400
V. Polshettiwar, R. S. Varma / Tetrahedron Letters 49 (2008) 397–400
yields within 1–2 min. The reaction of 1,2-diamino-
benzene with methylacetoacetate, however, failed to give
the desired product (entry 5), but after exposure to
microwave irradiation yielded imidazole derivative
References and notes
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1
(
not shown) exclusively; more investigations are cur-
rently in progress to explore the reaction.
In conclusion, we have developed a greener and efficient
approach for the synthesis of pyrazoles and diazepines,
which gets completed in 1–2 min at room temperature
and may provide a useful route for rapid drug discovery.
The use of polystyrene supported, relatively low toxic,
and inexpensive PSSA as a catalyst and the water as a
reaction medium are additional eco-friendly attributes
of this synthetic protocol.
2
002, 6, 52–98.
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. Penning, T. D.; Talley, J. J.; Bertenshaw, S. R.; Carter, J.
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4
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The 1,3-diketone (1 mmol) and hydrazines/hydrazides
6
(
0
1.1 mmol) were placed in a 10 mL glass tube. To this
.1 mL of 20% PSSA solution in water was added and
mixed for 1–2 min on touch mixer. The products were
then extracted in to ethyl acetate and washed with dilute
sodium bicarbonate solution. After drying the organic
layer over sodium sulfate and evaporation of the sol-
vent, the product was isolated by passing the crude reac-
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7
8
9
1
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4
2
3
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The experimental procedure described above was
followed using the following mole ratio; 1.0 equiv of
Kelsey, R. D. Org. Lett. 2005, 7, 713–716.
1
2
,3-diketone, 1.1 equiv of diamines, and 0.1 mL of
0% PSSA solution in water (Table 2).
1
0. (a) Li, C.-J.; Chen, L. Chem. Soc. Rev. 2006, 5, 68; (b)
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, 51–63; (b) Polshettiwar, V.; Varma, R. S. Curr. Opin.
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Drug Discov. Devel. 2007, 10, 723–737.
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Vivek Polshettiwar was supported, in part, by the Post-
graduate Research Program at the National Risk Man-
agement Research Laboratory administered by the Oak
Ridge Institute for Science and Education through an
interagency agreement between the US Department of
Energy and the US EPA.
1
7
420–7422; (b) Polshettiwar, V.; Varma, R. S. Tetrahedron
Lett. 2007, 48, 5649–5652; (c) Polshettiwar, V.; Varma, R.
S. Tetrahedron Lett. 2007, 48, 7343–7346; (d) Ju, Y.;
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1
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Supplementary data