B. C. Ranu et al. / Tetrahedron 63 (2007) 776–782
781
four products (entries 17, 22, 23 and 26, Table 1) and were
easily identified by comparison of their spectroscopic data
with those reported (Refs. in Table 1). The unknown prod-
ucts were characterized by their spectroscopic (IR, H and
13C NMR) data and elemental analysis. These data are pro-
vided below.
reported. The product in entry 7 was characterized by its
1
spectroscopic (IR, H and 13C NMR) data and elemental
analysis. These data are provided below.
1
4.3.1. 2,3-Bis-ethylsulfanyl-1-phenyl-4-thiophene-2-yl-
butane-1,4-dione (entry 7, Table 2). Brown solid, mp 80–
82 ꢀC; IR (KBr): 1435, 1690, 1702 cmꢁ1; 1H NMR (CDCl3,
300 MHz) d 1.08 (t, J¼7.4 Hz, 3H), 1.20 (t, J¼7.4 Hz, 3H),
2.53–2.70 (m, 4H), 4.78 (d, J¼11.6 Hz, 1H), 4.96 (d,
J¼11.6 Hz, 1H), 7.18–7.74 (m, 5H), 7.89–8.17 (m, 3H);
13C NMR (75 MHz, CDCl3) d 14.0 (2C), 25.2, 25.9, 46.6,
48.4, 128.2, 128.4 (2C), 128.6 (2C), 132.1, 133.3, 134.3,
136.0, 143.1, 186.9, 193.1. Anal. Calcd for C18H20O2S2:
C, 65.02; H, 6.06. Found: C, 64.88; H, 5.92.
4.2.1. 4-Cyano-4-ethoxycarbonyl-heptanedioic acid
dibutyl ester (entry 17, Table 1). Colourless liquid, IR
(neat) 2260, 1739, 1452 cmꢁ1; 1H NMR (300 MHz, CDCl3)
d 0.90 (t, J¼7.3 Hz, 6H), 1.24–1.39 (m, 7H), 1.54–1.63 (m,
4H), 2.29 (t, J¼8.5 Hz, 4H), 2.66 (t, J¼8.5 Hz, 4H), 4.08 (t,
J¼6.7 Hz, 4H), 4.26 (q, J¼7.1 Hz, 2H); 13C NMR (75 MHz,
CDCl3) d 13.9, 19.0 (2C), 24.8 (2C), 30.1 (2C), 30.5 (2C),
32.0 (2C), 36.4, 63.1, 64.8 (2C), 117.9, 164.8, 171.4 (2C).
Anal. Calcd for C19H31O6N: C, 61.77; H, 8.46; N, 3.79.
Found: C, 61.51; H, 8.21; N, 3.89.
4.4. General experimental procedure. Representative
one for alkylation of dibenzoyl methane with benzyl
bromide (entry 1, Table 3)
4.2.2. 4,4-Dicyano-heptanedioic acid dibutyl ester (entry
22, Table 1). Colourless liquid, IR (neat) 2265, 1735,
A mixture of dibenzoyl methane (224 mg, 1 mmol), benzyl
bromide (171 mg, 1 mmol) and [bmIm]OH (250 mg) was
subjected to microwave irradiation (CEM microwave reac-
tor, 100 ꢀC, 1.00 psi) for 5 min (TLC). The product was
extracted with ethyl acetate (2ꢂ10 ml), washed with brine,
dried (Na2SO4) and evaporated to leave a crude product,
which was purified by a short column chromatography
over silica gel (ethyl acetate/pet ether, 20:80) to provide
the pure product, 2-benzyl-1,3-diphenyl-propane-1,3-dione
(273 mg, 87%), as a white solid. The spectroscopic (IR, 1H
and 13C NMR) data are in good agreement with those
reported.12 The remaining ionic liquid was dried under vac-
uum and reused for five reactions without any loss of effi-
ciency. After five runs 50% of fresh ionic liquid was added
to it and this was used again. This procedure was followed
for all the reactions listed in Table 3. The products, except
the one in entry 2, Table 3, are all known compounds and
were identified by comparison of their spectroscopic data
with those reported (Refs. in Table 3). The unknown com-
pound (entry 2) was characterized by its spectroscopic (IR,
1H and 13C NMR) data and elemental analysis. These data
were provided below.
1
1454 cmꢁ1; H NMR d 0.89 (t, J¼7.3 Hz, 6H), 1.31–1.38
(m, 4H), 1.53–1.62 (m, 4H), 2.29 (t, J¼8.5 Hz, 4H), 2.65 (t,
J¼8.5 Hz, 4H), 4.08 (t, J¼6.7 Hz, 4H); 13C NMR d 15.0
(2C), 18.9 (2C), 30.2 (2C), 30.4 (2C), 32.6 (2C), 36.2, 65.1
(2C), 114.3 (2C), 117.4 (2C). Anal. Calcd for C17H26O4N2:
C, 66.33; H, 8.13; N, 8.69. Found: C, 66.04; H, 8.02; N, 8.50.
4.2.3. 4,4-Dicyano-heptanedinitrile (entry 23, Table 1).
Pale brown solid, mp 90–92 ꢀC; IR (KBr) 2251, 2240,
1
1444 cmꢁ1; H NMR d 2.30 (t, J¼4.3 Hz, 4H), 2.60 (t,
J¼4.3 Hz, 4H); 13C NMR d 13.5 (2C), 31.7 (2C), 35.4,
112.6 (2C), 116.3 (2C). Anal. Calcd for C9H8N4: C, 55.05;
H, 16.42; N, 28.53. Found: C, 54.82; H, 16.20; N, 28.44.
4.2.4. 1-(2-Butoxycarbonyl-ethyl)-2-oxo-cyclopentane-
carboxylic acid ethyl ester (entry 26, Table 1). Colourless
liquid, IR (neat) 1742, 1740, 1710 cmꢁ1; 1H NMR d 0.89 (t,
J¼7.4 Hz, 3H), 1.22 (t, J¼7.1 Hz, 3H), 1.25–1.37 (m, 2H),
1.54–1.59 (m, 2H), 1.90–1.98 (m, 4H), 2.19–2.48 (m, 6H),
4.03 (t, J¼6.6 Hz, 2H), 4.13 (q, J¼7.1 Hz, 2H); 13C NMR
d 13.4, 13.9, 19.0, 19.5, 28.3, 29.7, 30.5, 33.5, 37.8, 59.1,
61.4, 64.3, 170.2, 172.9, 214.3. Anal. Calcd for C15H24O5:
C, 63.36; H, 8.51. Found: C, 63.09; H, 8.48.
4.4.1. 2-Butyl-1,3-diphenyl-propane-1,3-dione (entry 2,
Table 3). Viscous liquid, IR (neat) 1693, 1664,
1
4.3. General experimental procedure. Representative
one for Michael addition of ethane dithiol to phenyl
acetylenic ketone (entry 1, Table 2)
1446 cmꢁ1; H NMR d 0.87 (t, J¼6.8 Hz, 3H), 1.32–1.43
(m, 4H), 2.09–2.16 (m, 2H), 5.25 (t, J¼6.6 Hz, 1H), 7.38–
7.43 (m, 4H), 7.47–7.54 (m, 2H), 7.96–7.99 (m, 4H); 13C
NMR d 13.6, 22.5, 29.1, 30.2, 56.7, 126.9, 128.3 (4C),
128.6 (4C), 133.2 (2C), 135.9, 196.0 (2C). Anal. Calcd for
C19H20O2: C, 81.40; H, 7.19. Found: C, 81.32; H, 7.21.
The ionic liquid [bmIm]OH (15 mg, 10 mol %) was added
dropwise to a well stirred mixture of phenyl acetylenic
ketone (130 mg, 1 mmol), ethane dithiol (94 mg, 1 mmol)
and [bmIm]Br (220 mg, 1 mmol), and the reaction mixture
was stirred for 15 min till completion of reaction (TLC).
The reaction mixture was extracted with ethyl acetate,
washed with brine, dried (Na2SO4) and evaporated to leave
the crude product, which was purified by short silica gel col-
umn chromatography to provide the pure adduct (219 mg,
98%) as a white solid. The product was identified by com-
parison of its IR, 1H and 13C NMR spectroscopic data with
those reported.8a All the Michael addition products, except
the one in entry 7, Table 2, are known compounds (Ref. in
Table 2) and were characterized by good agreement of their
spectroscopic (IR, 1H and 13C NMR) data with those
Acknowledgements
This investigation has enjoyed financial support from CSIR
[Grant No. 01(1936)/04], New Delhi. S.B. and R.J. are
thankful to CSIR for their fellowships.
References and notes
1. (a) Welton, T. Chem. Rev. 1999, 99, 2071; (b) Wasserscheid,
P.; Keim, W. Angew. Chem., Int. Ed. 2000, 39, 3773;