Dehydrogenation with simultaneous

Dehydrogenation with simultaneous migration of the carbon double bond... 

If it is the first intermediate, it can be speculated that the 2,3-dihydroxy-tryptophan, by dehydrogenation with simultaneous ring opening, could yield formylkynurenine. This is a hypothesis which remains to be proved. 

Another interesting reaction of benzoxazines 114 (115) is the reductive opening of the oxazine ring with simultaneous dehydrogenation of the pyrazoline moiety [170]. This process is carried out in a KOH suspension of a mixture of dimethyl sulfoxide and dimethylformamide. For instance, this treatment involving 2,5-diary l-l,10b-dihydro-177-pyrazolo[l,5-c]benzo[e]-l,3-oxazines 116 leads to the formation of pyrazoles 117 (Scheme 2.32). Similar disproportionation reactions have also been described for some bezopiranes, for example, pyrazole derivative 118 [91, 170]. 

Agaskar, P.A. Grasselli, R.K. Michaels, J.N. Reischman, P.T. Stern, D.L. Tsikoyiannis, J.G Process for the Catalytic Dehydrogenation of Alkanes to Alkenes with Simultaneous Combustion of Hydrogen. US Patent 5,430,209, Jul 4, 1995 (assigned to Mobil Oil Corp.). 

Heating a 3-(2-hydroxyphenyl)propionate ester in diphenyl ether with palladium-charcoal induces a combined cyclization and dehydrogenation [3437], Simultaneous de-O-benzylation and cyclization of a 2-(benzyloxy)acrylic acid by heating with acetyl chloride containing phenyltrimethylammonium iodide gives good yields of a fused pyran-2-one [3836]. In contrast, an o-methoxy-benzylidenemalonic acid (as its potassium salt) cyclizes in the cold when treated with trifluoroacetic acid-trifluoroacetic anhydride [3938]. 

Azomethines are formed by way of addition products, RR CH—NR"OH. In certain cases, however, these may be dehydrogenated by the nitroso compound to the nitrones, with simultaneous formation of azoxy compounds 434 435... 

Zelinsky118 found that the three isomeric methylcyclohexenes are dehydrogenated to toluene when passed over a palladium catalyst at the relatively low temperature of 116-118°, with simultaneous formation of methylcyclo-hexane. This phenomenon, that unsaturated compounds give aromatic and perhydrogenated systems at relatively low temperatures, i.e., disproportionation, is often observed during catalytic dehydrogenation, so that the theoretical... 

Benzyl nitriles. 2 eqs. 2,3-dichloro-5,6-dicyanoquinone rapidly added to a soln. of 2-( -methoxyphenyl)butane and trimethylsilyl cyanide in methylene chloride, and the mixture stirred at 60° for 24 h - product. Y 68%. F.e. and with simultaneous dehydrogenation/aromatization s. M. Lemaire et al., Chem. Letters 1988, 1581-4. 

Although of no current importance grain alcohol was a major raw material for butadiene production during World War II in both Russia and the United States. One method of conversion involved dehydrogenation to acetaldehyde and combination of the latter with further ethyl alcohol with simultaneous dehydration. 

Selective hydrogenation of N-heterocycles, also with simultaneous formation of sec. alcohols from ketones or subsequent partial dehydrogenation... 

Burshtein, Pshenichnikov, and co-workers [105] found that the stoichiometric composition of ethane adsorbed on a Pt /Pt electrode at 90°C in 1 N sulfuric acid solution varied with time from C H = 1 2 to C H = 1 1. The change in the C H ratio was attributed to slow and more intense dehydrogenation of the adsorbed particles, with simultaneous formation of methane ... 

The aniline then reacts with the ap-unsaturated aldehyde by 1 4-addition the addition product, under the influence of strong acid, cyclises to form 1 2-dihydroquinaldine. The latter is dehydrogenated by the condensation products of aniline with acetaldehyde and with crotonaldehyde simultaneously produced ( .c., ethylideneaniline and crotonylideneaniline) these anils act as hydrogen acceptors and are thereby converted into ethylaniline and n-butyl-aniline respectively. 

Purely parallel reactions are e.g. competitive reactions which are frequently carried out purposefully, with the aim of estimating relative reactivities of reactants these will be discussed elsewhere (Section IV.E). Several kinetic studies have been made of noncompetitive parallel reactions. The examples may be parallel formation of benzene and methylcyclo-pentane by simultaneous dehydrogenation and isomerization of cyclohexane on rhenium-paladium or on platinum catalysts on suitable supports (88, 89), parallel formation of mesityl oxide, acetone, and phorone from diacetone alcohol on an acidic ion exchanger (41), disproportionation of amines on alumina, accompanied by olefin-forming elimination (20), dehydrogenation of butane coupled with hydrogenation of ethylene or propylene on a chromia-alumina catalyst (24), or parallel formation of ethyl-, methylethyl-, and vinylethylbenzene from diethylbenzene on faujasite (89a). 

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