BAMBERGER Imidazole cleavage

SALLY - SCHOLL Benranthrene synthesis t5 BALSON Alkylation 15 BAMBERGER Imidazole cleavage 16 BAMBERGER Phenythydroxylamme rearrangement 17... 

Bamberger Imidazole Cleavage Shown by Benzimidazoles and Adenosines... 

In their efforts to reinvestigate a 1928 synthesis by van der Merwe histamine and / -anisaldehyde as starting materials, Stocker and Evans 1990 reported an application of the Bamberger imidazole cleavage in the general synthesis of compounds such as 13. They proved that 12 was actually the result of cyclization of the corresponding Schiflf s base rather than just the Schiff s base that van der Merwe had earlier suggested. ... 

Itaya et al have applied the Bamberger imidazole cleavage reaction and subsequent reclosure of l-alkyl-5-(alkylamino)imidazole-4-carbonitriles to transform imidazoles to their corresponding 2-oxo derivatives during their efforts to find an alternative entry into the synthesis of caissarone hydrochloride (26), a 3,6,9-trialkylpurine. 

Altman et al. have used the Bamberger imidazole cleavage reaction of substituted imidazoles in producing enantio-enriched vicinal di-acylamines. Specifically ring cleavage of 25 with (-)-menthyl chloroformate introduces chiral carbamate substituents on the double bond in menthyl carbamates 28 and 29. Hydrogenation of the hydrolyzed product 30 leads to preferential formation of vicinal diamide 32 over 31 in a diastereomeric ratio of 5 1. 

Altman s result shows that the Bamberger imidazole cleavage using asymmetric carbamates provided entry into vieinal diamines albeit with modest facial selectivity via hydrogenation. 

Cohen and co-workers have reported a facile synthesis of 2-(trifluoro-methyl)histamine and 2-(trifluoromethyl)-L-histidine using histamine and L-histidine as starting materials, repectively. The desire to use histamine and histidine was mainly due to ready availability, which would lead to rapid synthetic sequences and a direct entry into the fluorinated L-amino acid series. cw-l,2-Dibenzamido-l-alkenes (34) prepared by the Bamberger imidazole cleavage of corresponding imidazoles (33) were condensed with trifluoroacetic anhydride at reflux (40 °C) to yield 2-trifluoromethyl substituted imidazoles (35) in about 70% yield. 

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