Microwave Promoted Synthesis of Spiro[indole-pyranobenzopyrans]
J. Chin. Chem. Soc., Vol. 50, No. 2, 2003 277
(
1) and malononitrile (0.01 mol) in absolute ethanol (15 mL)
containing piperidine (2-3 drops) as catalyst was refluxed for
-4 h. After being chilled overnight, the resulting solid was
filtered, washed with ether and recrystallized from ethanol.
fully acknowledged. One of us, (R.S.) is thankful to C.S.I.R.,
New Delhi for the award of S. R. F.
3
Received April 29, 2002.
(ii) Synthesis of spiro compound 5/6
A solution of 2 (0.01 mol) and 1-phenyl-2-thiohydan-
REFERENCES
tion (3)/4-hydroxy-2H-1-benzopyran-2-one (4) (0.01 mol) in
ethanol (50 mL) was treated with piperidine (2 drops) and
was stirred at room temperature for 4 h. After the removal of
ethanol to get colourless crystal, which were homogeneous
on TLC.
1
. Sallay, S. I. J. Am. Chem. Soc. 1967, 89, 6762.
. A Review on “Indoles with C-3 as spiro atom,” Joshi, K. C.;
Jain, R.; Chand, P. Heterocycles 1985, 23, 957 and refer-
ences cited therein.
2
3
. (a) Sehwartz, R. C.; Hirsch, C. F.; Sigmuna, J. M.; Peltibone,
D. J. US Pat. 1989, 4803217; Chem. Abstr. 1989, 111,
General Procedure under Microwave Irradiation
Spiro compound 5/6 have been synthesized in one step
without the isolation of intermediate (2) using microwave ir-
radiation by two different methods.
1
32572 h. (b) Okada, K.; Hashizume, K.; Tanino, H. Chem.
Pharm. Bull. 1989, 37, 791.
4. Murray, R. D. H.; Mendez, J.; Brown, S. S. The Natural
Coumarins; Wiley: New York, 1982; Murray, R. D. H. Prog.
Chem. Org. Nat. Prod. 1991, 58, 83.
(
a) A mixture of 1 (2 mmol) and malononitrile (2
mmol) in absolute ethanol (5-10 mL) in the absence/presence
of piperidine (1 drop) was irradiated for an appropriate time
5
. Feuer, G. Progress in Medicinal Chemistry; ed. G. P. Ellis
and G. B. West, North-Holland Publishing Co., New York,
(
Table 1) at 340/275 watts. As the reactants disappeared, 3/4
1
974.
was added, mixed thoroughly and again irradiated. The mix-
ture was then cooled and the product separated was filtered
and found to be of sufficient purity in most cases while in oth-
ers recrystallized from ethanol.
6
7
. Havera, H. J.; Strycker, W. G. US Pat. 1973, 3835151;
Chem. Abstr., 1973, 81, 152224.
. (a) Oussaid, A.; Pentek, E.; Loupy, A. New J. Chem. 1997,
2
1, 1339. (b) Gelco-Pujic, M.; Guibe-Jampel, E.; Loupy, A.;
Absence of catalyst simplifies the workup procedure as
the crystalline product of sufficient purity was separated di-
rectly, while the product obtained in the presence of piper-
idine was triturated with petroleum ether and recrystallized
from ethanol.
Trincone, A. J. Chem. Soc., Perkin Trans I 1997, 1001. (c) A
Review on “New Solvent free Organic Synthesis using Fo-
cussed Microwaves”, Loupy, A.; Petit, A.; Hamelin, J.;
Texier-Boullet, F.; Jacquault, P., Mathe, D. Synthesis 1998,
1213 & references cited therein. (d) Suarez, M.; Loupy, A.;
Salfran, E.; Moran, L.; Rolando, E. Heterocycles 1999, 51,
(
b) A mixture of 1 (2 mmole) and malononitrile (2
2
1.
mmol) adsorbed on neutral alumina/silica gel (2 g) with the
help of methanol was irradiated inside a microwave oven at
8
. (a) Dandia, A.; Taneja, H.; Gupta, R.; Paul, S. Synth.
Commun. 1999, 29, 2323. (b) Dandia, A.; Upreti, M.; Rani,
B.; Pant, U. C. J. Chem. Res. (S) 1998, 752; J. Chem. Res.
3
40 watts. As the reactants disappeared (TLC), 3/4 (2 mmol)
adsorbed on neutral alumina/silica gel was added to the reac-
tion mixture, mixed thoroughly and again irradiated for an
appropriate time (Table 1). Extraction with methanol and re-
moval of the solvent on a rotaevaporator afforded the pure
product.
(
M) 1998, 3348. (c) Dandia, A.; Saha, M.; Taneja, H. J. Fluo-
rine Chem. 1998, 90, 17. (d) Dandia, A.; Saha, M.; Rani, B.
J. Chem. Res. (S) 1998, 360; J. Chem. Res. (M) 1998, 1425.
(
e) Dandia, A.; Sachdeva, H.; Singh, R. J. Chem Res. (S)
2000, 272. (f) Dandia, A.; Sachdeva, H.; Singh, R. Synth.
Commun. 2000, 31(12), 87.
The identity of the product synthesized by various
1
methods was established by their mixed MP’s, IR and H
9. Loupy, A.; Pigeon, P.; Ramdani, M. Tetrahedron 1996, 52,
705. (b) Langa, F.; De La Cruz, P.; De La Hoz, A.;
Diaz-Ortiz, A.; Diez-Barra, E. Contemporary Org. Synth.
997, 373. (c) Brain, C. T.; Paul, J. M.; Loong, Y.; Oakley, P.
6
NMR.
1
J. Tetrahedron Lett. 1999, 40, 3275. (d) Hajipour, A. R.;
Mallakpour, S. E.; Afrousheh, A. Tetrahedron 1999, 55,
ACKNOWLEDGMENT
2
311. (e) Vega, J. A.; Vaquero, J. J.; Alvarez-Builla, J.;
Financial assistance from U.G.C., New Delhi is grate-
Ezquerra, J.; Hamdouchi, C. Tetrahedron 1999, 55, 2317.