Nitroalkenes with enaminones

Heating of the dihydroisoquinoline 285 with the nitrostyrene 286 allowed practical preparation of the system 287 en route to the natural product lamellarin K <2004AGE866>. Reactions between nitroalkenes and enaminones have also been employed as the key step in a solid-phase approach to pyrrole-3-carboxamide derivatives (Equation 88) <1998TL8263>. 

The reaction of enaminones with nitroalkenes gives a pentalenone system via the Michael addition and aldol reaction (Eq. 4.66).85a Linear a-keto enamines react with nitroalkenes to afford [3 + 2] carbocyclized products.8515... 

The 13C-, 15N- and -NMR spectral data for a series of simple l-amino-2-nitroalkenes are collected in Table 30. The greater electron-withdrawing character of the nitro group as compared with carbonyl results in downfield shifts of the resonances of C(2) ( + 10 to +14 ppm), the enaminic nitrogen ( + 23.2 to + 27.4 ppm) and the olefinic protons [ + 0.8 to +1.0 ppm for H(l) +1.5 to = 1.8 ppm for H(2)] of 2-nitroenamines with respect to enaminones. This deshielding does not affect C(l), which has in fact a lower chemical shift ( — 5.5 to — 10.2 ppm) in 2-nitroenamines. The NMR spectra show that 2-nitroenamines with a primary or a secondary amino groups exist in solution as solvent-dependent equilibrium mixtures of E- and Z-isomers. The... 

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