A series of 16-electron Cp*Ir amide complexes with C-N chelating ligands, Cp*Ir[κ 2 (N,C)-(NHCR 2 -2-C 6 H 4 )] (2a: R ) C 6 H 5 , 2b: R ) CH 3 ), and the chiral version, Cp*Ir[κ 2 (N,C)-(R)-{NHCH(CH 3 )-2-C 10 H 6 }] (2e), were obtained in good to excellent yields from reactions of 18-electron iridium amine complexes, Cp*IrCl[κ 2 (N,C)-(NH 2 CR 2 -2-C 6 H 4 )] (1a: R ) C 6 H 5 , 1b: R ) CH 3 ) and Cp*IrCl[κ 2 (N,C)-(R)-{NH 2 CH(CH 3 )-2-C 10 H 6 }] ( 1e), with a base. The amido complexes 2 readily reacted with 2-propanol to convert into hydrido(amine) complexes 3 in almost quantitative yields. The chiral amido complex has proven to serve as an efficient catalyst for asymmetric transfer hydrogenation of acetophenone with 2-propanol, giving 1-phenylethanol with a moderate ee. The Brønsted basicity on the metal-NH moiety in the amido complexes was evaluated by deprotonation of acetic acid, dimethyl malonate, and acetone, leading to the corresponding acetato(amine) complex 4 and alkyl(amine) complexes 5 and 6, respectively, indicating that the amido-Ir complexes bearing the C-N chelate have more basic properties than those with N-sulfonylated diamine ligands.

Catalytic hydrogen transfer between alcohols and ketones offers a great opportunity to explore an attractive molecular transformation because of its low cost and operational simplicity.[1] We have developed chiral bifunctional Ru, Rh, and Ir hydride complexes-[RuH(Tsdpen)(h 6 -arene)] and [Cp*MH(Tsdpen)] (TsDPEN: N-(p-toluenesulfonyl)-1,2-diphenylethylenediamine, Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl, M = Rh, Ir) as practical catalysts for the asymmetric transfer hydrogenation of ketones.[1a-d, 2] The amine-hydrido complex has a sufficiently acidic NH proton to activate ketones, leading to the amido complex along with the formation of the reduction products. The resulting amido complex readily dehydrogenates alcohols to regenerate the amine-hydrido complex (Scheme 1). Because of its intrinsic reversible nature, both forward and reverse reactions can be utilized as the reduction of ketones and oxidation of alcohols, respectively. However, the dehydrogenative oxidation reaction with the related amine/amido catalysts has been investigated less, mainly because of the lack of appropriate hydrogen acceptors, except for ketones for the kinetic resolution of racemic alcohols, [3] intramolecular redox isomerization, [4] and other oxidative transformations. [5] We have extended a conceptually new hydrogen-transfer protocol with bifunctional catalysts and found that molecular oxygen readily reacts with the amine-hydrido complex leading to the amido complex. Based on the present new finding, [6] we could successfully apply the aerobic oxidation to the kinetic resolution of racemic secondary alcohols with chiral bifunctional Ir, Rh, and Ru catalysts, in which O 2 serves as a hydrogen acceptor.The newly developed {Cp*Ir} hydride complex 1 a [7] bearing a C-N chelate primary amine ligand prepared from triphenylmethylamine reacts rapidly with O 2 or air under mild conditions to give the corresponding amido complex 2 a (Scheme 2). Monitoring a solution of 1 a in [D 8 ]THF under air at room temperature by 1 H NMR spectroscopy showed a rapid decrease in the intensity of a hydride signal at d = À13.12 ppm and an increase in the characteristic signal due to the NH moiety of 2 a at d = 8.37 ppm, indicating the smooth conversion to the amido complex (70 % yield based on 1 a) by the action of O 2 .Other oxidants like hydroperoxides also promoted the transformation to 2 a. The reaction of 1 a with an equimolar amount of H 2 O 2 in [D 8 ]THF for 24 h gave 2 a in 95 % yield in addition to a detectable amount of H 2 O. The O À O bond cleavage of peroxides with the hydrido complex 1 a was also clearly demonstrated in the treatment of tBuOOH, which afforded 2 a and tBuOH (26 % yield). Although the precise mechanism of the formation of 2 a from 1 a in the presence of O 2 has remained unclear, these findings as well as recently reported results [6] imply that the reaction of 1 a with O 2 might proceed through O 2 insertion into the metal-hydride bond [8] to form an amine-hydroperoxo complex, followed by the release of 2 a and H 2 O 2 ...

The aerobic oxidation of alcohols with a family of bifunctional Ir, Rh, and Ru complexes bearing C-N chelating ligands derived from primary benzylic amines was investigated. The isolable amido-Ir complexes [Cp*Ir{kappa(2)(N,C)-(NHCR(2)-2-C(6)H(4))}] (R=C(6)H(5), CH(3); Cp*=1,2,3,4,5-pentamethylcyclopentadienyl) effected the oxidation of secondary alcohols smoothly under atmospheric pressure of air at 30 degrees C in THF to give the corresponding ketones in good yields. The hydrido(amine)-Ir complexes [Cp*IrH{kappa(2)(N,C)-(NH(2)CR(2)-2-C(6)H(4))}] and the combined catalyst system involving the chloro(amine)-Ir complex [Cp*IrCl{kappa(2)(N,C)-(NH(2)CR(2)-2-C(6)H(4))}] and KOC(CH(3))(3) were also found to be effective catalysts, whereas the tertiary amine complex [Cp*IrCl{kappa(2)(N,C)-(N(CH(3))(2)CH(2)-2-C(6)H(4))}], which does not have a metal/NH moiety, did not show catalytic activity. The employment of primary alcohols in the aerobic reaction with the Cp*IrCl complex and KOC(CH(3))(3) resulted in the formation of esters through oxidative dimerization.

Catalytic hydrogen transfer between alcohols and ketones offers a great opportunity to explore an attractive molecular transformation because of its low cost and operational simplicity.[1] We have developed chiral bifunctional Ru, Rh, and Ir hydride complexes-[RuH(Tsdpen)(h 6 -arene)] and [Cp*MH(Tsdpen)] (TsDPEN: N-(p-toluenesulfonyl)-1,2-diphenylethylenediamine, Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl, M = Rh, Ir) as practical catalysts for the asymmetric transfer hydrogenation of ketones.[1a-d, 2] The amine-hydrido complex has a sufficiently acidic NH proton to activate ketones, leading to the amido complex along with the formation of the reduction products. The resulting amido complex readily dehydrogenates alcohols to regenerate the amine-hydrido complex (Scheme 1). Because of its intrinsic reversible nature, both forward and reverse reactions can be utilized as the reduction of ketones and oxidation of alcohols, respectively. However, the dehydrogenative oxidation reaction with the related amine/amido catalysts has been investigated less, mainly because of the lack of appropriate hydrogen acceptors, except for ketones for the kinetic resolution of racemic alcohols, [3] intramolecular redox isomerization, [4] and other oxidative transformations. [5] We have extended a conceptually new hydrogen-transfer protocol with bifunctional catalysts and found that molecular oxygen readily reacts with the amine-hydrido complex leading to the amido complex. Based on the present new finding, [6] we could successfully apply the aerobic oxidation to the kinetic resolution of racemic secondary alcohols with chiral bifunctional Ir, Rh, and Ru catalysts, in which O 2 serves as a hydrogen acceptor.The newly developed {Cp*Ir} hydride complex 1 a [7] bearing a C-N chelate primary amine ligand prepared from triphenylmethylamine reacts rapidly with O 2 or air under mild conditions to give the corresponding amido complex 2 a (Scheme 2). Monitoring a solution of 1 a in [D 8 ]THF under air at room temperature by 1 H NMR spectroscopy showed a rapid decrease in the intensity of a hydride signal at d = À13.12 ppm and an increase in the characteristic signal due to the NH moiety of 2 a at d = 8.37 ppm, indicating the smooth conversion to the amido complex (70 % yield based on 1 a) by the action of O 2 .Other oxidants like hydroperoxides also promoted the transformation to 2 a. The reaction of 1 a with an equimolar amount of H 2 O 2 in [D 8 ]THF for 24 h gave 2 a in 95 % yield in addition to a detectable amount of H 2 O. The O À O bond cleavage of peroxides with the hydrido complex 1 a was also clearly demonstrated in the treatment of tBuOOH, which afforded 2 a and tBuOH (26 % yield). Although the precise mechanism of the formation of 2 a from 1 a in the presence of O 2 has remained unclear, these findings as well as recently reported results [6] imply that the reaction of 1 a with O 2 might proceed through O 2 insertion into the metal-hydride bond [8] to form an amine-hydroperoxo complex, followed by the release of 2 a and H 2 O 2 ...

Die elektrolytische Benzoyloxylierung von NN‐distibstituierten Fomiamiden (II) mit Benzoesäure (I) in Acetonitril ergibt in Gegenwart von Tetraäthylammoniilmperchlorat die Esteramide (III), wobei die Ausbeuten mit zunehmender Raumerfüllung der Substituenten sinken.