Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

New Bifunctional Bis(azairidacycle) with Axial Chirality via Double Cyclometalation of 2,2’-Bis(aminomethyl)-1,1’-binaphthyl

Version 1 : Received: 31 January 2021 / Approved: 1 February 2021 / Online: 1 February 2021 (14:35:48 CET)

A peer-reviewed article of this Preprint also exists.

Sato, Y.; Kawata, Y.; Yasui, S.; Kayaki, Y.; Ikariya, T. New Bifunctional Bis(azairidacycle) with Axial Chirality via Double Cyclometalation of 2,2′-Bis(aminomethyl)-1,1′-Binaphthyl. Molecules 2021, 26, 1165. Sato, Y.; Kawata, Y.; Yasui, S.; Kayaki, Y.; Ikariya, T. New Bifunctional Bis(azairidacycle) with Axial Chirality via Double Cyclometalation of 2,2′-Bis(aminomethyl)-1,1′-Binaphthyl. Molecules 2021, 26, 1165.

Journal reference: Molecules 2021, 26, 1165
DOI: 10.3390/molecules26041165

Abstract

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 KBH4. The reaction of (S)-1 with an equimolar amount of [IrCl2Cp*]2 (Cp* = 5-C5(CH3)5) in the presence of sodium acetate in acetonitrile at 80 °C gave a diastereomeric mixture of new dinuclear dichloridodiiridium (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(CH3)3 to generate the corresponding 16e amidoiridium complex 6. The following hydrogen transfer from 2-propanol to 6 provided diastereomers of hydrido(amine)iridium with 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 catalyst ratio of 200 in the presence of KOC(CH3)3 in 2-propanol, leading to (S)-1-phenylethanol with up to 67% ee.

Subject Areas

bifunctional catalyst; metal-ligand cooperation; dinuclear complex; iridacycle; cyclometalation; asymmetric transfer hydrogenation; cyanation; 1,1-binaphthyl; axial chirality

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