Palladium tetralin

Palladium is the most active and most frequently used catalyst in transfer hydrogenations.77 78 Cyclohexene, a cheap, readily available, highly reactive molecule, is the preferred donor compound. Alternatively, tetralin and monoterpenes and, in general, any hydroaromatic compound, may be used. Mainly alcohols are employed as the donor with Raney Ni. 

Traces of 1(9)- and 9(10)-octalin are also detected. Under suitable conditions, the reaction may stop at tetralin on nickel and palladium.67... 

Chromium carbene complexes, 82 Palladium(II) chloride, 234 Tetralins... 

On being heated in an inert solvent (e.g., tetralin) at 180°-200°, benzo[6]thiophene-1,1-dioxide affords 6a, 1 la-dihydrobenzo[6]naph-tho[l,2-d]thiophene-7,7-dioxide (347a) through formation of the intermediate adduct 349, which readily loses sulfur dioxide.377,479, 729,730 kinetics of this self-condensation in various solvents have been studied recently.730 The product (347a) may be aromatized with palladium-charcoal,377-479 or by treating its dibromide with base,729 to give the sulfone (348a) of benzo[6]naphtho[l,2-d]thiophene, which... 

This reaction [Eq. (30)] has been carried out classically by heating almost any saturated isoquinoline with 10% palladium-on-carbon (sometimes 5% and sometimes up to 30%)48 in a high boiling solvent such as xylene or tetralin.73 It has been applied to 4-hydroxy-9 and 4-ethoxytetrahydroisoquinolines.18 The yields are often erratic, however, and the reaction is not very satisfactory. 

There are two main synthetic routes to naphthalene the Haworth synthesis and a Diels-Alder approach. In the Haworth synthesis (Scheme 12.1), benzene is reacted under Friedel-Crafts conditions with succinic anhydride (butanedioic anhydride) to produce 4-oxo-4-phenylbutanoic acid, which is reduced with either amalgamated zinc and HCl (the Clemmensen reduction) or hydrazine, ethane-1,2-diol and potassium hydroxide (the Wolff-Kischner reaction) to 4-phenylbutanoic acid. Ring closure is achieved by heating in polyphosphoric acid (PPA). The product is 1-tetraione and reduction of the carbonyl group then gives 1,2,3,4-tetrahydronaphthalene (tetralin). Aromatization is achieved by dehydrogenation over a palladium catalyst. 

Selective catalytic hydrogenation of an acyl chloride to an aldehyde can be accomplished with varying yields the method has been reviewed. The preferred catalyst is palladium suspended on barium sulfate. The reaction may be carried out in the liquid phase by bubbling hydrogen through a hot solution of the acyl chloride in xylene or tetralin in which... 

Cocker et al found the tetralin derivative (1) to be dehydrogenated normally by sulfur at 230-240° but to lose the n-buty1 group to give (3) on reaction with selenium at 330-350°. Dehydrogenation with palladium charcoal at 260-280° gave a mixture of (2) and (3). 

Traces of octalins were always present during the hydrogenation of tetralin or naphthalene (3). Observed concentrations of octalins are listed in Table IV. The amounts were particularly small with palladium catalysts. One of the unique characteristics of palladium is its ability to adsorb and saturate olefins in the presence of aromatics or, conversely, its relative inability to adsorb and saturate aromatics in the presence of olefins. By way of contrast, some other metals, particularly ruthenium and rhodium, are more able to adsorb and saturate aromatics in the presence of olefins. Whatever the nature of the adsorbed state of naphthalene that leads to hydrogenation, one could imagine the possibility of two isomeric forms—one of which behaved more like an adsorbed olefin and the other more like an adsorbed aromatic ... 

Concentrations of total octalins are plotted in Fig. 6 as a function of conversion beyond the tetralin stage. The sharp drop in octalin content in early stages of the reaction is largely due to easy saturation of octalins other than A i -octalin. Extrapolation toward zero conversion suggests that most or all of the decalins have octalin precursors. The curves fall generally into two families depending on the rates of saturation of the octalins relative to tetralin. With rhodium, and to a lesser extent with ruthenium, the lined-out concentration remains high, due primarily to the accumulation of A -i -octalin. With palladium, platinum, and iridium, the initial octalin concentrations fall precipitously and line out at low values because all octalin isomers are adsorbed and saturated rapidly relative to tetralin. 

Data for the 1,3-dimethyldecalins are in Table XXIX. Key information was obtained by separately hydrogenating cis- and trans-1,3-dimethyltetralin. Each of the tetralins was obtained in about 10% yield by hydrogenating 1,3-dimethylnaphthalene over palladium and separating the product with a 15,000-plate GLC preparative column. 

Data for the 1,6-dimethyldecalins are in Table XXXII. The best available sample of 1,6-dimethylnaphthalene contained a few percent of 1,7-dimethylnaphthalene as impurity. Hydrogenation on palladium yielded nearly equal amounts of the isomeric 1,6- and 2,8-dimethyl-tetralins. Retention times were shifted enough (see Fig. 18) so that the separated tetralin isomers contained reduced amounts of the 1,7-impurities. 

Amine lassen sich grundsatzlich hydrogenolysieren, beispielsweise 2-Phenyl-athyla-mine mit 50% d.Th. Mit besseren Ausbeuten verliiuft die Spaltung benzyl- oder al-lyl-aktivierter Amine. So erhalt man aus Benzylamin Oder Tribenzylamin mit Palladium/Kohle und Tetralin bei 205—207° Toluol (85 bzw. 74% d.Th.)1. 

Chlorophenyl)propionic acid A solution of 4-chlorocinnamic acid (5 g) in tetralin (180 ml) containing palladium black (1 g) is heated at the boiling point for 1.5 h in a Kjeldahl flask under an air condenser. The side chain is then completely reduced. The catalyst is filtered off, the acid components are removed from the filtrate in sodium carbonate solution, adhering tetralin is removed from the alkaline solution by ether, the alkaline solution is acidified by hydrochloric acid, and the 3-(p-chlorophenyl)propionic acid that separates is taken up in ether. On evaporation, the pure 3-(p-chlorophenyl)propionic acid of m.p. 123° is obtained. 

Considerably more energetic conditions are required for dehydrogenatioa of perhydrogenated compounds. Thus, whereas tetralin is dehydrogenated in the liquid phase in the presence of platinum or palladium catalysts at 185°, a temperature of at least 300° is necessary for dehydrogenation of decalin.119... 

---