Catalytic hydrogenation

Catalytic hydrogenation reaction is generally divided into catalytic hydrogenating reaction, catalytic hydrogenolysis reaction and catalytic hydrogen transfer reaction.

(1) Catalytic hydrogenating reaction

It refers to the addition of one or several unsaturated functional groups in the organic compounds with the hydrogen under the action of catalyst, and it is a class of reaction having the most widely used precious metal catalyst; it can reduce C-C, C-O, C-N, N-O and other unsaturated functional groups in the organic matter by the means of hydrogenation and can use this technology to produce many chemicals.

Catalytic hydrogenation reactions follow these rules:

* Alkynes> diolefins> olefins> aromatics

* The more substituted hydrocarbons on the benzene ring, the more difficult the hydrogenation

* The hydrogenation of aldehyde, ketone, acid or ester can form the alcohol in all cases, but the formation condition for aldehyde is easier than that for ketone, and the condition for esters is easier than that for acids

* The hydrogenation for those with the smallest steric hindrace is preferred

* The hydrogenation for exocyclic double bond is easier than that for endocyclic double bond.

The equilibrium constant of the hydrogenation reaction decreases with the increase of the reaction temperature. When the temperature rises, the reaction is faster. When Kp decreases by big amount, by-product numbers high, so the appropriate temperature is critical for the hydrogenation reaction.

When H2 pressure increases, Kp increases and the reaction speed is accelerated. However, if the reaction product is strongly adsorbed on the catalyst, it will happen that the higher the product partial pressure, the slower the reaction.  

The self-developed hydrogenation catalysts are as follows:

* Special nitro reduction catalyst with high activity, wide selectivity and reusability

* Platinum-carbon catalyst for halogenated nitro reduction with wide selectivity and low dehalogenation rate  

* Special platinum-carbon catalyst for steroids synthesis

* Special platinum-carbon catalyst of tetrahydrofuran with high activity

* Special dehalogen catalyst with high activity and toxin immunity

* Special sulfur-resisting palladium-carbon catalysts

* Special acid-stable palladium-carbon catalyst

* Special doxycycline palladium-carbon catalyst

* Special azithromycin palladium-carbon catalyst

* Special platinum-carbon catalyst for unsaturated aldehyde ketone selective hydrogenation

* Special dehydrogenation catalyst  

* Special 3-4% platinum-carbon catalyst of disproportionated rosin

* Special platinum-carbon catalyst of hydrogenated rosin

* Special 5% platinum-carbon catalyst of orlistat

* Special 5% platinum-carbon catalyst of indene worm intermediates

* Special 5% ruthenium-carbon catalyst of  L-amino propanol

* Special MDA synthesis catalyst

* Special fourier content catalyst

* Special 5-nitrobenzene and imidazole ketone catalyst

* Special vitamin E catalyst

(2) Catalytic Hydrogenolysis Reactions

In the hydrogenation reaction, the reduction of the σ bond is called hydrogenolysis, that is, during the hydrogenation process, some atoms or groups are removed and replaced by hydrogen atoms.

Hydrogenation reaction can be divided into different types of disjunction, dehalogenation, ring opening, decarboxylation and desulfurization and others resulted from the breaking apart of chemical bonds like the carbon-carbon bond, carbon-oxygen bond, sulfur-oxygen bond, carbon-nitrogen bond, carbon-sulfur bond, carbon-halogen bond, carbon-hydrogen bond, carbon-carbon bond, nitrogen-oxygen bonds, nitrogen-nitrogen bonds and oxygen-oxygen bonds. Hydrogenolysis is used mainly for the reduction of certain groups (such as the reduction of amine from nitro group, nitroso group, etc.), the removal of some groups (such as dehalogenation, desulfurization, etc.), and the removal of certain protective groups where catalytic hydrogenolysis is commonly presented. Catalytic hydrogenolysis is also one of the widely used methods and techniques in organic synthesis. Many of these chemicals can be synthesized by this technique as alkyl group, benzyl group, amino group and carbon-halogen single bond of some groups in the compound are prone to be hydrogenated.

The self-developed catalysts for special usages are as follows:  

* Special x-penem catalyst with a yield rate or more than 50-52% for synthesis of meropenem, imipenem, ertapenem, and biapenem and more

* Special moxifloxacin synthesis catalyst

* Special debenzylation protective group catalyst

* De-Cbz, PNB, NBoc, and BnOR catalysts and more.

(3) Catalytic Hydrogen Transfer Reaction

Certain organic compounds can become hydrogen donors in the presence of a catalyst and release hydrogen quantificationally. This process is called catalytic transfer hydrogenation. Although it is not as common as reactions involving catalysts of hydrogen or metal, its unique characteristics makes it an important organic synthesis method. This type of reaction can be divided into three categories:

* Reactions where the migration of hydrogen occurs in the same molecule;

* Reactions where hydrogen is redistributed (transferred) in the same donor and acceptor;

* Reactions where hydrogen is transferred, or dehydrogenation-hydrogenation takes place between the different donor and acceptor.

Catalytic transfer hydrogenation is very similar to catalytic hydrogenation but with different hydrogen sources.

Catalytic Transfer Hydrogenation has the following characteristics:

* Mild reaction conditions with no requirement for pressure;

* Simple operation with no requirement for special equipment;

* A wide range of selections are enabled.

Catalytic transfer hydrogenation is related to hydrogen donor, acceptor, catalyst, solvent, reaction temperature and reaction medium. And most reactions need to be carried out at higher temperatures and the higher the temperature, the faster the reaction.

We have self-developed the special medroxyprogesterone hydrogen transfer catalyst.