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Acylenamines

The term enaminones is used in this section to designate enamines having at C(2) a carbonyl function conjugated with the carbon-carbon double bond. The two main groups of these compounds, 2-acylenamines (enaminoketones) and 2-alkoxycarbonyle-namines (enaminoesters), are discussed in the following subsections. [Pg.325]

Jcc coupling constants over the formal C=C bond have been measured for a few 2-acylenamines9. The values found for 3-diethylaminoacrolein and for diethylaminovinyl methyl ketone (344) are 71.8 and 70.9 Hz, respectively, which are ca 8 Hz lower than the value observed in simple enamines (77-79 Hz)9 (see Section II.A). This is the result expected considering the more extended conjugation in 2-acylenamines (322a-c) and the decrease of the s character of the olefinic double bond. [Pg.339]

TABLE 24. 15N-NMR chemical shifts [<5ch3i5no2 (PPm)] and coupling constants J (Hz)a for 2-acylenamines... [Pg.348]

Recently, Minkin and coworkers31 have reported on thermal and photoinitiated E-Z isomerizations in a series of bicyclic N-monosubstituted 2-acylenamines (6). The E-Z equilibrium was found to be strongly dependent on the heteroatom X. While the indole derivative 6a exists only in the hydrogen-bonded E form both in solution and in the crystalline state, the benzofuran analogue 6b adopts the Z form in the crystal and in polar solvents. In chloroform and in hydrocarbon solvents, a slow transformation to the E form occurs, accelerated by heat and by catalytic amounts of acids and bases. The benzothiophene analogue 6c behaves similarly, and on irradiation a photostationary mixture of E and Z forms is established, which returns to the initial form in the dark. [Pg.411]

However, in 7V,A-disubstituted 2-acylenamines, suitable C2-substituents can also destabilize the E form sufficiently to make the observation of the Z form possible. Thus, barriers to rotation about the C=C bond of 11.2 and 13.8 kcal mol-1, respectively, have been reported for 7 and 832. The low barriers compared to those reported above may be ascribed to ground-state strain, but it is not completely excluded that the observed exchange is due to acetyl group rotation. [Pg.411]

Possible geometric forms of 2-acylenamines. For A-D, the symbols indicate, in this order, the conformation around C(l)—Q2) and the configuration around C(2)=C(3). For E-L, the symbols indicate, in this order, the conformation around C(l)—C(2), the configuration around C(2)=C(3),... [Pg.326]

Sterically unencumbered 2-acylenamines like lV,iV-dimethyIaminoacrolein (2a) have a strong predominance for the E configuration with respect to both the C =C and. [Pg.408]


See other pages where Acylenamines is mentioned: [Pg.279]    [Pg.325]    [Pg.326]    [Pg.327]    [Pg.347]    [Pg.347]    [Pg.353]    [Pg.405]    [Pg.406]    [Pg.406]    [Pg.408]    [Pg.408]    [Pg.415]    [Pg.279]    [Pg.325]    [Pg.327]    [Pg.347]    [Pg.347]    [Pg.352]    [Pg.353]    [Pg.406]    [Pg.415]   


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A-Acylenamines

N-Acylenamines

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