As a candidate for bifunctional asymmetric catalysts containing a half-sandwich C–N chelating Ir(III) framework (azairidacycle), a dinuclear Ir complex with an axially chiral linkage is newly designed. An expedient synthesis of chiral 2,2′-bis(aminomethyl)-1,1′-binaphthyl (
1) from 1,1-bi-2-naphthol (BINOL) was accomplished by a
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As a candidate for bifunctional asymmetric catalysts containing a half-sandwich C–N chelating Ir(III) framework (azairidacycle), a dinuclear Ir complex with an axially chiral linkage is newly designed. An expedient synthesis of chiral 2,2′-bis(aminomethyl)-1,1′-binaphthyl (
1) from 1,1-bi-2-naphthol (BINOL) was accomplished by a three-step process involving nickel-catalyzed cyanation and subsequent reduction with Raney-Ni and KBH
4. The reaction of (
S)-
1 with an equimolar amount of [IrCl
2Cp*]
2 (Cp* = η
5–C
5(CH
3)
5) in the presence of sodium acetate in acetonitrile at 80 °C gave a diastereomeric mixture of new dinuclear dichloridodiiridium complexes (
5) through the double C–H bond cleavage, as confirmed by
1H NMR spectroscopy. A loss of the central chirality on the Ir centers of
5 was demonstrated by treatment with KOC(CH
3)
3 to generate the corresponding 16e amidoiridium complex
6. The following hydrogen transfer from 2-propanol to
6 provided diastereomers of hydrido(amine)iridium retaining the bis(azairidacycle) architecture. The dinuclear chlorido(amine)iridium
5 can serve as a catalyst precursor for the asymmetric transfer hydrogenation of acetophenone with a substrate to a catalyst ratio of 200 in the presence of KOC(CH
3)
3 in 2-propanol, leading to (
S)-1-phenylethanol with up to an enantiomeric excess (ee) of 67%.
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