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Quinoxaline 2 -ketones

Although 1- and/or 4-acylated hydroquinoxalines might not be considered as regular quinoxalone ketones, they are included here for pragmatic reasons. Examination of the NMR chemical shifts for H5 and H8 in l,4-diacyl-l,2,3,4-tetrahydroquinoxalines (197, R = Me, Et, Ph, etc.) indicated that the endo-exo conformation (shown) predominated in most such compounds at ambient temperatures. However, this was disturbed in l,4-dibenzoyl-6,7-dimethyl-l,2,3,4-tetra-hydroquinoxaline (198), which showed a predominance of the exo-exo conformation (shown) below the coalescence temperature.  [Pg.352]

The main preparative routes to quinoxaline ketones have been discussed earlier by primary synthesis (Chapter 1), by extranuclear acylation of alkylquinoxalines (Section 2.2.4), by oxidation of appropriate alkylquinoxalines (also Section 2.2.4), by displacement of a halogeno substituent (Section 3.2.7), by oxidation of... [Pg.352]

Note. Such derivatives of quinoxaline ketones are not encountered as often as those of quinoxalinecarbaldehydes, but a few examples can be given here. 6-Acetyl-2-phenylquinoxaline gave its oxime, 6-[l-(hydroxyimino)ethyl]-2-phe-nylquinoxaline (209) (H2NOH HCl, NaOH, EtOH, H2O, reflux, 2 h 75%). ... [Pg.354]

Also other examples.915,966 Oxidation to Quinoxaline Ketones... [Pg.217]

See other pages where Quinoxaline 2 -ketones is mentioned: [Pg.217]    [Pg.298]    [Pg.352]    [Pg.352]    [Pg.353]    [Pg.353]    [Pg.355]    [Pg.298]    [Pg.352]    [Pg.352]    [Pg.353]    [Pg.353]    [Pg.355]   
See also in sourсe #XX -- [ Pg.352 ]

See also in sourсe #XX -- [ Pg.352 ]



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