Quinoline decahydroquinoline

Reduction. Quinoline may be reduced rather selectively, depending on the reaction conditions. Raney nickel at 70—100°C and 6—7 MPa (60—70 atm) results in a 70% yield of 1,2,3,4-tetrahydroquinoline (32). Temperatures of 210—270°C produce only a slightly lower yield of decahydroquinoline [2051-28-7]. Catalytic reduction with platinum oxide in strongly acidic solution at ambient temperature and moderate pressure also gives a 70% yield of 5,6,7,8-tetrahydroquinoline [10500-57-9] (33). Further reduction of this material with sodium—ethanol produces 90% of /ra/ j -decahydroquinoline [767-92-0] (34). Reductions of the quinoline heterocycHc ring accompanied by alkylation have been reported (35). Yields vary widely sodium borohydride—acetic acid gives 17% of l,2,3,4-tetrahydro-l-(trifluoromethyl)quinoline [57928-03-7] and 79% of 1,2,3,4-tetrahydro-l-isopropylquinoline [21863-25-2]. This latter compound is obtained in the presence of acetone the use of cyanoborohydride reduces the pyridine ring without alkylation. 

Each of the three decahydroquinoline sulfonates shown below gives a different product composition on solvolysis. One gives 9-methylamino-E-non-5-enal, one gives 9-methylamino-Z-non-5-enal, and one gives a mixture of the two quinoline derivatives 14-D and 14-E. Deduce which compound gives rise to which product. Explain your reasoning. 

The supported complex [Rh(cod)(POLYDIPHOS)]PF6, obtained by stirring a CH2C12 solution of [RhCl(cod)]2 and Bu4NPF6 in the presence of a diphenyl-phosphinopropane-like ligand tethered to a cross-linked styrene/divinylbenzene matrix (POLYDIPHOS), forms an effective catalyst for the hydrogenation of quinoline (Fig. 16.8) [84]. Under relatively mild experimental conditions (80 °C, 30 bar H2), quinoline was mainly converted to THQ, though appreciable formation of both 5,6,7,8-THQ and decahydroquinoline also occurred (Scheme 16.20). 

Practically pure cw-decahydroquinoline (43) (containing 3% trans isomer) can be obtained by prolonged hydrogenation of quinoline in concentrated hydrochloric acid over platinum black (72JCS(P2)615). Hydrogenation over platinum in aqueous acetic acid gives a preponderance (80%) of the frans-decahydroquinoline (44 Scheme 31). 

Quinoline may be reduced rather selectively, depending on the reaction conditions. Catalytic reduction with platinum oxide in strongly acidic solution at ambient temperature and moderate pressure gives a 70% yield of 5,6,7,8-tetrahydroquinoline. Further reduction of this material with sodium-ethanol produces 90% of fratrr-decahydroquinoline. 

As illustrated by Figure 27.6(d), the denitrogenation of quinoline is found to be a more difficult reaction. In the absence of sulfur, the oxynitride and the oxycarbide exhibit little activity for denitrogenation of quinoline in the absence of sulfur, while the hematite does not show any activity whatsoever (not shown). At the reaction conditions studied, the quinoline rapidly converted into tetrahydroquinoline, as evidenced by the high conversion rate indicated in Table 27.3, which reacted more slowly to form propylaniline, tetrahydroquinoline and decahydroquinoline. Only a small fraction of propylbenzene is detected as a nitrogen free product, accounting for less than 1% HDN. Sulfur addition as DMDS results in a moderate increase in HDN activity (4% HDN) for both Mo2NaO>, and... 

HDN of Quinoline. Satterfield et al.(8) proposed that there are two pathways for the HDN of the coal liquid model compound quinoline using a NiHMocatalyst. One pathway involves the successive formation from quinoline of 1,2,3,4-tetrahydroquino-line, o-propylaniline and then ammonia plus n-propylbenzene. A second pathway involves the successive formation of 5,6,7,8-tetrahydroquinoline, decahydroquinoline, propylcyclohexylamine... 

Table I gives the results from the experiments with [M(PC)] supported on Si02 The conversion of quinoline is almost exclusively to 1,2,3,4-tetrahydroquinoline with only traces of other products (<1%). No propylaniline, propylbenzene, propyl-cyclohexane, 5,6,7,8-tetrahydroquinoline or decahydroquinoline were noted. No change is noted in the conversions when the SiC>2 is activated in vacuo at 400°C prior to supporting the complex. When the hydrogenations are run at 200°C only low conversions are...

Over copper-chromium oxide, quinoline is quantitatively hydrogenated to tetrahydroquinoline, and further hydrogenation to decahydroquinoline does not proceed even at 190°C and 10-15 MPa H2 (eq. 12.45).71 Over reduced copper catalyst quinoline was hydrogenated to tetrahydroquinoline at 130°C and 14 MPa H2. Hydrogenation of the tetrahydroquinoline produced took place only very slowly at 260°C and 16 MPa H2 to give /ra/i.v-dccahydroqu incline.20... 

Over ruthenium dioxide quinoline was hydrogenated to tetrahydroquinoline in 97.5% yield at 80°C and 8.2 MPa H2 and to decahydroquinoline in 98% yield at 120°C and 9.3 MPa H2.3 Quinoline was also hydrogenated to tetrahydroquinoline over colloidal platinum in neutral solution or as the hydrochloride over platinum oxide in absolute ethanol.30 Hydrogenation to decahydroquinoline was performed with platinum black (Willstatter) or colloidal platinum (Skita) in acetic acid.73,74 Hiickel and Stepf hydrogenated quinoline under almost the same conditions as used by Skita and Meyer, and obtained the decahydroquinoline consisting of approximately 80% of trans and 20% of cis isomers (eq. 12.46). 

Formation of the cis isomer increased to 65% when quinoline was hydrogenated in acetic acid added by a large quantity of hydrochloric acid.72 Booth and Bostock obtained practically pure cw-decahydroquinoline by hydrogenation of quinoline in concentrated hydrochloric acid over platinum black (eq. 12.47).75 Vierhapper and Eliel showed that the hydrogenation in the strongly acidic medium proceeds mostly via 5,6,7,8-tetrahydroquinoline as intermediate, which probably is related to the high stereoselectivity in the formation of the cis isomer.37... 

Selective hydrogenation of quinolines and isoquinolines. Catalytic hydrogenation of quinolines and isoquinolines usually occurs preferentially in the pyridine ring. However, if the hydrogenation is conducted in trifluoroacetic acid, the reverse situation obtains and the benzene ring is reduced more rapidly. The same result can be obtained with mineral acids, but such hydrogenations are much slower. Both 2- and 4-phenylpyiidine can also be reduced preferentially in the benzene ring. Platinum oxide or palladium or rhodium catalysts can be used. Further reduction of 5,6,7,8-tetrahydroquinolines with sodium and ethanol provides a convenient route to rrans-decahydroquinolines. 

In the quinoline ring system, the heterocyclic ring is more easily reduced than the benzene ring, forming tetrahydro-compounds or even decahydroquinoline derivatives under hydrogenation conditions. Quinolines have also been reduced to 1,2,3,4-tetrahydroquinolines by zinc borohydride and dimethylaniline under sonication conditions or with indium metal in... 

The Langmuir-Hinshelwood model has been applied in the study of the kinetics of the HDN of o-propylaniline, decahydroquinoline, and quinoline over NiMo(P)/Al203 catalysts by Jian and Prins [5-7]. It has been reported that direct C(5p )-N bond cleavage takes place on a different catalytic site than hydrogenation reactions [8]. Nevertheless, Jian and Prins assumed that o-propylaniline has the same adsorption constant on the catalytic sites used in hydrogenation and in C(sp yN bond cleavage [5]. The fact that changes in the initial partial pressure of o-toluidine do not affect the ratio of the product of path 1 to the product... 

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