Synthesis of N-(5-aryloxymethyl-1,3,4-Thiadiazol-2-yl)-N′-(5-aryl-2-Furoyl) -thioureas under phase transfer catalysis

Article abstract of DOI:10.1081/SCC-120003161

The N-(5-aryloxymethyl-1,3,4-thiadiazol-2-yl)- N-(5,-aryl-2furoyl)-thioureas (4_1-15) are synthesized by the reaction of 5-aryl-2-furoyl chlorides 1 with ammonium thiocyanate and 2-amino-5-aryloxymethyl-1,3,4-thiadiazoles 3 under phase transfer

Full text of DOI:10.1081/SCC-120003161

This article was downloaded by: [The University Of Melbourne Libraries]
On: 15 September 2013, At: 00:49
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,
37-41 Mortimer Street, London W1T 3JH, UK
Synthetic Communications: An International Journal
for Rapid Communication of Synthetic Organic
Chemistry
Publication details, including instructions for authors and subscription information:
http://www.tandfonline.com/loi/lsyc20
SYNTHESIS OF N-(5-ARYLOXYMETHYL-1,3,4-
THIADIAZOL-2-YL)-N′-(5-ARYL-2-FUROYL)-THIOUREAS
UNDER PHASE TRANSFER CATALYSIS
Xicun Wang a , Zheng Li a , Ya Tu a & Yuxia Da a
a Department of Chemistry, Northwest Normal University, Lanzhou, Gansu, 730070, P.R.
China
Published online: 21 Aug 2006.
To cite this article: Xicun Wang , Zheng Li , Ya Tu & Yuxia Da (2002) SYNTHESIS OF N-(5-ARYLOXYMETHYL-1,3,4-THIADIAZOL-2-
YL)-N′-(5-ARYL-2-FUROYL)-THIOUREAS UNDER PHASE TRANSFER CATALYSIS, Synthetic Communications: An International
Journal for Rapid Communication of Synthetic Organic Chemistry, 32:7, 1113-1119, DOI: 10.1081/SCC-120003161
To link to this article: http://dx.doi.org/10.1081/SCC-120003161
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained
in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the
Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and
are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and
should be independently verified with primary sources of information. Taylor and Francis shall not be liable for
any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever
or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of
the Content.
This article may be used for research, teaching, and private study purposes. Any substantial or systematic
reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any
form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://
www.tandfonline.com/page/terms-and-conditions

SYNTHETIC COMMUNICATIONS, 32(7), 1113–1119 (2002)
SYNTHESIS OF N-(5-ARYLOXYMETHYL-
1,3,4-THIADIAZOL-2-YL)-N0-(5-ARYL-2-
FUROYL)-THIOUREAS UNDER PHASE
TRANSFER CATALYSIS
*
XicunWang, Zheng Li,
Ya Tu, and Yuxia Da
Department of Chemistry, Northwest Normal
University, Lanzhou, Gansu, 730070, P.R. China
ABSTRACT
The N-(5-aryloxymethyl-1,3,4-thiadiazol-2-yl)-N0-(5-aryl-2-
furoyl)-thioureas (41–15) are synthesized by the reaction of
5-aryl-2-furoyl chlorides 1 with ammonium thiocyanate and
2-amino-5-aryloxymethyl-1,3,4-thiadiazoles 3 under phase
transfer catalysis.
Substituted thioureas have attracted much attention due to their her-
bicidal,1 antibacterial,2 anti-HIV3 and plant-growth regulating4 activity.
Meanwhile 5-aryl-2-furoic acid derivatives have been used as antibacterial
agent,5 local anesthesia,6 analgesic7 and plant-growth regulators.8 In addi-
tion, substituted 1,3,4-thiadiazoles have also played an important role in
agriculture and medicine due to their diverse biological activities, such as
antimicrobial,9–14 antibacterial,15 anesthetic,16 anticonvulsant,17 cardio-
tonic18 antihypertensive,19 antiinflammatory20 and antiulcer21 activity.
*Corresponding author.
1113
Copyright & 2002 by Marcel Dekker, Inc.
www.dekker.com

1114
WANG ET AL.
With the objective of obtaining new biologically active com-
pounds, we report herein the preparation of a new series of compounds
bearing a thiourea, a 1,3,4-thiadiazole as well as a 5-aryl-2-furoyl
moiety.
Because of steric constraints, the reactivity of the amino group of 2-
amino-5-substituted-1,3,4-thiadiazoles to acylisothiocyanate is very low.
However, we are able to synthesize the title compounds successfully using
the technique of phase transfer catalysis.
Reaction of 5-aryl-2-furoyl chlorides 1 with ammonium thiocyanate
catalyzed by polyethylene glycol-400 (PEG-400) at room temperature
gives 5-aryl-2-furoylisothiocyanates 2, which on reflux with 2-amino-5-
aryloxymethyl-1,3,4-thiadiazoles 3 in acetone afford N-(5-aryloxymethyl-
1,3,4-thiadiazol-2-yl)-N0-(5-aryl-2-furoyl)-thioureas (41–15) in excellent yield
(scheme).
Scheme.
The characterization of compounds 41–15 is based on their IR
1
(KBr), H NMRand elemental analyses. The IRspectra exhibit a charac-
teristically strong absorption at 1158–1191 cmÀ1 attributable to the C¼S
of the thiourea. The carbonyl absorption is observed at 1660–1686 cmÀ1
.
41–15 in d6-dimethylsulfoxide show
The 1H NMRspectral data of
peaks at 12.35–12.60 (NH), 11.72–11.93 (NH) and 5.60–5.68 ppm (CH2).
All elemental analyses of 41–15 are in good agreement with the structure
prepared.

SUBSTITUTED THIOUREAS AND PHASE TRANSFER CATALYSIS
EXPERIMENTAL
1115
IRspectra were recorded using KBr pellets on an Alpha Centauri
FTIRspectrophotometer and 1H NMRspectra on an FT-80A instrument
using (CD3)2SO as solvent and Me4Si as an internal standard. Elemental
analyses were performed on a Carlo-Erba 1106 Elemental Analysis instru-
ment. Melting points were observed in an open capillary tube and uncor-
rected. 5-Aryl-2-furoyl chloride 122 and 2-amino-5-aryloxymethyl-1,3,4-
thiadiazoles 323,24 were prepared according to literature procedures.
Ammonium thiocyanate and PEG-400 were commercially available and
used as received.
General Procedure for Preparation of 41–15
A suspension of 5-aryl-2-furoyl chloride 1 (10 mmol), ammonium thio-
cyanate (1.14 g, 15 mmol) and PEG-400 (0.18 g, 0.45 mmol) in 40 ml of
methylene chloride was stirred for 1 h at room temperature. The resulting
mixture was filtered, and the filtrate evaporated to remove the solvent. To
the residue was added a solution of 2-amino-5-aryloxymethyl-1,3,4-thiadia-
zole 3 (9.5 mmol) in 20 ml of acetone. The resulting solution was refluxed for
another 6 h. Then, the solvent was removed, and the residue recrystallized
from DMF-EtOH-H2O (6 : 3 : 1) to yield 41–15 as crystals. The physical and
spectral results are shown below.
N-(5-Phenyloxymethyl-1,3,4-thiadiazol-2-yl)-N0-(5-(4-chlorophenyl)-2-
furoyl)-thiourea (41): Yield: 91%. m.p.: 226–227ꢀC. 1H NMR(80 MHz,
DMSO-d6) d 12.40 (1H, s, NH), 11.72 (1H, s, NH), 7.1–8.3 (11H, m, Ar-H
and Fu-H), 5.61 (2H, s, CH2). IR(KBr, n cmÀ1): 3426 (N-H), 1661 (C¼O),
1162 (C¼S), 1600, 1475, 1380, 1272, 1043 (C¼C, N¼C-S-C¼N). Anal. calcd
for C21H15N4O3S2Cl: C, 53.56; H, 3.21; N, 11.90. Found: C, 53.77; H, 3.29;
N, 12.13.
N-(5-(2-Methylphenyloxymethyl)-1,3,4-thiadiazol-2-yl)-N0-(5-(4-chloro-
phenyl)-2-furoyl)-thiourea (42): Yield: 86%. m.p.: 196–197ꢀC. 1H NMR
(80 MHz, DMSO-d6) d 12.36 (1H, s, NH), 11.73 (1H, s, NH), 7.1–8.4
(10H, m, Ar-H and Fu-H), 5.60 (2H, s, CH2), 2.22 (3H, s, CH3). IR
(KBr, n cmÀ1): 3451 (N-H), 1660 (C¼O), 1171 (C¼S), 1620, 1580, 1470,
1380, 1283, 1043 (C¼C, N¼C-S-C¼N). Anal. calcd for C22H17N4O3S2Cl: C,
54.48; H, 3.53; N, 11.55. Found: C, 54.29; H, 3.41; N, 11.40.
N-(5-(3-Methylphenyloxymethyl)-1,3,4-thiadiazol-2-yl)-N0-(5-(4-chloro-
phenyl)-2-furoyl)-thiourea (43): Yield: 84%. m.p.: 206–207ꢀC. 1H NMR
(80 MHz, DMSO-d6) d 12.35 (1H, s, NH), 11.74 (1H, s, NH), 7.1–8.4
(10H, m, Ar-H and Fu-H), 5.62 (2H, s, CH2), 2.21 (3H, s, CH3). IR

1116
WANG ET AL.
(KBr, n cmÀ1): 3429 (N-H), 1660 (C¼O), 1158 (C¼S), 1588, 1475, 1368,
1284, 1030 (C¼C, N¼C-S-C¼N). Anal. calcd for C22H17N4O3S2Cl: C,
54.48; H, 3.53; N, 11.55. Found: C, 54.71; H, 3.68; N, 11.70.
N-(5-(4-Methylphenyloxymethyl)-1,3,4-thiadiazol-2-yl)-N0-(5-(4-chloro-
phenyl)-2-furoyl)-thiourea (44): Yield: 86%. m.p.: 204–205ꢀC. 1H NMR
(80 MHz, DMSO-d6) d 12.36 (1H, s, NH), 11.75 (1H, s, NH), 7.1–8.4 (10H,
m, Ar-H and Fu-H), 5.61 (2H, s, CH2), 2.20 (3H, s, CH3). IR(KBr, n cmÀ1):
3415, 3122 (N-H), 1676 (C¼O), 1174 (C¼S), 1604, 1582, 1474, 1380, 1283,
1032 (C¼C, N¼C-S-C¼N). Anal. calcd for C22H17N4O3S2Cl: C, 54.48; H,
3.53; N, 11.55. Found: C, 54.63; H, 3.60; N, 11.67.
N-(5-(4-Methoxylphenyloxymethyl)-1,3,4-thiadiazol-2-yl)-N0-(5-(4-chloro-
phenyl)-2-furoyl)-thiourea (45): Yield: 82%. m.p.: 203–204ꢀC. 1H NMR
(80 MHz, DMSO-d6) d 12.37 (1H, s, NH), 11.76 (1H, s, NH), 7.1–8.4
(10H, m, Ar-H and Fu-H), 5.60 (2H, s, CH2), 3.89 (3H, s, CH3). IR
(KBr, n cmÀ1): 3449 (N-H), 1663 (C¼O), 1168 (C¼S), 1602, 1581, 1471,
1381, 1282, 1040 (C¼C, N¼C-S-C¼N). Anal. calcd for C22H17N4O4S2Cl: C,
52.74; H, 3.42; N, 11.18. Found: C, 52.96; H, 3.58; N, 11.36.
N-(5-(2,4-Dichlorophenyloxymethyl)-1,3,4-thiadiazol-2-yl)-N0-(5-(4-chloro-
phenyl)-2-furoyl)-thiourea (46): Yield: 83%. m.p.: 247–248ꢀC. 1H NMR
(80 MHz, DMSO-d6) d 12.40 (1H, s, NH), 11.77 (1H, s, NH), 7.1–8.4
(10H, m, Ar-H and Fu-H), 5.64 (2H, s, CH2). IR(KBr, n cmÀ1): 3423,
3125 (N-H), 1686 (C¼O), 1160 (C¼S), 1606, 1590, 1470, 1383, 1296, 1034
(C¼C, N¼C-S-C¼N). Anal. calcd for C21H13N4O3S2Cl3: C, 46.72; H, 2.43;
N, 10.38. Found: C, 46.88; H, 2.50; N, 10.50.
N-(5-Phenyloxymethyl-1,3,4-thiadiazol-2-yl)-N0-(5-(2-nitrophenyl)-2-
furoyl)-thiourea (47): Yield: 90%. m.p.: 210–211ꢀC. 1H NMR(80 MHz,
DMSO-d6) d 12.51 (1H, s, NH), 11.89 (1H, s, NH), 7.1–8.2 (11H, m,
Ar-H and Fu-H), 5.63 (2H, s, CH2). IR(KBr, n cmÀ1): 3401, 3186 (N-H),
1675 (C¼O), 1191 (C¼S), 1590, 1480, 1379, 1277, 1040 (C¼C, N¼C-S-
C¼N). Anal. calcd for C21H15N5O5S2: C, 52.38; H, 3.14; N, 14.54.
Found: C, 52.61; H, 3.27; N, 14.76.
N-(5-(2-Methylphenyloxymethyl)-1,3,4-thiadiazol-2-yl)-N0-(5-(2-nitro-
phenyl)-2-furoyl)-thiourea (48): Yield: 91%. m.p.: 213–214ꢀC. 1H NMR
(80 MHz, DMSO-d6) d 12.53 (1H, s, NH), 11.90 (1H, s, NH), 7.1–8.2
(10H, m, Ar-H and Fu-H), 5.69 (2H, s, CH2), 2.23 (3H, s, CH3). IR
(KBr, n cmÀ1): 3410 (N-H), 1679 (C¼O), 1180 (C¼S), 1604, 1473, 1380,
1276, 1044 (C¼C, N¼C-S-C¼N). Anal. calcd for C22H17N5O5S2: C, 53.32;
H, 3.46; N, 14.13. Found: C, 53.51; H, 3.52; N, 14.27.
N-(5-(4-Methylphenyloxymethyl)-1,3,4-thiadiazol-2-yl)-N0-(5-(2-nitro-
phenyl)-2-furoyl)-thiourea (49): Yield: 86%. m.p.: 225–226ꢀC. 1H NMR
(80 MHz, DMSO-d6) d 12.54 (1H, s, NH), 11.88 (1H, s, NH), 7.1–8.3
(10H, m, Ar-H and Fu-H), 5.60 (2H, s, CH2), 2.24 (3H, s, CH3). IR

SUBSTITUTED THIOUREAS AND PHASE TRANSFER CATALYSIS
1117
(KBr, n cmÀ1): 3402 (N-H), 1676 (C¼O), 1178 (C¼S), 1600, 1480, 1381,
1275, 1041 (C¼C, N¼C-S-C¼N). Anal. calcd for C22H17N5O5S2: C, 53.32;
H, 3.46; N, 14.13. Found: C, 51.11; H, 3.36; N, 14.00.
N-(5-(2-Methoxylphenyloxymethyl)-1,3,4-thiadiazol-2-yl)-N0-(5-(2-nitro-
phenyl)-2-furoyl)-thiourea (410): Yield: 87%. m.p.: 214–215ꢀC. 1H NMR
(80 MHz, DMSO-d6) d 12.58 (1H, s, NH), 11.91 (1H, s, NH), 7.1–8.3
(10H, m, Ar-H and Fu-H), 5.68 (2H, s, CH2), 3.91 (3H, s, CH3). IR
(KBr, n cmÀ1): 3420, 3180 (N-H), 1676 (C¼O), 1180 (C¼S), 1603, 1469,
1380, 1276, 1044 (C¼C, N¼C-S-C¼N). Anal. calcd for C22H17N5O6S2: C,
51.66; H, 3.35; N, 13.69. Found: C, 51.89; H, 3.56; N, 13.90.
N-(5-(2,4-Dichlorophenyloxymethyl)-1,3,4-thiadiazol-2-yl)-N0-(5-(2-nitro-
phenyl)-2-furoyl)-thiourea (411): Yield: 87%. m.p.: 189–190ꢀC. 1H NMR
(80 MHz, DMSO-d6) d 12.54 (1H, s, NH), 11.86 (1H, s, NH), 7.1–8.4
(9H, m, Ar-H and Fu-H), 5.66 (2H, s, CH2). IR(KBr, n cmÀ1): 3303,
3120 (N-H), 1675 (C¼O), 1180 (C¼S), 1590, 1481, 1381, 1290, 1041
(C¼C, N¼C-S-C¼N). Anal. calcd for C21H13N5O5S2Cl2: C, 45.83; H,
2.38; N, 12.72. Found: C, 46.01; H, 2.49; N, 12.98.
N-(5-(4-Nitrophenyloxymethyl)-1,3,4-thiadiazol-2-yl)-N0-(5-(2-nitrophe-
nyl)-2-furoyl)-thiourea (412): Yield: 86%. m.p.: 217–218ꢀC. 1H NMR
(80 MHz, DMSO-d6) d 12.60 (1H, s, NH), 11.93 (1H, s, NH), 7.1–8.4
(10H, m, Ar-H and Fu-H), 5.66 (2H, s, CH2). IR(KBr, n cmÀ1): 3403
(N-H), 1680 (C¼O), 1186 (C¼S), 1600, 1471, 1380, 1278, 1041 (C¼C,
N¼C-S-C¼N). Anal. calcd for C21H14N6O7S2: C, 47.91; H, 2.68; N,
15.96. Found: C, 48.16; H, 2.79; N, 16.10.
N-(5-(2-Methylphenyloxymethyl)-1,3,4-thiadiazol-2-yl)-N0-(5-(3-nitro-
phenyl)-2-furoyl)-thiourea (413): Yield: 89%. m.p.: 244–245ꢀC. 1H NMR
(80 MHz, DMSO-d6) d 12.58 (1H, s, NH), 11.89 (1H, s, NH), 7.1–8.3
(10H, m, Ar-H and Fu-H), 5.67 (2H, s, CH2), 2.22 (3H, s, CH3). IR
(KBr, n cmÀ1): 3430, 3133 (N-H), 1669 (C¼O), 1190 (C¼S), 1597, 1486,
1380, 1283, 1034 (C¼C, N¼C-S-C¼N). Anal. calcd for C22H17N5O5S2: C,
53.32; H, 3.46; N, 14.13. Found: C, 53.56; H, 3.60; N, 14.33.
N-(5-(4-Methylphenyloxymethyl)-1,3,4-thiadiazol-2-yl)-N0-(5-(3-nitro-
phenyl)-2-furoyl)-thiourea (414): Yield: 85%. m.p.: 247–248ꢀC. 1H NMR
(80 MHz, DMSO-d6) d 12.56 (1H, s, NH), 11.84 (1H, s, NH), 7.1–8.4
(10H, m, Ar-H and Fu-H), 5.61 (2H, s, CH2), 2.23 (3H, s, CH3). IR
(KBr, n cmÀ1): 3420, 3123 (N-H), 1676 (C¼O), 1175 (C¼S), 1590, 1479,
1381, 1283, 1031 (C¼C, N¼C-S-C¼N). Anal. calcd for C22H17N5O5S2: C,
53.32; H, 3.46; N, 14.13. Found: C, 53.58; H, 3.58; N, 14.29.
N-(5-(4-Methoxylphenyloxymethyl)-1,3,4-thiadiazol-2-yl)-N0-(5-(3-nitro-
phenyl)-2-furoyl)-thiourea (415): Yield: 82%. m.p.: 222–223ꢀC. 1H NMR
(80 MHz, DMSO-d6) d 12.55 (1H, s, NH), 11.86 (1H, s, NH), 7.1–8.4
(10H, m, Ar-H and Fu-H), 5.66 (2H, s, CH2), 3.92 (3H, s, CH3). IR

1118
WANG ET AL.
(KBr, n cmÀ1): 3418, 3120 (N-H), 1671 (C¼O), 1180 (C¼S), 1596, 1478,
1381, 1280, 1030 (C¼C, N¼C-S-C¼N). Anal. calcd for C22H17N5O6S2: C,
51.66; H, 3.35; N, 13.69. Found: C, 51.88; H, 3.60; N, 13.88.
ACKNOWLEDGMENT
The authors thank the Natural Science Foundation of Gansu Province
for the financial support of this work.
REFERENCES
1. Xue, S.J.; Zou, J.S.; Yang, H.J. Chinese Chem. Lett. 2000, 11, 19.
2. Kogen, H.; Tago, K.; Arai, M.; Minami, E.; Masuda, K.; Akiyama, T.
Bioorg. Med. Chem. Lett. 1999, 9, 1347.
3. Dong, Y.H.; Venkatachalam, T.K.; Narla, R.K.; Trieu, V.N.; Sudbeck,
E.A.; Uckun, F.M. Bioorg. Med. Chem. Lett. 2000, 10, 87.
4. Zhang, Y.M.; Wei, T.B.; Wang, X.C.; Yang, S.Y. Indian J. Chem.
Sect. B 1998, 37, 604.
5. Dai, Y.J.; Li, Y.J.; Chen, J.C. Youji Huaxue 1988, 8, 443; Chem. Abstr.
110: 94889.
6. Koretskaya, N.I.; Trubitsksyna, T.K.; Mashkovskii, M.D.; Oleinik,
A.F. Khim. Farm. Zh. 1977, 11, 33; Chem. Abstr. 87: 39715.
7. Burch, H.A.; Write, R.E.; Wright, G.C.; Goldenberg, M.M. J. Pharm.
Sci. 1980, 69, 107.
8. Wei, T.B.; Chen, J.C.; Wang, X.C.; Yang, S.C. Chem. J. Chin. Univ.
(Chinese) 1992, 13, 1217; Chem. Abstr. 118: 191447.
9. Eweiss, N.F.; Bahajaj, A.A. J. Heterocycl. Chem. 1987, 24, 1173.
10. Shah, V.H.; Patel, H.H.; Parikh, A.R. J. Indian Chem. Soc. 1982,
59, 678.
11. Rollas, S.; Karakus, S.; Durgan, B.B.; Kiraz, M.; Erdeniz, H.
Farmaco. 1996, 51, 811.
12. Mamolo, M.; Vio, L.; Banfi, E. Farmaco. 1996, 51, 71.
13. Desai, K.; Baxi, A.J. J. Indian Chem. Soc. 1992, 69, 212.
14. Mandour, A.H.; Fawzy, N.M.; El-Shihi, T.H.; El-Bazza, Z.E. Pak. J.
Sci. Ind. Res. 1995, 38, 402; Chem. Abstr. 127: 135773.
15. Kidwai, M.; Misra, P.; Kumar, R.; Saxena, R.K.; Gupta, R.;
Bradoo, S. Monatsh. Chem. 1998, 129, 961.
16. Mazzone, G.; Pignatello, R.; Mazzone, S.; Panico, A.; Pennisi, G.
Farmaco. 1993, 48, 1207.

SUBSTITUTED THIOUREAS AND PHASE TRANSFER CATALYSIS
1119
17. Chufan, E.E.; Pedregosa, J.C.; Badini, O.N.; Bruno-Blanch, L.
Farmaco. 1999, 54, 838.
18. Nomoto, Y.; Takai, H.; Hirata, T.; Teranishi, M.; Ohno, T.; Kubo, K.
Chem. Pharm. Bull. 1991, 39, 86.
19. Vio, L.; Mamolo, M.G.; Laneve, A. Farmaco. 1989, 44, 165.
20. Amir, M.; Oberoi, A.; Alam, S. Indian J. Chem. Sect. B 1999, 38, 237.
21. Nishino, C.; Sato, F.; Uetake, T.; Fukunish, H.; Kojima, N.
US5912258 1999; Chem. Abstr. 131: 31943.
22. Krutosikova, A.; Kovac, J.; Sykova, V. Collection Czecholov. Chem.
Commun. 1976, 41, 2577.
23. Wasfy, A.A.F.; Nassar, S.A.; Erissa, A.M.F. Indian J. Chem. Sect. B
1996, 35, 1218.
24. Chaturvedi, B.; Tiwari, N.; Nizamuddin. Indian J. Chem. Sect. B 1989,
28, 358.
Received in the USA March 29, 2001