Noyori-Ikariya catalyst

Another organic polymer-supported version of the Noyori-Ikariya catalyst has been developed by attaching enantiomerically pure C2-symmetrical 1,2-diamines on chlorosulfonylated polystyrene under conditions preferentially leading to monosul-fonylation (Fig. 44) [127]. The obtained chiral functional resins were converted to the Ru(II) catalyst 149 and used in the TH of alkyl aryl ketones with FA-TEA azeotrope. Due to a high functionalisation level of catalytic resin, excellent activities and enantioselectivities were obtained with an S/C ratio as high as 150 the mean ee value of the resulting alcohols was 95 %, while conversions mostly reached 99 %. 

Zimbron, J. M. Dauphinais, M. Charette, A. B. Noyori-Ikariya catalyst supported on tetra-arylphosphonium salt for asymmetric transfer hydrogenation in water. Green Chem. 2015,17,3255-3259. 

Li, X. Wu, X. Chen, W Hancock, F. E. King, F. Xiao, J. Asymmetric transfer hydrogenation in water with a supported Noyori-Ikariya catalyst. Org. Lett. 2004, 6,3321-3324. 

Zhu, M. Effect of NH acidity on transfer hydrogenation of Noyori-Ikariya catalyst. Catal. Lett. 2016,1-5. 

Typically, heterogeneous transfer hydrogenations are carried out at higher temperatures. The Noyori-Ikariya ruthenium arene catalysts are stable up to temperatures around 80 °C, whilst the rhodium and iridium CATHy catalysts are... 

K.-J. Haack, S. Hashiguchi, A. Fujii, T. Ikariya, R. Noyori, The catalyst precursor, catalyst, and intermediate in the Ru(II)-promoted asymmetric hydrogen transfer between alcohols and ketones, Angew. Chem. Int. Ed. Engl., 1997, 36, 285-288. 

The mechanism of the catalysis (Scheme 20.8) is quite unlike that of the rhodium-DuPhos catalysis of prochiral olefins described above, since the ketone substrate does not bind to the metal (ruthenium) atom. When a substrate binds the metal, as in the rho-dium-DuPhos systems, there are opportnnities for unwanted pathways that terminate the catalysis. On the other hand, a conseqnence of the metal being protected by its ligands in the Noyori-Ikariya catalysis in principle rednces the likelihood of catalyst deactivation and increases the expectation for achieving very high catalyst utilization (substrate/catalyst ratios). Thus, in the asymmetric hydrogenation of acetophenone to (i )-l-phenylethanol, Noyori et al. reported an astounding molar snbstrate/catalyst ratio of 2,400,000 1. ... 

Scheme 1.42 Catalytic cycle for the trarrsfer hydrogenation of aromatic ketones by an active form of the Noyori-Ikariya (pre)catalyst 2 from early studies. Formation of the major enantiomeric product is shown. (Reprinted with permission from Dub, P. A. et al., Dalton Trans., 45, 6756-6781. Copyright 2016 Royal Society of Chemistry.)...

Stereoselection in the AH and ATH of aromatic ketones by the Noyori 1 and Noyori-Ikariya (pre)catalyst 2 takes place during the outer-sphere hydride transfer step, respectively. The N-H funchonality therefore not only stabilizes the corresponding transihon state via ionic N-H...O hydrogen-bonding interaction, but also orients the outer-sphere position of the substrate along the Ru-H-C axis making stereodifferenhation possible. 

The Noyori-Ikariya (pre)catalyst 2 or similar complexes exist as mixtures of two diastereomers originating from the relative configuration on the metal atom. For example, the real intermediate of the catalytic cycle, hydride complex RuH[(R, R)-N(Ts)CH(Ph)CH(Ph)NH2](ii -p-cymene) exists... 

Ikariya and Noyori et al. also reported the synthesis of new chiral Cp Rh and Cp Ir complexes (13 and 14) bearing chiral diamine ligands [(R,R)-TsCYDN and (R,R)-TsDPEN] (Scheme 5.10) these are isoelectronic with the chiral Ru complex mentioned above, and may be used as effective catalysts in the asymmetric transfer hydrogenation of aromatic ketones [42], The Cp Ir hydride complex [Cp IrH(R,R)-Tscydn] (14c) and 5-coordinated amide complex (14d), both of which would have an important role as catalytic intermediates, were also successfully prepared. 

The reaction of propargylic alcohols and sc C02 in the presence of a trialkylphosphine as a catalyst gave cyclic carbonates in an excellent yield (Ikariya and Noyori, 1999). Dixneuf reported that the reaction proceeded without solvent, but not in nonpolar solvents such as toluene. The reaction efficiency in sc C02 was superior to that in solution phase (Fournier et al., 1989 Journier et al., 1991). The TON reached 1200 and the TOF exceeded 400. The sufficient concentration of C02, as well as the high reactivity of the ion-pair intermediate in sc C02, is responsible for such high efficiency. 

Enantiopure alcohols can be produced using chiral hydrogenation catalysts for the reduction of ketones. A major breakthrough in this area was achieved in the mid-1980s by Takaya and Noyori, following the initial work of Ikariya s group... 

Carbon dioxide is a ubiquitous and environmentally benign compound. Several attempts have been made to use it as medium or as support for individual steps of the hydroformylation. The acidic properties of CO2 in solution have been advantageously employed to remove homogeneous catalysts with basic properties from the neutral organic reaction products (see Section A Posteriori Separation of Products and Catalysts ). BASF claimed supercritical carbon dioxide (SCCO2) for the extraction of the so-called heavy ends from low-boiling hydroformylation products and rhodium catalyst [55]. In recent years, also implementations of reactions in compressed carbon dioxide in supercritical or near-critical conditions have attracted particular attention [56]. A first review on the application of supercritical fluids (SFCs) in homogeneous catalysis was authored by Jessop, Ikariya, and Noyori in 1999 [57]. Later on, Leitner and Abraham [58,59] provided updates with special focus on the use of compressed carbon dioxide. 

Ikariya, T. Murata, K. Noyori, R. Bifunctional transition metal-based molecular catalysts for asymmetric syntheses. Org. Biomol. Chem. 2006, 4, 393-406. 

PG Jessop, Y Hsiao, T Ikariya, R Noyori. Catalytic production of dimethyhbr-mamide from supercritical carbon dioxide. J Am Chem Soc 116 8851-8852,1994. O Kocher, RA Koppel, A Baiker. Sol-gel derived hybrid materials as heterogeneous catalysts for the synthesis of N,N-dimethylformamide from supercritical carbon dioxide. Chem Commun 1996 1497-1498. 

---