Circular dichroism of heterocyclohexan-4-onic systems

Photophysical properties of .beta.-amino ketones. Investigation of tropinone, N-methyl-4-piperidone, and 1-diethylamino-3-butanone

“…The uv spectrum of 3 is also characterized by a discernible shoulder at 290 nm (see Table I). Similarly, an inflection at 290 nm in addition to a -coupled transition at 243 nm (1366 M-1 cm'1) is also found in the spectrum of 10.6f As in 3, the band at 243 nm in 10 is not observed in model compounds, 1-azaadamantane (12), (Xmax 211 nm (1829 Mcm-1)) and 9 (Xmax 290 nm (19 M-1 cm-1)). The 290-nm shoulder in 10 was attributed to a "local" ir* n transition because it has the same energy as the ketone absorption in the model compound 9.6f It was suggested that the energy of the ir* «-n transition need not be affected by coupling with the nitrogen lone pair if the interaction is with the highest occupied orbital of the carbonyl group.6f The same rationalization can be used to explain the identical shoulder in the spectrum of 3 since it appears in the region of the carbonyl * <n transition of structurally similar bicyclic ketones 9 (Xmax 290 nm (18 M-1 cm-1))5 and norcamphor (Xmax 294 nm (22 M-1 cm-1)).5 An alternative and/or additional explanation for the 290-nm shoulder in the uv spectrum of 3 is that it is an absorption by the tropinone conformer 13 in which the A-methyl group is 0.88 " These are convenient reference wavelengths and do not correspond to absorption maxima.…”

Effect of Through‐Bond Interaction on Conformation and Structure in Rod‐Shaped Donor–Acceptor Systems. Part 2.

“…Sect. 2.1) is nicely reflected in an increase of the torsion angles H eq ÀC(3)ÀC(4)ÀC (9) and H eq ÀC(5)ÀC(4)ÀC (9) and a decrease of the torsion angles C(2)ÀC(3)ÀC(4)ÀC(5) and C(6)ÀC(5)ÀC(4)ÀC(3) compared to the other structures.…”

“…Two types of distortions from the ideal planar geometry can occur: twisting around the C(4)ÀC (9) bond and pyramidalization at C(4). For example, 4T2 and 2T3 show slight twisting around the C(4)ÀC(9) bond, which may be attributed to crystal-packing effects.…”

“…In this axial structure 1P2, the piperidine ring central CÀC bond was significantly elongated compared to the equatorial nPm derivatives. It was also observed that TBI is influencing the pyramidalization at C(4) of piperidine, in such a way that a strong interaction is directing the ethylene C-atom C (9) in the axial direction.…”

Development of a Crystallization-Induced Diastereomer Transformation of Oxime Isomers for the Asymmetric Synthesis of (1S,6R)-3,9-Diazabicyclo[4.2.1]nonane

“…The first step is a facile synthesis of nortropinone derivative 12 by utilizing a classic Robinson–Schöpf synthesis . Previous methods utilizing the Robinson-Schöpf method reported 4% yield after purification; alternatively, a 70% yield was obtained by utilizing a double aza -Michael addition of 17 to cyclohepta-2,6-dienone . We adapted the Robinson–Schöpf method by employing a buffer solution to achieve the optimum pH for this reaction and were able to obtain 12 in 73% isolated yield on a 50 g scale from 16 without the need for column chromatography purification, as the product is simply filtered at the end of the reaction and washed with water.…”