Estudo da reatividade de a-acil-enaminocetonas com nucleofilos capazes de formar compostos heterociclicos parte II (volume I)

AUTOR(ES)
DATA DE PUBLICAÇÃO

1994

RESUMO

The reactions of 4-(methylamine)-3-penteno-2-one with several diazoketone (RCOCN2R) yielded the a-acyl-enaminoketones ( (RRCHCO (CH3CO) C=C(CH3)NHCH3 (134, R=R=Ph; 135 R=CH3 and R=Ph e 136 R=R=CH3), in good yielded. AM1 calculations show that the COCH3 group is in the plane of the molecule and thus conjugated with the double bond, while the (R=RCH)CO group remains perpendicular to the plane of the molecule. Reactions of the a-acyl-enaminoketones 134, 135 and 136 with hydrazine in five different solvents were accomplished with the goal of obtaining substituted pyrazoles and determining which of the carbonyls would be preferentially attached by the nucleophile. These reactions were accom- panied by gas-chromatography/ mass spectrometry (GC/MS). The results show formation the pyrazoles 146 by nucleophylic attack of the other carbonyl group. Besides these pyrazoles, the deacetylated pyrazoles 148 formed by the loss of CH3CO group and the pyrazoles formed by the loss of COCHRR group were also obtained. Very low yields of the 148 and 149 regioisomers of the pyrazoles 148 and 149 were obtained. The nucleo- phylic attack of the methylamine on the carbonyl bonded to the COCHCRR group was also detected. The results obtained in the reactions of the compounds 134, 135 and 136 with the hydrazines using five different solvents were complex. Because of this, chemometrics was used to help understand the role of the solvent and the carbonyl group reactivities on the product formation. Reactions of the a-acyl-enaminoketone 138 [ (PhCO) (CH3CO)C=C(CH3)NHCH3 ] with the hydrazine yielded analogous com - pounds. The unexpected formation of pyrazole 162 were detected when methanol and N,N-dimethylformamide were used as a solvent.

ASSUNTO(S)

compostos heterociclicos - reatividade

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