AN EFFICIENT SYNTHESIS OF OPTICALLY-ACTIVE 4-METHYLOXETAN-2-ONE - ASYMMETRIC HYDROGENATION OF DIKETENE CATALYZED BY BINAP RUTHENIUM(II) COMPLEXES [BINAP = 2,2'-BIS(DIPHENYLPHOSPHINO)-1,1'-BINAPHTHYL]

Highly enantioselective hydrogenation of diketene with the catalytic system derived from {RuCl[(S)- or (R)-binap](benzene)}Cl and triethylamine or with Ru2Cl4[(S)- or (R)-binap]2(NEt3) [binap = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl] in tetrahydrofuran gives optically active 4-methyloxetan-2-one in up to 97% selectivity and 92% enantiomeric excess (e.e.).