4-Amino-1,5-dihydro-2H-pyrrol-2-one aus Bortrifluorid-katalysierten Umsetzungen von 3-Amino-2H-azirinen mit Carbonsäure-Derivaten

✍ Scribed by Martin Hugener; Heinz Heimgartner

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: German
• Weight: 589 KB
• Volume: 78
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19950780608

✦ Synopsis

4‐Amino‐1,5‐dihydro‐2__H__‐pyrrol‐2‐ones from Boron Trifluoride Catalyzed Reactions of 3‐Amino‐2__H__‐azirines with Carboxylic Acid Derivatives

Reaction of 3‐amino‐2__H__‐azirines 1 with ethyl 2‐nitroacetate (6a) in refluxing MeCN affords 4‐amino‐1,5‐dihydro‐2__H__‐pyrrol‐2‐ones 7 and 3,6‐diamino‐2,5‐dihydropyrazines 8, the dimerization product of 1 (Scheme 2). Thus, 6a reacts with 1 as a CH‐acidic compound by CC bond formation via C‐nucleophilic attack of deprotonated 6a onto the amidinium‐C‐atom of protonated 1 (Scheme 5). The scope of this reaction seems to be rather limited as 1 and 2‐substituted 2‐nitroacetates do not give any products besides the azirine dimer 8 (see Table 1). Sodium enolates of carboxylic esters and carboxamides 11 react with 1 under BF~3~ catalysis to give 4‐amino‐1,5‐dihydro‐2__H__‐pyrrol‐2‐ones 12 in 50–80% yield (Scheme 3, Table 2). In an analogous reaction, 3‐amino‐2__H__‐pyrrole 13 is formed from 1c and the Li‐enolate of acetophenone (Scheme 4). A reaction mechanism for the ring enlargement of 1 involving BF~3~ catalysis is proposed in Scheme 6.