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Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic Chemistry
Volume 39, 2009 - Issue 6
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Original Articles

Room-Temperature Synthesis of Pyrazoles, Diazepines, β-Enaminones, and β-Enamino Esters Using Silica-Supported Sulfuric Acid as a Reusable Catalyst Under Solvent-Free Conditions

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Pages 947-957 | Received 06 Jul 2008, Published online: 25 Feb 2009
 

Abstract

Silica-supported sulfuric acid (H2SO4·SiO2) has been utilized as a heterogeneous recyclable catalyst for a highly efficient regio- and chemoselective condensation of hydrazines/hydrazides, diamines, and primary amines with various β-dicarbonyl compounds at room temperature to afford pyrazoles, diazepines, and β-enaminones/β-enamino esters under solvent-free conditions within 5–15 min.

Notes

a Reactions performed with 1.0 mmol of β-dicarbonyl compound, 1.1 mmol of hydrazine/hydrazide, and 20 mg of H2SO4·SiO2 mixed for 5–8 min under solvent-free condition, at room temperature.

b Isolated yields after column chromatography.

c Yields of reactions performed in 50°C.

a Reactions performed with 1.0 mmol of β-dicarbonyl compound, 1.1 mmol of diamine, and 20 mg of H2SO4·SiO2 mixed for 15 min under solvent-free conditions at room temperature.

b Isolated yields after column chromatography.

a Reactions performed with 1.0 mmol of β-dicarbonyl compound, 1.1 mmol of primary amines, and 20 mg of H2SO4·SiO2 mixed for 6–12 min under solvent-free conditions at room temperature.

b Isolated yields after column chromatography.

c Reactions performed with 2.0 mmol of β-dicarbonyl compound, 1.1 mmol of primary amines, and 20 mg of H2SO4·SiO2 mixed for 6–12 min under solvent-free conditions at room temperature.

a Reactions performed with 1.0 mmol of pentane-2,4-diketone, 1.1 mmol of aniline, and 20 mg of H2SO4·SiO2 mixed for 7 min under solvent-free condition at room temperature.

b Isolated yields after column chromatography.

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