Friedel-Crafts-Acylierungen aliphatischer Verbindungen. VII. Friedel-Crafts-Acylierungen von Carbonsäurechloriden mit Maleinsäureanhydrid - ein neuartiger Zugang zu Tetronsäuren
✍ Scribed by Prof. Dr. sc. nat. H. Schick; Dr. E. Gründemann; Dr. D. Ballschuh
- Publisher
- John Wiley and Sons
- Year
- 1980
- Tongue
- English
- Weight
- 607 KB
- Volume
- 322
- Category
- Article
- ISSN
- 1615-4150
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✦ Synopsis
Friedel‐Crafts‐Acylations of Aliphatic Compounds. VII. Friedel‐Crafts‐Acylations of Carboxylic Acid Chlorides with Maleic Acid Anhydride — a New Access to Tetronic Acids
Reaction of succinic acid with propionyl chloride under Friedel‐Crafts‐reaction conditions yields 2‐methyl‐cyclopentan‐1,3‐dione. The related reaction of maleic acid anhydride with propionyl chloride does not yield 2‐methyl‐cyclopent‐4‐en‐1,3‐dione 7, but a E/Z‐mixture of the lactones 5 and 8. By treating with hydrogen chloride in methanol or with thionylchloride in methanol the lactone mixture is converted to dimethyl (2Z, 4E)‐3‐hydroxy‐2‐methyl‐hexa‐2,4‐diendioate 10. By reaction with excessive sodium hydroxide the mixture of lactones is transformed into tetronic acid 11. Structure determinations are based on u.v.‐, i.r.‐, m.s.‐ and n.m.r.‐spectroscopy and on further chemical transformations. This tetronic acid synthesis represents an intramolecular addition of a carboxylate anion to an α, β‐unsaturated carbonyl compound.