Synthesis of chiral iridium complexes immobilized on amphiphilic polymers and their application to asymmetric catalysis

Abstract

This article details the enantioselective catalytic performance of crosslinked, polymer immobilized, Ir-based, chiral complexes for transfer hydrogenation of cyclic imines to chiral amines. Polymerization of the achiral vinyl monomer, divinylbenzene, and a polymerizable chiral 1,2-diamine monosulfonamide ligand followed by complexation with [IrCl 2 Cp*] 2 affords the crosslinked polymeric chiral complex, which can be successfully applied to asymmetric transfer hydrogenation of cyclic imines. Polymeric catalysts prepared from amphiphilic achiral monomers have high catalytic activity in the reaction and can be used both in organic solvents and water to give chiral cyclic amines with a high level of enantioselectivity (up to 98% ee). The asymmetric reaction allows for reuse of the heterogeneous catalyst without any loss in activity or enantioselectivity over several runs.

Mechanisms of Cobalt/Phosphine‐Catalyzed Cross‐Coupling Reactions

“…The phosphine ligands dppe, dppp, dpph, dppbz, as well as PPh 3 , the alkyl bromides R′Br (R′= n Pr, t Bu, n Dec), and styrene were purchased and used as received. The charge‐tagged styrene substrate (styr + )(BPh 4 − ) was synthesized according to reported procedures ,. CoCl 2 was dried at 523 K for 5 min in vacuo before use.…”

“…The chargetagged styrene substrate (styr + )(BPh 4 À )w as synthesized according to reported procedures. [32,33] CoCl 2 was dried at 523 Kf or 5min in vacuo before use. THF was dried over sodium/benzophenone and freshly distilled before use.…”

Chiral catalysts immobilized on achiral polymers: effect of the polymer support on the performance of the catalyst

“…: C 6 H 5 COCH 3 98% vs. 94% ee, C 6 H 5 COCH 2 CH 3 96 vs. 86% ee, p-Cl-C 6 H 4 COCH 3 99% vs. 91% ee, NaptCOCH 3 87% vs. 87% ee). 119,348 The effect of loading is crucial for the performance of many supported reagents and catalysts. In the case of the enantioselective reduction of acetophenone with a LAH derivative of the resin-bound ephedrine, enantioselectivity values ranged from 55% for a resin containing 2.1 mmol g À1 to 79% for a loading of 0.7 mmol g À1 .…”

Nickel-Catalyzed Asymmetric Hydrogenation of Cyclic Sulfamidate Imines: Efficient Synthesis of Chiral Cyclic Sulfamidates

“…For example, ring-opening reactions of chiral cyclic sulfamidates can offer convenient and efficient access to chiral amines, amino alcohols, amino acids, and their derivatives (Boulton et al., 1999, Wei and Lubell, 2000, Espino et al., 2001, Cohen and Halcomb, 2001, Cohen and Halcomb, 2002, Atfani et al., 2001, Nicolaou et al., 2002, Meléndez and Lubell, 2003, Ni et al., 2007, Rönnholm et al., 2007, Baig et al., 2010, Baig et al., 2011, Venkateswarlu et al., 2014, Albu et al., 2016, Su et al., 2016, Chen et al., 2014, Kong et al., 2015, Liu et al., 2017, Wu et al., 2018). So far the asymmetric catalytic synthetic methods of chiral cyclic sulfamidates were mainly focused on transition metal-catalyzed asymmetric intramolecular amidation of sulfamate esters (Liang et al., 2002, Liang et al., 2004, Fruit and Mueller, 2004, Zhang et al., 2005, Zalatan and Du Bois, 2008, Lin et al., 2008, Ichinose et al., 2011), additions of organoboron reagents to cyclic imines (Chen et al., 2014, Chen et al., 2018, Kong et al., 2015, Liu et al., 2017, Wu et al., 2018, Nishimura et al., 2012, Nishimura et al., 2013, Luo et al., 2012a, Luo et al., 2012b, Wang et al., 2013, Hepburn et al., 2013, Wang and Xu, 2013, Zhang et al., 2016a), and asymmetric reduction of cyclic ketimines (Wang et al., 2008, Yu et al., 2009, Kang et al., 2010, Lee et al., 2011, Lee et al., 2012, Han et al., 2011, Liu et al., 2019, Itsuno et al., 2014, Seo et al., 2015, Kim et al., 2018).…”