2-butene-1,4-dione 7: Mp 132–1348C (lit.[9] 133–
1348C); Rf ¼ 0.48 (10% EtOAc–hexanes); IR (KBr) 3378, 3269, 1664, 1613,
1
1593, 1527, 1445, 1275, 1239, 1172, 768, 725 cm21; H NMR (300 MHz,
CDCl3) d 6.23 (s, 1H), 7.39–7.56 (m, 4H), 7.66 (t, J ¼ 14.86 Hz, 2H), 7.82
(t, J ¼ 8.61 Hz, 2H), 7.88 (t, J ¼ 8.66 Hz, 2H), 9.5 (br s, 2H) ppm;
13C NMR (75 MHz, CDCl3) d 97.63, 127.37, 128.51, 128.58, 129.81,
131.96, 133.41, 135.42, 139.28, 152.57, 191.75, 193.63 ppm.
2-(Nitromethyl)-1,4-diphenyl-1,4-butanedione 8: Mp 93–948C (lit.[8] 958C);
Rf ¼ 0.30 (10% EtOAc–hexanes); IR (KBr) 3066, 2978, 1679, 1552, 1447,
1416, 1386, 1253, 1216, 984, 961, 757, 691 cm21 1H NMR (300 MHz,
;
CDCl3) d 3.25 (dd, J ¼ 6.91, 7.40 Hz, 1H), 3.55 (dd, J ¼ 4.76, 1.58 Hz,
1H), 4.60–4.68 (m, 1H), 4.88–4.96 (m, 2H), 7.44–7.63 (m, 6H), 7.91
(d, J ¼ 8.69 Hz, 2H), 8.04 (d, J ¼ 8.74 Hz, 2H) ppm; 13C NMR (75 MHz,
CDCl3) d 37.99, 39.5, 74.62, 128.12, 128.66, 128.84, 129.06, 133.95, 134.0,
134.91, 135.69, 195.81, 198.46 ppm.

EtOH/Ba(OH)2
1713
APPENDIX
Crystal structure analysis was carried out by Professor H.-K. Fun, Universiti
Sains Malaysia, Malaysia. Crystal data and experimental crystallographic
details for 2a; Cambridge Crystallographic Data Center, deposition no.
CCDC 226255.
Empirical formula
Formula weight
Temperature
C34H30O5
518.58
293(2) K
0.71073
Triclinic, P-1
Wavelength
Crystal system, space group
Unit cell dimensions
a ¼ 11.0603(4) A a ¼ 108.079(1) deg.
b ¼ 11.2631(4) A b ¼ 91.207(1) deg.
c ¼ 12.4962(4) A g ¼ 106.913(1) deg.
3
˚
Volume
1405.18(8) A
z, calculated density
Absorption coefficient
F(000)
2, 1.226 Mg/m3
0.081 mm21
548
Crystal size
0.40 ꢀ 0.32 ꢀ 0.24 mm
1.73 to 29.37 deg.
Theta range for
data collection
Limiting indices
213 ꢁ h ꢁ 15, 29 ꢁ k ꢁ 15,
217 ꢁ l ꢁ 16
Reflection collected/unique
Completeness to theta ¼ 29.37
Absorption correction
Refinement method
Data/restraints/parameters
Goodness of fit
10071/6641 [R(int) ¼ 0.0499]
85.7%
None
Full-matrix least-squares on F2
6641/0/352
0.882
Final R indices
[I . 2 sigma(I)]
R1 ¼ 0.0657, wR2 ¼ 0.1516
R indices (all data)
Largest diff. peak and
hole/eA23
R1 ¼ 0.1400, wR2 ¼ 0.1803
0.272 and –0.287
ACKNOWLEDGMENT
SPSK thanks CSIR, India for fellowship. HSPR thanks UGC-SAP and CSIR,
India, for financial support. The authors thank A. Srikrishna, Hans Scheeren,
and SIF, IISc, Bangalore, for recording spectra. The authors also thank
H.-K. Fun, Universiti Sains Malaysia, Malaysia, for solving X-ray crystal
structure. X-ray data was deposited in Cambridge Crystallographic Data
Centre, No: CCDC 226255.

1714
H. S. P. Rao and S. P. Senthilkumar
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