Abstract
Novel catalytic synthesis of 6,7-dimethoxyisatin with the use of heteropolyacids (HPAs) as acid solid catalyst An efficient method for the preparation of 6,7-dimethoxyisatin and its derivatives was developed with good yield by using Preyssler-type heteropolyacid (HPA) as acid catalyst under green conditions. The comparison between Keggin type heteropolyacids, H3[PW12O40], H4[SiW12O40] and H4[SiMo12O40], H3[PMo12O40] and mineral acids with Preyssler's anion shows that the latter possess better catalytical activity than the other heteropolyacids and no degradation of the structure was observed.
Highlights
The problems associated with handling and disposal of inorganic acids, and their environmental and potential hazards have raised our interest in the development of alternative procedures using solid acid catalysts[1]
Synthesis of 2-nitro-3, 4-dimethoxy mandelonitrile (2) and its derivatives: 2-nitroveratraldehyde or other aldehydes (10 mmol) was added to the solution of NaHSO3 (11 mmol) and water (12 mL), the mixture was heated to 50°C, when 2-nitroveratraldehyde was dissolved; it was cooled to 0°C by ice bath, the solution of KCN (20 mmol) and water (5 mL) was added dropwise, and stirred for 2 hours at 0oC
We reported our researches about the synthesis of isatins compounds and using heteropolyacids catalysts and 2-nitro-3, 4-dimethoxy mandelonitrile 2 under the mild conditions (Scheme 1)
Summary
The problems associated with handling and disposal of inorganic acids, and their environmental and potential hazards have raised our interest in the development of alternative procedures using solid acid catalysts[1] Due to their super-acidic properties, heteropolyacids, HPAs, can be used in the reactions requiring electrophilic catalysis. Heteroplyacids (HPAs) have many advantages that make them environmentally attractive in the academic, industrial and economical signification These are useful acids and oxidation catalysts in various reactions since their catalytic features can be varied at a molecular level[2]. Isatins (1Hindole-2, 3-dione), synthetically versatile substrates, can be used for the synthesis of a large variety of heterocyclic compounds, such as indoles and quinolines, and as raw material for drug synthesis. They can be used for the synthesis of a large variety of heterocyclic compounds such as indoles and quinolines. These methods were both more complex and with poor yields
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