Hydroformylation unfunctionalized alkenes

From a regio- and chemoselectivity point of view, the behavior of this class of alkenes is very similar to that observed with unfunctionalized alkenes in biphasic medium. As expected for a biphasic medium, the catalytic activities are comparable with or lower than those observed under similar homogeneous conditions, and strongly dependent on the water-solubility of the alkene. Addition of solubilizing agents is often necessary for high-molecular-mass alkenes. For instance, low-mo-lecular-mass co-alkenecarboxylic acid methyl esters such as methyl 4-pentenoate can be hydroformylated efficiently in biphasic systems whereas methyl esters of higher w-alkenecarboxylic acids such as methyl 13-tetradecenoate require the presence of surfactants (Eq. 1) [9]. 

The behavior of functionalized alkenes depends strongly on the proximity of the functional group relative to the double bond to be hydroformylated. The few examples described so far reveal that most of the principles used for the hydroformylation of unfunctionalized alkenes can be applied. However, unusual results can be observed with a-functionalized alkenes, i.e., with acrylates. The formation of reactive nonchelated species has been suggested as an explanation of this behavior. Such a phenomenon should probably be generalized to other alkenes bearing functional groups in a suitable position, but experiments still remain to be done under biphasic conditions to confirm this hypothesis. 

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