Quinolines bond orders

Bond orders, charges on the atoms in 1 l//-pyrido[2,l-Z)]quinazolin-l 1-one and its protonated form were calculated by quantum chemical calculations by the semiempirical AMI method. According to the results, the equilibrium conformation of the ring in 1 l//-pyrido[2,l-Z)]quinazolin-l 1-one is planar, while l//-pyrimido[l,2-u]quinolin-1-one adopts a conformation close to a half-chair due to the unfavorable interactions between the oxygen atom of the carbonyl group and the ring C-10 atom in the pen-position (97MI22). 

The discussion of aromatic reactivity has proceeded in terms of molecular orbital theory. The valence-bond method has also been used to evaluate quantities which are parallel to those discussed above. The methods have in common the charge densities, and the free valency and bond order of molecular orbital theory have counterparts of similar but not identical significance in the valence-bond method. The latter has not been used widely in dealing with heterocyclic compounds, and so will not be much referred to here. In Table 3J are included data obtained by the valence-bond method for pyridine and quinoline. The use of molecular diagrams originated with studies in the valence-bond method fr,... 

QUINAPHOS ligands are usually synthesized in a one-pot-procedure from readily available 8-substituted quinolines [8] via nucleophilic addition of a lithium reagent [9] to the azomethinic double bond and direct quenching of the resulting 1,2-dihydroquinoline amide 1 with a phosphorochloridite derived from enantio-merically pure binaphthol (1) or from 3,3 -di-t-butyl-5,5 -dimethoxybiphenyl-2,2 -diol (m) [10] (Scheme 2.1.5.1, Method A). Alternatively, the anion 1 can be reacted with an excess (in order to avoid multiple substitution) of phosphorous trichloride to obtain the corresponding phosphorous dichloridite 2, which can be isolated (Scheme 2.1.5.1, Method B). In a second step, 2 is converted into 4 by reaction with the desired diol in the presence of triethylamine. 

Polar solvents and in particular hydrogen bonds are able to stabilize polar molecules. This is also true for the excited states of a molecule that may have quite different polarities, and solvent variation may possibly change the energy order of the excited states as well as transition moments. (Cf. Section 2.7.2.) As an example we recall quinoline, whose solvent-dependent fluorescence quantum yield has been discussed in Section 5.3.2. 

Similar metal-phosphine derivatives previously shown to be good catalysts for C=C and C=O bond reduction, were reported by Sanchez-Delgado and Gonzalez [78] to be efficient also for quinoline hydrogenation at 150° C and 30 atm Hj. The order of activity observed was ... 

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