72600-16-9Relevant academic research and scientific papers
Enols of 2-nitro- and related 2-substituted malonamides
Basheer, Ahmad,Mishima, Masaaki,Rappoport, Zvi
, p. 255 - 265 (2010)
The structures of 2-substituted malonamides, YCH(CONR1R 2)CONR3R4 (Y=Br, SO2Me, CONH 2, COMe, and NO2) were investigated. When Y=Br, R 1R2=R3R4=HEt; Y=SO2Me, R1-R4=H and for Y=CONH2 or CONHPh, R 1-R4=Me, the structure in solution is that of the amide tautomer. X-ray crystallography shows solid-state amide structures for Y=SO 2Me or CONH2, R1-R4=H. Nitromalonamide displays an enol structure in the solid state with a strong hydrogen bond (O. . .O distance=2.3730 A at 100 K) and d(OH) 6≠d(O. . .H). An apparently symmetric enol was observed in solution, even in appreciable percentages in highly polar solvents such as DMSO-d6, but Kenol values decrease on increasing the solvent polarity. The N,N′-dimethyl derivative is less enolic. Acetylmalonamides display a mixture of enol on the acetyl group and amide in non-polar solvents, and only the amide in DMSO-d6. DFT calculations gave the following order of pKenol values for Y: H > CONH 2 > COMe ≥ COMe (on acetyl) ≥ MeSO2>CN> NO2 in the gas phase, CHCl3, and DMSO. The enol on the C=O group is preferred to the aci-nitro compound, and theN-O-H. . .O=C is less favored than the C=O-H. . .O=C hydrogen bond. Copyright
