ABSTRACT
Mono- or dideprotonation at the N-H groups of the Noyori ketone hydrogenation catalyst trans-[RuH2((R)-BINAP)((R,R)-dpen)] (1a) yields trans-M[RuH2((R,R)-HNCH(Ph)CH(Ph)NH2)((R)-BINAP)], where M = K(+)(8-K) or Li(+) (8-Li), or trans-M2[RuH2((R,R)-HNCH(Ph)CH(Ph)NH)((R)-BINAP)], where M = Li(+) (8-M'2), which have unprecedented activity toward the hydrogenation of amide and imide carbonyls at low temperatures in THF-d8. Details of the origins of the enantioselection for the desymmetrization of meso-cyclic imides by hydrogenation with 8-K are also described herein.
Subject(s)
Alcohols/chemical synthesis , Amides/chemistry , Imides/chemistry , Ketones/chemistry , Organometallic Compounds/chemistry , Temperature , Alcohols/chemistry , Catalysis , Hydrogenation , Molecular Structure , Ruthenium/chemistry , StereoisomerismABSTRACT
The transition state for the metal-ligand bifunctional addition step in Noyori's enantioselective ketone hydrogenation was investigated using intramolecular trapping experiments. The bifunctional addition between the Ru dihydride trans-[Ru((R)-BINAP)(H)(2)((R,R)-dpen)] and the hydroxy ketone 4-HOCH(2)C(6)H(4)(CO)CH(3) at -80 °C exclusively formed the corresponding secondary ruthenium alkoxide trans-[Ru((R)-BINAP)(H)(4-HOCH(2)C(6)H(4)CH(CH(3))O)((R,R)-dpen)]. Combined with the results of control experiments, this observation provides strong evidence for the formation of a partial Ru-O bond in the transition state.