Estudo da reatividade de alfa-enaminecetonas com nucleofilos capazes de formar compostos heterociclicos

AUTOR(ES)
DATA DE PUBLICAÇÃO

1989

RESUMO

The reactions of 4-(methy1-amine)-3-penteno-2- one with the corresponding diazocetone (RCOCN2R) yielded the a- acyl-enaminoketones (RR) CHCO(CH3CO)C=C(CH3)NHCH3 through the eletrofilic attack of the cetene on the a-carbon of the enaminones, These a-acyl-enaminoketones were reacted with hydrazine to obtain substituted pyrazoles with the objective of determining which of the carbonyls would be preferencely attacked by the nucleophile. The quantity of nucleophile added was varied in the proportion of 1 a-acyl-enaminoketone to 2 nucleophile and 1 a-acyl-enaminoketone to 4 nucleophile. The reactions of a-acyl-enaminoketones with hydrazine hydrate yielded as the major product the pyrazoles in which the carbonyl bonded to the (RRCH) group reacted preferencely. The reactions of a - acyl-enaminoketones with phenylhidrazine, in the proportion 1:4. yielded the pyrazoles in which the carbonyl bonded to the CH3 group reacted preferencely and yielded also the deacetylated pyrazoles 5-(1-Pheny1-ethyl)-3- methyl-1-phenyl-pyrazole 23 and 5-(1-methyl-ethyl)-3-methyl-1- phenyl-pyrazole 25. The same reaction to 14 (R=Ph e R=CH3) and (R=R=CH3) in the proportion of 1:2, yielded only compounds 23 and 25. When R=R=Ph, 12, the loss of the (Ph)2CHCO group is observed. Thus 1,1-dyphenyl-N-methyl acetamide and the 3,5-dimethyl-1-phenyl-pyrazole are formed. The reactions of the a-acyl-enaminoketones with p-nitrophenylhy- drazine yielded only the deacetylated pyrazoles. When R=R=Ph, 12, 3,5-dimethyl-1-p-nitro-phenyl-pyrazole and 1,1-dyphenyl-N-methyl acetamide are formed. We attribute the difference obtained in the results to the fact that the second nitrogen of phenylhydrazine and p-nitro-phenylhydrazine are less nucleophylic than in hydrazine hydrate.

ASSUNTO(S)

compostos heterociclicos

ACESSO AO ARTIGO

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