Vol. 31, No. 2 (2019)
Ultrasound Assisted Nitratobis(triphenyl phosphine) Conjugate Addition of Alkyl or Aryl Bromides 349
graphy (TLC) was carried out on aluminum sheets precoated
with silica gel. Ultrasound irradiation was performed in an
ultrasonic cleaner with frequency of 33 KHz and a output power
of 250 W. The reaction flasks were located in the maximum
energy area of the cleaner.
Synthesis of nitratobis(triphenyl phosphine)copper(I):
Triphenyl phosphine (0.04 mol,10.5 g) and Cu(NO3)2·2H2O
(0.01 mol, 2.45 g) was added to 100 mL hot methanol. Imme-
diately, Cu(II) dissolves and white suspension formed. This
suspension was refluxed for 10 min and cooled to ambient
temperature. After filtration, washed with ether, ethanol and
dried. Recrystallization from methanol gave colourless solid.
m.p. 232ºC, soluble in DMF, CHCl3, CH2Cl2, CH3CN and THF.
IR (KBr, νmax, cm-1): 3047, 2924, 1538, 1479, 1464, 1384, 1295,
1096, 810, 741, 693.
Preparation of Rieke zinc metal solution: 100 mL two-
neck RBF was flushed by nitrogen. In this flask, a mixture of
0.05 g lithium metal, 0.1 g naphthalene and 5 mL THF was
stirred at room temperature to observed dark green colour
solution. Then, 5 mL saturated solution of ZnCl2 in THF was
added to above dark green colour solution by syringe and
mixture was irradiated for 30 min. the black grey colour zinc
metal solution observed in RBF (Scheme-I).
J = 7.2 Hz, 3H), 3.7 (s, CH3), 4.1 (q, J = 7.2 Hz, CH2), 4.2 (d,
CH, J = 7 Hz), 4.7 (d, CH, J = 7 Hz), 6.8-7.4 (m, 9H, ArH).
13C NMR (125 MHz, CDCl3) δ ppm: 164.5, 158.1, 143.0, 135.5,
129.2, 128.2, 126.2, 166.8, 114.8, 60.8, 55.8, 40.8, 34.6, 14.1.
Anal. Calcd. (found) % for C19H19NO3: C, 73.77 (73.79); H,
6.19 (6.17); N, 4.53 (4.51); O, 15.52 (15.50).
Ethyl 2-cyano-3-(4-methoxy phenyl)-3-( pyridine-2-yl)-
propanoate (5b): Yellow liquid, m.f. C18H18N2O3, IR (KBr,
ν
max, cm-1): 2971 (-C-H), 2242 (-CN), 1733 (-COO), 1591, 1513,
(aromatic C=C), 1110 (-C-O), 1H NMR (500 MHz, CDCl3) δ
ppm: 1.3 (t, CH3, J = 7.2 Hz, 3H), 3.8 (s, CH3), 4.3 (q, J = 7.2
Hz, CH2), 4.4 (d, CH, J = 7 Hz), 4.8 (d, CH, J = 7 Hz), 6.9-8.4
(m, 8H, ArH). 13C NMR (125 MHz, CDCl3) δ ppm: 164.5,
163.4, 157.8, 148.3, 136.4, 132.5, 128.7, 122.9, 121.0, 116.8,
114.2, 60.8, 55.8, 40.8, 34.6, 14.1. Anal. Calcd. (found) % for
C18H18N2O3: C, 69.66 (69.64); H, 5.85 (5.87); N, 9.03 (9.00);
O, 15.47 (15.49).
Ethyl 2-cyano-3-(4-methoxyphenyl)-3-(thiophene-2-yl)-
propanoate (5c): Yellow liquid, m.f. C17H17NO3S, IR (KBr,
ν
max, cm-1): 2978 (-C-H), 2242 (-CN), 1733 (-COO), 1589, 1512,
(aromatic C=C), 1112 (-C-O). 1H NMR (500 MHz, CDCl3) δ
ppm: 1.3 (t, CH3, J = 7.2 Hz, 3H), 3.8 (s, CH3), 4.3 (q, J = 7.2
Hz, CH2), 4.4 (d, CH, J = 7 Hz), 4.8 (d, CH, J = 7 Hz), 6.8-7.4
(m, 7H, ArH). 13C NMR (125 MHz, CDCl3) δ ppm: 164.5,
157.8, 144.7, 132.5, 128.7, 127.0, 126.7, 125.5, 116.8, 114.2, 60.8,
55.8, 41.5, 35.3, 14.1.Anal. Calcd. (found) % for C17H17NO3S:
C, 64.74 (64.76); H, 5.43 (5.46); N, 4.44 (4.42); O, 15.22 (15.20);
S, 10.17 (10.15).
Naphthalene
ZnCl2
Ar-Br
Zn*
+
Li
THF
Zn*
ArZnBr
THF
Ethyl 2-cyano-3-(1H-indol-5-yl)-3-(4-methoxyphenyl)-
propanoate (5d): Yellow liquid, m.f. C21H20N2O3, IR (KBr,
Scheme-I: Synthesis of Rieke zinc metal solution
ν
max, cm-1): 3383 (-NH) 2976 (-C-H), 2241 (-CN), 1732 (-COO),
Preparation of alkyl or aryl zinc bromide and conjugate
addition to α,β-unsaturated cyanoester: Saturated solution
of LiCl ((5 mL) in THF and 5 mmol alkyl or aryl bromide in 2
mL THF was added in zinc metal solution, then irradiated for
30 min, the formation of organozinc takes place, it was confirmed
by TLC. Finally, 5 mmol cyanoester in 2 mL THF and 10 mol
% Cu(I) catalyst were added in reaction mixture. The reaction
mixture was sonicated for 15-25 min at room temperature.
After completion of reaction, saturated NH4Cl solution was
added (2 × 5 mL). The solution extracted with diethyl ether,
washed with brine solution (10 mL) and dried over Na2SO4.
The extract was then concentrated and the crude product was
purified using column chromatography (silica gel, 80 % pet.
ether/20 % EtOAc) to afford pure compound (5a-i). Products
are easily identified by comparision of their spectroscopic data
(Scheme-II).
1589, 1512, (aromatic C=C), 1112 (-C-O), 1H NMR (500 MHz,
CDCl3) δ ppm: 1.3 (t, CH3, J = 7.2 Hz, 3H), 3.8 (s, CH3), 4.3
(q, J = 7.2 Hz, CH2), 4.4 (d, CH, J = 7 Hz), 4.8 (d, CH, J = 7
Hz), 6.9-8.0 (m, 9H,ArH), 9.9 (NH). 13C NMR (125 MHz, CDCl3)
δ ppm: 164.5, 158.1, 141.2, 135.3, 133.0, 129.2, 128.7, 124.3,
119.8, 119.3, 116.8, 114.8, 111.6, 102.4, 60.8, 55.8, 40.8, 35.0,
14.1.Anal. Calcd. (found) % for C21H20N2O3: C, 72.40 (72.43);
H, 5.79 (5.77); N, 8.04 (8.02); O, 13.78 (13.80).
Ethyl 2-cyano-3-(4-methoxy phenyl)-3-(pyrimidin-5-yl)-
propanoate (5e):Yellow liquid, m.f. C17H17N3O3, IR (KBr, νmax
,
cm-1): 2978 (-C-H), 2240 (-CN), 1733 (-COO), 1591, 1512,
(aromatic C=C), 1114 (-C-O). 1H NMR (500 MHz, CDCl3) δ
ppm: 1.3 (t, CH3, J = 7.2 Hz, 3H), 3.8 (s, CH3), 4.3 (q, J = 7.2 Hz,
CH2), 4.4 (d, CH, J = 7 Hz), 4.8 (d, CH, J = 7 Hz), 6.9-9.0 (m,
7H,ArH). 13C NMR (125 MHz, CDCl3) δ ppm: δ 163.0, 157.7,
154.3, 136.9, 133.9, 127.8, 116.1, 114.7, 62.3, 55.5, 40.3, 29.6,
14.1.Anal. Calcd. (found) % for C17H17N3O3: C, 65.58 (65.56);
H, 5.50 (5.48); N, 13.50 (13.52); O, 15.42 (15.40).
Spectral data
Ethyl 2-cyano-3-(4-methoxy phenyl)-3-phenyl propanoate
(5a):Yellow liquid, m.f. C19H19NO3, IR (KBr, νmax, cm-1): 2971
(-C-H), 2240 (-CN), 1732 (-COO), 1591, 1514 (aromatic C=C),
1130 (-C-O). 1H NMR (300 MHz, CDCl3) δ ppm: 1.1 (t, CH3,
Ethyl 2,4-dicyano-3-(4-methoxyphenyl)butanoate (5f):
Yellow liquid, m.f. C15H16N2O3, IR (KBr, νmax, cm-1): 3010
(-C-H), 2238 (-CN), 1732 (-COO), 1589, 1512, (arom. C=C), 1174
H3CO
NC
H3CO
H3CO
10 mol %
CN
Cu(I)
Base
ArZnBr
+
+ NCCH2COOEt
COOEt
THF, room temp.
CHO
COOEt
1
4
2
Ar
3
5
Scheme-II: Synthesis of cyanoester