Hydrogenation during hydroformylation

The composition of the products of reactions involving intermediates formed by metaHation depends on whether the measured composition results from kinetic control or from thermodynamic control. Thus the addition of diborane to 2-butene initially yields tri-j iAbutylboraneTri-j -butylborane. If heated and allowed to react further, this product isomerizes about 93% to the tributylborane, the product initially obtained from 1-butene (15). Similar effects are observed during hydroformylation reactions however, interpretation is more compHcated because the relative rates of isomerization and of carbonylation of the reaction intermediate depend on temperature and on hydrogen and carbon monoxide pressures (16). 

It has been known for many years that transition metals catalyze reactions of coordinated phosphines (2). Known reactions of phosphines as ligands include carbon-hydrogen lx)nd cleavage (cyclometalation), as well as direct carbon-phosphorus bond cleavage. Such metal-catalyzed reactions of phosphines lead to formation of new metal complexes which can affect catalyst properties. A known example is the reaction of triphenylphosphine to propyldiphenylphosphine during the rhodium-catalyzed propylene hydrogenation or hydroformylation (5). 

Hydrogenation of the olefin reactant and the aldehyde products are important competing side reactions during hydroformylation. 

Approximately 1% of the olefin is hydrogenated to paraffin during hydroformylation. 

Rhodium carbonyi clusters. 13,288 15, 334 18, 305-306 19, 280-281 20, 317-318 Hydroformylation. A phosphine plays a crucial role to suppress hydrogenation during hydxoformylation of 4-vinylpyridine. The A-vinyl group of a divinylpyrrole can be retained to achieve selective hydroformylation of a carbon-linked vinyl residue. ... 

The cluster [MoCoNi( 3-CMe)Cp2(CO)s] (11) was found to isomerize 1-pentene, a competition reaction observed during hydroformylation catalysis, and hydrogenate 2-pentene and styrenesj ° ° Hydroformylation of styrene was also inves-... 

The formation of more than two aldehyde isomers can also be expected if hydrogen shift on the substrate occurs during hydroformylation of internal olefins. 

During hydroformylation, acetalization of aldehydes can take place as an undesired side reaction when the hydroformylation is conducted in alcohols as solvent and under the influence of a hydroformylation catalyst with acidic properties. Moreover, when alcohols result in a hydroformylation-hydrogenation tandem reaction (see Section 5.2), acetalization has always been taken into consideration. 

Fatty acid compounds usually contain single or multiple double bonds with varying E/Z geometries. Under hydroformylation conditions, they can be hydrogenated before hydroformylation takes place [21]. A special problem is Z/ isomerization or the migration of double bonds, since most hydroformylation catalysts are also active isomerization catalysts. Isomerization may take place before, during, or after (multiple double bonds ) the reaction with syngas. 

---