Hydroformylation of allyl ethers. A study of the regioselectivity using rhodium catalysts

The hydroformylation of different substituted allyl benzyl ethers is studie d using the precursor catalytic system [Rh(mu-S(CH2)(3)NMe2)(cod)](2) + PR3 (R = Ph, O-o-t-BuC6H4) in order to obtain gamma-, beta- and alpha-hydroxya ldehydes. The influence of the phosphorus auxiliary ligands on the isomeriz ation/hydroformylation processes is analyzed. High yields and low regiosele ctivities are obtained in the hydroformylation of allyl benzyl ether 1 usin g both P(O-o-t-BuC6H4)(3) and PPh3. 4-Benzyloxy-3-methyl-butanal 8 and 4-be nzyloxy-2-methyl-butanal 11 were obtained in good to excellent yields, star ting from benzyl-2-metallyl ether 2 and benzyl-2-buthenyl ether 3, respecti vely. (C) 1999 Elsevier Science B.V. All rights reserved.