Synthesis of α-Heteroarylpropanoic Acid via Asymmetric Hydroformylation Catalyzed by Rh(I)-(<i>R</i>,<i>S</i>)-BINAPHOS and the Subsequent Oxidation^‡

The asymmetric hydroformylation of vinyl heteroarenes (vinylfurans and vinylthiophenes) was investigated by using Rh(I)-BINAPHOS derivatives as a catalyst. The hydroformylation of vinylthiophenes 1 gave the corresponding branched aldehydes 2 with high enantiopurities as major products. Oxidation of the aldehydes 2 successfully afforded α-heteroarylpropanoic acids 4 in good yields. In addition, the aldehydes 2 were reduced to alcohols 5 without loss of enantiomeric excess.