Azirine/Oxindole ring enlargement via Amidinium intermediates
| Autor: | Heinz Heimgartner, Stefan Bienz, Maged K. G. Mekhael, Anthony Linden |
|---|---|
| Přispěvatelé: | University of Zurich, Heimgartner, Heinz |
| Jazyk: | angličtina |
| Rok vydání: | 2004 |
| Předmět: |
Azirine
10120 Department of Chemistry 1303 Biochemistry 1503 Catalysis Ring (chemistry) Medicinal chemistry Biochemistry Catalysis Inorganic Chemistry Hydrolysis chemistry.chemical_compound Pyridine 540 Chemistry Drug Discovery Oxindole Physical and Theoretical Chemistry Aqueous solution 1604 Inorganic Chemistry 3002 Drug Discovery Extraction (chemistry) Organic Chemistry General Medicine chemistry Yield (chemistry) 1606 Physical and Theoretical Chemistry 1605 Organic Chemistry |
| Popis: | A novel general method for the synthesis of oxindoles, namely the 'azirine/oxindole ring enlargement via amidinium-intermediates' has been established: the reaction of 2H-azirin-3-amines 1 with BF3.OEt2 in THF solution at -78° leads to 1,3,3-trialkyl-2-amino-3H-indolium tetrafluoroborates 14 in good yields (Scheme 5). Treatment of aqueous solutions of 14 at 0° with aqueous NaOH (30%) and extraction with CH2Cl2 gives oily substances that are either hydrates of 1,3,3-trialkyl-2-dihydroindol-2-imines 15 or the corresponding indolium hydroxides. These products are transformed to the corresponding 1,3,3-trialkyl-2,3-dihydroindol-2-ones 17 in modest yields upon refluxing in H2O/THF. Reaction of 14 with Ac2O in pyridine at ca. 23° for 16 h followed by aqueous workup and chromatographic separation leads to mixtures of N-(1,3,3-trialkyl-2,3-dihydro-indol-2-yliden)acetamides 16 and oxindoles 17 (Scheme 6). Hydrolysis of 16 with aqueous HCl under reflux for 1 - 2 h gives oxindoles 17 in a good yield. Several oxindoles, spiro-oxindoles, and 5-substituted oxindoles were synthesized by means of the reactions mentioned above. |
| Databáze: | OpenAIRE |
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