The n.m.r. spectra of the four geometrical isomers of β-aminoenones, trans-s-trans, trans-s-cis, cis-s-trans, and cis-s-cis, are discussed. It was found that the chemical shift of the α-proton of β-aminoenones depends on both anisotropic effects and the electron density: δ=δ0–Δδstruc=ΔδAr+K(q–q0). Thus the conformation of non-rigid β-aminoenones can be determined from the observed and the calculated
In contrast with their oxo-analogues, thioenamides undergo photochemical cyclization to yield isoquinolinethione derivatives which are easily converted into isoquinolones and tetrahydroisoquinolines by treatment with benzeneseleninic anhydride and EtO3BF4–NaBH4, respectively.
3-Methyl-5-nitropyrimidin-4(3H)-one reacted with enaminones to cause the ring transformation leading to functionalized 4-aminopyridines. Various kinds of amino groups can be introduced at the 4-position by modifying the enaminones. The modification of its vicinal positions was also possible. In addition, a bicyclic pyridine could be synthesized by making use of the vicinal functionality of a 4-aminopyridine-3-carboxylic acid.