Olefinic compounds, catalytic hydrogenation

Last but not least, from the process improvement point of view, a research group at Sepracor led by Yun Gao has developed an extremely effective electrocatalytic version of the catalytic AD process (see Section 6D.2.2) [37]. As symbolized in Figure 6D.3, this electrocatalytic approach to AD appears to be ideal. Enantiomerically pure diols arise from electricity, water, and olefins compounds, with hydrogen gas and a little water over the dam as the only byproducts. 

But catalytic reduction of the same phenyl propionic acid gives cis cinnamic acid. Therefore by adding hydrogen under various conditions, one can obtain a desired isomer. The conversion of acetylene into olefinic compounds has been carried out not only for the sake of obtaining the adduct, but Michael studied the various addition reactions for the sake of obtaining a desired product cis or trans. For example, he found that the addition of bromine to acetylene-dicarboxylic acid leads predominantly to the formation of trans isomer. 

Some of these intermediates are analogous to those proposed by Chauvin in olefin metathesis ( Chauvin s mechanism ) [36]. They can be transformed into new olefins and new carbene-hydrides. The subsequent step of the catalytic cycle is then hydride reinsertion into the carbene as well as olefin hydrogenation. The final alkane liberation proceeds via a cleavage of the Ta-alkyl compounds by hydrogen, a process already observed in the hydrogenolysis [10] or possibly via a displacement by the entering alkane by o-bond metathesis [11]. Notably, the catalyst has a triple functionality (i) C-H bond activation to produce a metallo-carbene and an olefin, (ii) olefin metathesis and (iii) hydrogenolysis of the metal-alkyl. 

Another major industrial use of nickel is in catalysis. Nickel and raney nickel are used in catalytic hydrogenation or dehydrogenation of organic compounds including olefins, fats, and oils. 

Olefinic compounds will often insert into carbon-transition metal bonds as CO does, and this reaction is an important step in many catalytic syntheses. When this step is combined with an oxidative addition of an organic halide to a palladium(O) complex in the presence of a base, a very useful, catalytic olefinic substitution reaction results (26-29). The oxidative addition produces an organopalladium(II) halide, which then adds 1,2 to the olefinic reactant (insertion reaction). The adduct is unstable if there are hydrogens beta to the palladium group and elimination of a hydridopalladium salt occurs, forming a substituted olefinic product. The hydridopalladium salt then reforms the... 

Further hydrolysis of the compound 55 with 7% HCl-MeOH followed by treatment with MsCl-pyridine and then with LiCl in dimethyl-formamide (DMF) (90-100°, 18 hr) afforded a monomesylate [56, mp 253-254° (as hydrochloride)] via deacetyldeoxyyuzurimine (57) and dimesylate (58). In the NMR spectrum of 56, a broad singlet resulting from two olefinic protons was observed at 5.93. Finally, catalytic hydrogenation of this compound over Pt02 gave yuzurimine-B mesylate (54) which was directly obtained from yuzurimine-B on mesylation with MsCl-pyridine. 

In the normal oxo reaction a certain amount of hydrogenation occurs, a minor amount of olefins being converted to paraffins in the case of certain olefinic compounds hydrogenation indeed occurs to the exclusion of hydroformylation. It is a remarkable fact that this catalytic reaction occurs in the presence of carbon monoxide and also of sulfur compounds, although cobalt metal is notoriously poisoned by traces of these compounds. The significance of this was pointed out by Adkins and Krsek (23) and Wender, Orchin, and Storch (25) in terms of the concept that the hydroformylation catalyst is a homogeneous one, not sensitive to carbon monoxide or sulfur compounds and in this respect different from usual solid cobalt catalysts. 

Next step of this synthesis consisted in the conversion of alcohol (17) to pisiferic acid (1) and this has been described in Fig. (3). The alcohol (17) in hexane was treated with Pb(OAc)4 in presence of iodine at room temperature to obtain the epoxy triene (19) (51%) whose structure was confirmed by spectroscopy. Treatment of (19) with acetyl p-toluene-sulfonic in dichloromethane yielded an olefinic acetate (20) and this was hydrogenated to obtain (21). The compound (22) could be isolated from (21) on subjection to reduction, oxidation and esterification respectively. The conversion of (22) to (23) was accomplished in three steps (reduction with sodium borohydride, immediate dehydration in dichloromethane and catalytic hydrogenation). Demethylation of (23) with anhydrous aluminium bromide and ethanethiol at room temperature produced pisiferic acid (1). Similar treatment of (23) with aluminium chloride and ethanethiol in dichloromethane yielded methylpisiferate (3). 

The researches of Zal kind were concerned with the catalytic hydrogenation of acetylenic compounds acetylenic glycols add only two hydrogen atoms over palladium and divinylacetylenes add only six hydrogen atoms, the hydrogenation being limited to the formation of olefins (431). 

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