Quinoline ring according

Molecular modeling studies performed by Schaus [30] to rationalize the observed sense of stereoselectivity revealed that the nucleophile (i.e., the conjugate base of the malonate) is hydrogen-bonded to both the thiourea moiety and the protonated quinuclidine catalyst and that one face of the nucleophile is blocked by the quinoline ring. Accordingly, the Re-face attack of the nucleophile on the Z-aldimine was proposed to produce the observed (S)-Mannich product (Figure 8.5). 

According to the work of Greenhill and Mohamed dimedone enamine is attacked by methyl vinyl ketone in propionic acid at the / -position leading to quinoline ring closure. 

Thus, the main question of the mechanism of reaction consists of the mode of conformation of the alkaloid modifier on the surface of the catalyst. As mentioned above, there are two mechanistic concepts, which can be divided into path 1 and path II. According to path I, alkaloid modifier (e g. Cnd) interacts with EtPy adsorbed on the surface of Pt by means of adsorption of the quinoline ring in the open conformation according to the Scheme 5.28. as a (Augustine et al. ), 6 (Baiker, Blaser et al. ), c (Blaser et al. ) or (Simons et al. ). According to path II, intermediate... 

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). 

This chapter includes the recent various aspects of four and five membered heterocyclo-quinolines containing one nitrogen atom at the ring junction. They were subdivided according to the number of heteroatoms in the heterocyclic rings. The literature indicates that many of these heterocycles are of potential therapeutic value which leads to intensive research in the topic. On the other hand, there are various classes of heterocycles that fit under this heading but unreported yet. Consequently, efforts towards the synthesis of such unreported classes can be fruitful area of research. 

The dipole moments of some pseudoazulenes were determined by dielectric measurements. They are listed in Table II. The high values obtained (for comparison 6,6-dihydroindeno[2,1-b]quinoline has a dipole moment of 1.66 D whereas the corresponding 6-oxo compound has a value of approximately 1.6 D) are in accordance with quantum chemical calculations (see Section IV,B). The relatively high values of the dipole moments of unsubstituted pseudoazulenes and their derivatives show that some of the polar structures contribute to the resonance hybrid (Eq. 7). But in all cases the ring heteroatoms are localized at the positive end of the dipole. 

Simple tertiary enaminones derived from acetylacetone and benzoylacetone react with acryloyl chloride to yield carbocyclic derivatives. The reaction proceeds via an initial Michael addition of the enaminone / -carbon to the enone107 (equation 76). Analogous behavior of cyclic enaminones leads, according to ring size, to tetrahydroindole, quinoline and benzazepine derivatives108 (equation 77). 

Yamashkin, S. A., Yudin, L. G., Kost, A. N. Pyridine ring closure in synthesis of quinolines according to Combes (review). Khim. Geterotsikl. Soedin. 1992,1011-1024. 

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