Asymmetric Hydrogenation of Olefins with Aprotic Oxygen Functionalities Catalyzed by BINAP-Ru(II) Complexes

Article abstract of DOI:10.1021/jo00107a014

Cyclic α,β-unsaturated ketones, alkylidene lactones, and alkenyl ethers have been hydrogenated in high enantiomeric excesses by use of BINAP-Ru(II) complexes (BINAP = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl) as catalysts. 2-Alkylidenecyclopentanones were hydrogenated in the presence of Cl, Ru2Cl4(BINAP)2(NEt3), or Ru(OCOCH3)2(BINAP) in up to 98percent ee, while in the case of 2-benzylidene- and 2-(3-phenylpropylidene)cyclopentanones, enantiomeric excesses of the hydrogenation were below 50percent under the same conditions.The sense of asymmetric induction as well as the enantioselectivity (95percent ee) obtained in the hydrogenation of (E)-2-propylidene-γ-butyrolactone were the same as those of the (Z)-isomer.Lactones, 2- and 4-alkylidene-γ-butyrolactones, were converted to the corresponding saturated γ-butyrolactones in 95percent ee.Hydrogenation of diketene with the catalytic system derived from (benzene)>Cl and triethylamine or complex Ru2Cl4<(S)-BINAP>2(NEt3) established a new synthetic route to (R)-4-methyl-2-oxetanone, a promising monomer of biodegradable polymers, in up to 97percent selectivity and 92percent ee.Alkenyl ethers, 2-methylenetetrahydrofuran, and 2-methyl-3,4-dihydrofuran have also been hydrogenated to give 2-methyltetrahydrofuran in 91 and 87percent ee, respectively.