Dehydrogenation products

Jacobs and Craig have made an extended study of the selenium dehydrogenation products of cevine and in addition to cevanthrol and eevanthridine have obtained the following thirteen substances Bases, j3-picoline, 5-methyl-2-ethylpyridinc, 5-methyl-2-hydroxyethylpyridine, base, CgHgON (pierate, m.p. 151-2°), base, CgHjgN (pierate, m.p. 150-1°), base, CggHigN, m.p. 233-5° (methiodide, m.p. 285-290°), base, m.p. 229-230° (methiodide, m.p. 295° (dec.) )... 

The selenium-dehydrogenation products of fsorubijervine have not yet been fully examined, but the two structurally significant products, 5-methyl-2-ethylpyridine and a hydrocarbon, m.p. 135-6°, yielding... 

Solangustidine solangustine, 671 Solanidine, 661, 662, 671, 708, 712, 713 dehydrogenation products, 663 heterocyclic residue, 665 proximate derivatives, 664 structure, 665, 667 Solanine, 661... 

The latest catalyst development is the contact DeH-9, which in terms of activity and stability is comparable with DeH-7 but with improved selectivity (fewer iso- and cycloparaffins and aromatics). This contact has been produced since 1990 and probably used commercially since 1992 [59]. In Table 7 the composition of the dehydrogenation products in relation to the catalyst and the application of the DeFine step is summarized. Table 8 shows the performance data for various catalysts [10] in relation to LAB production. 

Both processes - referring to the non-substituted and substituted methanol reactant- utilize elemental silver catalyst by means of oxidative dehydrogenation. Production is carried out in a pan-like reactor with a 2 cm thick catalyst layer placed on a gas-permeable plate. A selectivity of 95% is obtained at nearly complete conversion. This performance is achieved independent of the size of the reactor, so both at laboratory and production scale, with diameters of 5 cm and 7 m respectively. 

Reinvestigating the reaction of cyclohexanone silyl enol ether 22 with DDQ, adducts were also observed [26]. At 25 °C, both C-C and C-0 adducts (75 and 76) were formed along with the dehydrogenation products 23 and 77. The ratio of... 

The H-NMR data of koumidine are in accord with the proposed structure 12. Furthermore, when koumidine was oxidized with Cr03-H2S04, the product [35, C19H20N2O (M+ 292)] which resulted was a dehydrogenated product of koumidine, and the OH signal disappeared from the H-acetyl... 

Reaction of the thiazine 264 with DDQ in chloroform does not give the dehydrogenated product 265 in every case instead thienoindolizines, 266, may be the observed products. A possible mechanism is shown below < 1987BCJ3713 1992BCJ1244> (Scheme 72). 

Under classical conditions, the reaction between 3 and styrene required 50 h of heating at 110 °C, and gave the dihydropyridazine adduct 10a [24], After SMWI with 30 W incident power for 5 min (Tmax = 154 °C), the adduct 10a was not detected whereas the totally dehydrogenated product, pyridazine 10b, was isolated in almost quantitative yield (Tab. 7.1, entry 8). Ethyl vinyl ether and 3 gave the same product, pyridazine 11, under both classical heating [25] and MW irradiation conditions (Tab. 7.1, entry 9). In this instance the DA adduct lost nitrogen and ethanol. 

In the absence of a chelating group in the substrate, no carbonylation product was detected and an acceptable yield of the dehydrogenated product was reported (Equation (49)).52... 

The ions Sm+, Eu+, Tm+, and Yb+ form addition complexes with 1,3,5-tri-ferf-butylbenzene (130), whereas other lanthanide ions form dehydrogenation products (see Section III.A.2). 

The Ti+ ions, produced by using a laser vaporization source (cooled by collisions with He) have been reacted with NH3 to produce the dehydrogenated product ions, [TiNH]+ (100). Many early transition metal ions and Os+ produce the [MNH]+ ion (9,106). The ion [TiNH]+ was reactive toward NH3 and increasing the concentration of NH3 in the drift tube (100) allowed up to four NH3 molecules to add to the [TiNH]+ ion, thus producing five-coordinate Ti in the gas phase. 

Moro-Oka et al. (1976) have reported that the oxidation of 9,10-dihydroanthracene by K02 solubilized in DMSO by 18-crown-6 gives mainly the dehydrogenated product, anthracene. Under the same conditions, 1,4-hexadiene is dehydrogenated to benzene. The authors proposed a mechanism in which the superoxide ion acts as a hydrogen-abstracting agent only. The oxidations of anthrone (to anthraquinone), fluorene (to fluorenone), xanthene (to xanthone) and diphenylmethane (to benzophenone) are also initiated by hydrogen abstraction. 

Washing with chloroform is necessary to dissolve some of the stilbene which crystallizes out with the hydroquinone. In many reactions, washing the hydroquinone with hot benzene is sufficient, as the dehydrogenation products crystallize to a limited extent from dioxane. 

Tables V and VI show that the distribution of molecular types in the liquid products after cracking at 500° and 560°C shifts towards more aromatics, particulary monoaromatics, and polars with increasing boiling point range of the feed. The yields of monoaromatics increase at the higher temperature since they are favoured thermodynamically as dehydrogenation products of naphthenes. Polyaromatics are rejected to coke. The conversion of polars decreases with increasing boiling point of the feed at 500°C, but increases...

Azirines are dimerized under various conditions to dihydropyrazines or their dehydrogenated products, namely pyrazines (Section 8.03.9.5). Quinoxalines are oxidized with potassium permanganate to afford 2,3-pyrazinedicarboxylic acids, and pteridines are hydrolyzed to give 3-amino-2-pyrazinecarboxylic acid derivatives. Condensation of 3,4-diamino-l,2,5-thiadiazole 176 with a-diketones produces l,2,5-thiadiazolo[3,4- Jpyrazines 177, which are reduced to provide 2,3-diaminopyrazines 178 (Scheme 51) <1997JCM250>. 

The yield of unimolecularly formed cyclohexene, and by that the yield of unimolecular H2 elimination (quantum yield in photolysis or G value in radiolysis), XiWj), may be calculated from the yields of alkene and dimer dehydrogenation products by the relation [91,92] ... 

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