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Bortrifluorid-katalysierte Umsetzung yon 3-Amino-2H-azirinen mit Amiden: Bildung von 4,4-disubstituierten 4H-Imidazolen


Arnhold, Franziska; Chaloupka, Stanislav; Linden, Anthony; Heimgartner, Heinz (1995). Bortrifluorid-katalysierte Umsetzung yon 3-Amino-2H-azirinen mit Amiden: Bildung von 4,4-disubstituierten 4H-Imidazolen. Helvetica Chimica Acta, 78:899-909.

Abstract

Boron Trifluoride Catalyzed Reaction of 3-Amino-2H-azirines and Amides: Formation of 4,4-Disubstituted 4H-Imidazoles Reaction of trifluoroacetamide and 3-amino-2H-azirines 1 in refluxing MeCN affords 4-amino-2-(trifluoromethyl)-4H-imidazoles 5 in fair yields (Scheme 3). Less acidic amides do not react with 1 under similar conditions. Therefore, a procedure involving BF3-catalysis has been elaborated: the aminoazirine 1 in CH2CI2 at -78° is treated with BF3.Et2O and then with a solution of the sodium salt of an amide in THF, prepared by addition of sodium hexamethyldisilazane at -78°. The 4H-imidazoles of type 5 are formed in ca. 50% yield (Scheme 4). Reaction mechanisms for this ring enlargement of 1 are proposed in Schemes 5 and 6.

Abstract

Boron Trifluoride Catalyzed Reaction of 3-Amino-2H-azirines and Amides: Formation of 4,4-Disubstituted 4H-Imidazoles Reaction of trifluoroacetamide and 3-amino-2H-azirines 1 in refluxing MeCN affords 4-amino-2-(trifluoromethyl)-4H-imidazoles 5 in fair yields (Scheme 3). Less acidic amides do not react with 1 under similar conditions. Therefore, a procedure involving BF3-catalysis has been elaborated: the aminoazirine 1 in CH2CI2 at -78° is treated with BF3.Et2O and then with a solution of the sodium salt of an amide in THF, prepared by addition of sodium hexamethyldisilazane at -78°. The 4H-imidazoles of type 5 are formed in ca. 50% yield (Scheme 4). Reaction mechanisms for this ring enlargement of 1 are proposed in Schemes 5 and 6.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:German
Date:1995
Deposited On:04 Dec 2013 13:29
Last Modified:05 Apr 2016 17:12
Publisher:Wiley-Blackwell
ISSN:0018-019X
Funders:Schweizerischer Nationalfonds zur Förderung der wissenschaftlichen Forschung, f. Hoffmann-La Roche AG, Basel

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