Chromium oxide-quinoline

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... 

The product is the isomer with the two phenyl groups cis to each other, since decarboxylation with quinoline-copper chromium oxide at 210-220° yields cis-stilbene. 

Copper chromite and copper-chromium oxide are effective catalysts for the decarboxylation of acids in quinoline solution. An example is the decarboxylation of cis-a-phenylcinnamic acid in refluxing quinoline to c/r-stilbene the two catalysts cited... 

This complex, formerly called pyridine perchromate and now finding application as a powerful and selective oxidant, is violently explosive when dry [1], Use while moist on the day of preparation and destroy any surplus with dilute alkali [2], Preparation and use of the reagent have been detailed further [3], The analogous complexes with aniline, piperidine and quinoline may be similarly hazardous [4], The damage caused by a 1 g sample of the pyridine complex exploding during desiccation on a warm day was extensive. Desiccation of the aniline complex had to be at ice temperature to avoid violent explosion [4]. Pyridinium chlorochromate is commercially available as a safer alternative oxidant of alcohols to aldehydes [5], See Chromium trioxide Pyridine Dipyridinium dichromate See Other AMMINECHROMIUM PEROXOCOMPLEXES... 

Benzo[g]quinolines, e.g. (40), and benzo[g]isoquinolines are oxidized to the corresponding azaanthraquinones using, for example, chromium trioxide in acetic acid (Scheme 28) (79KGS517). 

The classic SsAi substitution of activated aryl halides by protected cyanohydrin anions provides substituted benzophenones. Another procedure for the arylation of protected cyanohydrin anions involves the use of aromatic substrates activated as their rr-chromium tricarbonyl complexes. - Addition of the anion of (32) to the 1,3-dimethoxybenzene complex, for example, leads principally to the meta-suh-stituted isomer (33 equation 20). Preferential meta regioselectivity is also noted with other -rr-chromium tricarbonyl complexes of arenes. Other arylations of cyanohydrin anions include interesting but synthetically limited additions at the a-position of quinoline N-oxides. In a similar manner, cyanohydrin carbonates of aromatic aldehydes react with A -oxides of quinoline and isoquinoline. ... 

New reactions of isoquinoline derivatives include the following 3,4-di-hydroisoquinoline N-oxide with 2-acetylcycloalkane-l,3-diones, Reissert compounds with stilbene and tolan derivatives, isoquinoline with pyrrole derivatives and with 2-methylfuran " (both in the presence of benzyl chloride), and the chromium trioxide oxidation of the benzo[a]quinolizidine (49) to give (50). Compound (49) was prepared by the condensation of 3,4-dihydroiso-quinoline with the 5-lactone (51). Further examples of a classical benzo[a]-... 

The reaction of hexafluorobenzene with potassium p-cresoxide (4 molar equivalents) in dimethylformamide yields 1,4-bis-p-cresoxytetrafluoro-benzene (54%) oxidation of this with chromium trioxide gives the diacid (69) (83%), also obtainable from hexafluorobenzene and the dipotassium salt ofp-hydroxybenzolc acid (67%). A number of conventional derivatives of the diacid (69) are described, and its orientation is established by decarboxylation (CuSOg-quinoline, 285 °Q to the known 2,3,5,6-tetrafluoro-l,4-diphenoxybenzene. The preparation in good yield of several polyfluoro-(diphenyl ethers) from polyfluoroarenes and sodium polyfluorophenoxides... 

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