Regioselective hydroformylation vinyl ethers

Polo A, Claver C, Castillon S, Ruiz A, Bayon JC, Real J, Mealli C, Masi D (1992) Regioselective hydroformylation of cyclic vinyl and allyl ethers with rhodium catalysts. Critical influence of the size of the phosphorus cocatalyst. Organometallics 11 3525-3533... 

Regioselectivity in the hydroformylation of vinyl ethers is strongly dependent on the reaction conditions (Scheme 4.23). Thus in an early attempt, du Pont claimed... 

The regioselective hydroformylation of vinyl-aryl ethers to give aldehydes with potential value as aromatic compounds was patented by BASF (Scheme 6.72)... 

Systematic studies on the influence of temperature on the regioselectivity in the hydroformylation of vinyl substrates in the presence of unmodified rhodium-hased precursors have been carried out only in few cases. In particular the investigations reported in literature concern the hydroformylation of styrene, ethyl- and allyl ethers and 1-hexene, with RJi4(CO)i2 over temperatures, ranging from 20 °C to 100 °C. 

A comparison between experimental and MO data on regioselectivity concerning the hydroformylation of several vinyl substrates (propene, 2-methylpropene, 1-hexene, 3,3-dimethylbutene, fluoroethene, 3,3,3-trifluoropropene, vinyl methyl ether, allyl methyl ether, styrene) with unmodified rhodium catalysts was reported. The activation energies for the alkyl rhodium intermediate formation, computed at either level along the pathways to branched or linear aldehydes, allowed one to predict the regioselectivity ratios. Steric effects may be less important for the unmodified carbonyl complexes and electronic factors dominate, assuming that alkene insertion in Rh-H is irreversible. 

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