FACTORS AFFECTING REGIOSLECTIVITY IN THE RHODIUM-CATALYSED HYDROFORMYLATION OF VINYL ETHERS

Article abstract of DOI:10.1016/0022-328X(85)80321-1

The rhodium catalysed hydroformylation of vinyl ethers ROCH=CH2, where R is an alkyl, a benzyl or a phenyl group, has been investigated over the 20-100 deg C temperature range in the presence of Rh4(CO)12 or 2/PPh3 (1/6) as catalytic precursors.A mixture of 2-alkoxy-(or phenoxy)propanal (the α-isomer) and 3-alkoxy-(or phenoxy)propanal (the β-isomer) is obatined in good yield.The isomeric composition of the aldehydes depends on the structure of the substrate, on the catalytic precursor employed, and on the reaction temperature.The α-isomer predomines in all the cases, its predominance being greater (i) at low temperatures, (ii)in the presence of Rh4(CO)12 as catalyst precursor, and (iii) when a phenyl group is present in the β or γ position with respect to the double bond in the substrate.Electronic factors arising from the presence in the substrate of the oxygen atom and a phenyl group are more impotrant than the steric hindrance of tghe R group in detrmining the regioselectivity of the reaction.