Decahydroquinoline, hydrogenation

Cl9H23CI2N5O, 2- 3-[4-(m-Chlorophenyl)-1-piperazinyl]propyl -s-tri-azolo-[4,3-a]-pyridin-3(2H)-one hydrochloride, 45B, 279 Cl9H24CINO5 H2O, 1-(3,4,5-Trimethoxybenzyl)-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline hydrochloride hydrate, 45B, 279 C19H2 eClNO, 7-(cis-1-Buten-3-yny1)-8-hydroxy-2-(3,4-pentadienyl)-1 -azaspiro[5.5]undecane hydrochloride, 39B, 203 C19H28N4O7, 8a-t-Butyl-trans-decahydroquinoline picrate, 46B, 260 C19H28N4O7, 8 -t-Butyl-trans-decahydroquinoline hydrogen picrate, 45B, 280 46B, 260... 

To return to a more historical development the mercuric acetate oxidation of substituted piperidines (77) should be discussed next. This study established that the normal order of hydrogen removal from the aW-carbon is tertiary —C—H > secondary —C—H > primary —C—H, an observation mentioned earlier in this section. The effect of substitution variations in the piperidine series can be summarized as follow s l-mcthyl-2,6-dialkyl and 1-methyl-2,2,6-trialkyl piperidines, as model systems, are oxidized to the corresponding enamines the 1,2-dialkyl and l-methyl-2,5-dialkyl piperidines are oxidized preferentially at the tertiary a-carbon the 1-methyl-2,3-dialkyl piperidines gave not only the enamines formed by oxidation at the tertiary a-carbon but also hydroxylated enamines as found for 1-methyl-decahydroquinoline (48) (62) l-methyl-2,2,6,6-tctraalkyl piperidines and piperidine are resistant to oxidation by aqueous mercuric acetate and... 

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). 

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... 

Alkali metal in ammonia reductions of pyrrolobenzodiazepine-5,11-diones give trans-2-aminocyclohexanecarboxylic acid derivatives (e.g., 4) in enantiomerically pure form.2 3 A method for preparation of cis-2-aminocyclohexanecarboxylic acids related to 4 is based on the enantioselective hydrolysis of symmetrical diesters with pig liver esterase.4 cis-2-Aminocyclohexane derivatives have been used for syntheses of aminocyclitol antibiotics.4 5 6-Alkyl-cis-2-aminocyclohexanecarboxylic acids can be prepared by alkali metal in ammonia reduction of pyrrolobenzodiazepine-5,11-diones followed by olefin hydrogenation the cis-decahydroquinoline alkaloid (+)-pumiliotoxin C has been prepared by this methodology.2... 

Decahydroquinoline Alkaloids.—Full details of a synthesis of ( )-pumiliotoxin-C hydrochloride and of its X-ray diffraction analysis, described briefly earlier,have been published. Two new syntheses of the racemic free base (31) have been described the first is outlined in Scheme 7. The final hydrogenation afforded the desired base (31) as major product, a consequence of a high order of stereoselectivity in this step. The second approach (Schemes 8 and 9) uses 1,3-bistrimethylsilyloxy-1,3-dienes as intermediates. In both of the latter pathways the final product is the lactam (32), the conversion of which to ( )-pumiliotoxin-C has already been documented. ... 

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. 

Besides the main alkaloids, about 20 minor P. A with different side chains, 15 allopumiliotoxins (with an OH-group at C-7 of the indolizine system), and 10 ho-mopumiliotoxins (with a quinolizidine system instead of indolizidine as the skeleton) as well as about 25 decahydroquinolines have been found however, the exact structures of some of them are still unknown. The minor alkaloids differ from the P. in the side chains which may be hydrogenated, oxidized, methylated, or shortened P. A and B exhibit cardiotonic and myotonic activities and are thus of pharmaceutical interest. Furthermore they have an effect on sodium ion channels. Subcutaneous injections of 50 pg P. A or 20 pg P. B in mice are lethal. The decahydroquinolines on the other hand are less toxic (injection of 400 pg P. C causes death of mice) and influence nicotine receptors as well as sodium and potassium channels. 

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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