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DOI: 10.1055/s-2007-984878
Solvent-Free Basic or KF/Alumina-Assisted Dehydrogenation of Hydrazo Compounds
Publication History
Publication Date:
12 July 2007 (online)
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Abstract
A reduction of organic solvents in the organic chemical industry is of serious importance for sustainable chemistry. With this viewpoint, we successfully established the useful dehydrogenation of hydrazo compounds using basic alumina or KF/alumina under solvent-free conditions to afford azo compounds in good to excellent yields.
Key words
solvent-free - alumina - dehydrogenation - hydrazo compounds - azo compounds
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References and Notes
Basic alumina (lot 20), purchased from ICN, and KF/alumina (batch 16727CO), purchased from Aldrich, were used without further treatment.
20
Azo Compounds - Typical Procedure
Hydrazobenzene (1a, 1 mmol) was measured into a 100 mL flask containing KF/alumina (0.5 g). The reaction mixture was stirred at 80 °C for 30 min with blowing air under ambient pressure to obtain a red solid. Then, Et2O was added to the resulting mixture and filtered on a Büchner funnel to remove the alumina. The alumina was washed with Et2O and the combined filtrate was concentrated in vacuo. After purification by flash chromatography on silica gel eluting with EtOAc-hexane, azobenzene (2a) was obtained in a yield of 85%.
The reaction was also performed with 1a (10 mmol) and KF/alumina (5 g) following the same procedure except the reaction time. After a heating time of 45 min, 2a was obtained in a yield of 91% by passing through column of silica gel.