Nishiyama catalyst

A key factor in our case was to limit the amount of cis-isomer formed as a byproduct. Thus, based on overall performance the Nishiyama catalyst 27 was chosen for further development. Implementation of this chemistry did require, however, several modifications to allow for scale-up. For example ... 

Fig. 10 Preparation of 1 via the asymmetric cyclopropanation route. Route D (a) EDA, 2 mol-% Nishiyama catalyst 27, toluene (b) NaOH, TBAH (c) dehydroabeityl amine,...

Asymmetric epoxidation of olefins with ruthenium catalysts based either on chiral porphyrins or on pyridine-2,6-bisoxazoline (pybox) ligands has been reported (Scheme 6.21). Berkessel et al. reported that catalysts 27 and 28 were efficient catalysts for the enantioselective epoxidation of aryl-substituted olefins (Table 6.10) [139]. Enantioselectivities of up to 83% were obtained in the epoxidation of 1,2-dihydronaphthalene with catalyst 28 and 2,6-DCPNO. Simple olefins such as oct-l-ene reacted poorly and gave epoxides with low enantioselectivity. The use of pybox ligands in ruthenium-catalyzed asymmetric epoxidations was first reported by Nishiyama et al., who used catalyst 30 in combination with iodosyl benzene, bisacetoxyiodo benzene [PhI(OAc)2], or TBHP for the oxidation of trons-stilbene [140], In their best result, with PhI(OAc)2 as oxidant, they obtained trons-stilbene oxide in 80% yield and with 63% ee. More recently, Beller and coworkers have reexamined this catalytic system, finding that asymmetric epoxidations could be perfonned with ruthenium catalysts 29 and 30 and 30% aqueous hydrogen peroxide (Table 6.11) [141]. Development of the pybox ligand provided ruthenium complex 31, which turned out to be the most efficient catalyst for asymmetric... 

Negishi E, Tan Z (2005) Diastereoselective, Enantioselective, and Regioselective Carbo-alumination Reactions Catalyzed by Zirconocene Derivatives. 8 139-176 Netherton M, Fu GC (2005)Pa]ladium-catalyzed Cross-Coupling Reactions of Unactivated Alkyl Electrophiles with Organometallic Compounds. 14 85-108 Nicolaou KC, King NP, He Y (1998) Ring-Closing Metathesis in the Synthesis of EpothUones and Polyether Natmal Products. 1 73-104 Nishiyama H (2004) Cyclopropanation with Ruthenium Catalysts. 11 81-92 Noels A, Demonceau A, Delaude L (2004) Ruthenium Promoted Catalysed Radical Processes toward Fine Chemistry. 11 155-171... 

As an example of the selective removal of products, Foley et al. [36] anticipated a selective formation of dimethylamine over a catalyst coated with a carbon molecular sieve layer. Nishiyama et al. [37] demonstrated the concept of the selective removal of products. A silica-alumina catalyst coated with a silicalite membrane was used for disproportionation and alkylation of toluene to produce p-xylene. The product fraction of p-xylene in xylene isomers (para-selectivity) for the silicalite-coated catalyst largely exceeded the equilibrium value of about 22%. 

Nishiyama et al. introduced a new catalyst, the chiral tr<2 i -RuCl2(Pybox-i-Pr)(ethylene) complex (91), which showed for the first time both enantio- and diastereoselectivity (trans-selectivity) at excellent levels in the reactions of terminal olefins (Scheme 66).251-253 With 4-substituted Ru(Pybox-i-Pr) complexes (92), they studied the substituent effect on enantioselectivity... 

I0 lnterrupted-temperature programmed desorption of hydrogen over silica-supported platinum catalysts, Arai, M., Fukushima, M., Nishiyama, Y., Applied Surf. Sci., vol. 99, no. 2, pp. 145-150, 1996. 

Nicolaou KC, King NP, He Y (1998) Ring-Closing Metathesis in the Synthesis of Epothilones and Polyether Natimal Products. 1 73-104 Nishiyama H (2004) Cyclopropanation with Ruthenium Catalysts. 11 81-92 Nobis M, see Hugl H (2008) 23 1-17... 

A. Endoh, K. Nishiyama, K. Tsutsumi, T. Takaishi, Zeolites as Catalysts, Sorbents and Detergent Builders(Stud. Surf. Sci. Catal., 46), Elsevier, Amsterdam, 1989, p.779. 

The C2-symmetric 2,6-bis(2-oxazolin-2-yl)pyridine (pybox) ligand was originally applied with Rh for enantioselective hydrosilylation of ketones [79], but Nishiyama, Itoh, and co-workers have used the chiral pybox ligands with Ru(II) as an effective cyclopropanation catalyst 31 [80]. The advantages in the use of this catalyst are the high enantiocontrol in product formation (>95 % ee) and the exceptional diastereocontrol for production of the trans-cyclopropane isomer (>92 8) in reactions of diazoacetates with monosubstituted olefins. Electronic influences from 4-substituents of pyridine in 31 affect relative reactivity (p = +1.53) and enantioselectivity, but not diastereoselectivity [81]. The disadvantage in the use of these catalysts, at least for synthetic purposes, is their sluggish reactivity. In fact, the stability of the intermediate metal carbene has allowed their isolation in two cases [82]. 

Scheme 4.27 Asymmetric hydrosilylation of ketone 66 with iron catalysts according to Nishiyama and Furuta [59],...

Davies and co-workers have explored the role of ligand conformation in the ruthenium(II)-catalyzed cyclopropanation of styrene.10 This study was based on results reported by Nishiyama in which the catalyst prepared in situ from pyridine-bis(oxazoline) 62 and RuCI2(/>cymene) 2 was found to be highly active and selective in the reaction of ethyl diazoacetate with styrene (66% yield, 84% de, and 89% ee of major trans-isomer).52 Several ligands hindered on the oxazoline ring, including 3, were tested and poorer yields and selectivities were obtained (for 3, 50% yield, 81% de, and 59.5% ee of major trans-isomer), which indicated unfavorable steric interactions between styrene and the Ru(in-pybox) carbene complex (Scheme 17.22).10... 

In 1994, asymmetric cydopropanation (ACP) with ruthenium catalysts was first reported by Nishiyama and coworkers [ 19,20] by adoption of their chiral bis(oxazolinyl)pyridine (Pybox) ligands. The reaction profiles of Ru Pybox catalysts reveal extremely high trans selectivity with high enantioselectivity (or di-astereoselectivity) of cyclopropane products at the relatively low reaction temperatures (around 20-50 °C) so far reported for ruthenium catalysts. After 1997,... 

The effectiveness of various substituted BINOL ligands 12-16 in the Zr(IV)-or Ti(IV)-catalyzed enantioselective addition of allyltributyltin to aldehydes was also investigated by Spada and Umani-Ronchi [21], The number of noteworthy examples of asymmetric allylation of carbonyl compounds utilizing optically active catalysts of late transition metal complexes has increased since 1999. Chiral bis(oxazolinyl)phenyl rhodium(III) complex 17, developed by Mo-toyama and Nishiyama, is an air-stable and water-tolerant asymmetric Lewis acid catalyst [23,24]. Condensation of allylic stannanes with aldehydes under the influence of this catalyst results in formation of nonracemic allylated adducts with up to 80% ee (Scheme 3). In the case of the 2-butenyl addition reac-... 

The catalyst was introduced with other oxidants H. Nishiyama, T. Shimada, H. Itoh, H. Sugiyama, Y. Motoyama, Chem. Commun. 1997, 1863. 

Other Hgands are useful in the C-N bond coupling of aryl bromides and cyclic amines. In 1998, Nishiyama and co-workers at Tosoh corporation reported that tri-ferf-butylphosphine is an effective supporting hgand for the palladium-catalyzed arylation of piperazine [36]. The (f-Bu)3P/Pd-catalyst provided the product with 1 mol% Pd in high selectivity, Eq. (11). 

Nishiyama, and co-workers first reported that the catalyst derived from Pd(OAc)2 and (f-Bu)3P effects the C-N bond formation to produce triarylamines in excellent yield [65]. This system also is useful in the coupling of diarylamines and aryl chlorides. Hartwig and co-workers found this protocol optimal for the preparation of triarylamines. The (f-Bu)3P/Pd-catalyst was sufficiently active such that the coupfing of diarylamines and aryl bromides can be performed at room temperature,Eq. (34) [50]. The (f-Bu)3P/Pd-system has been used to produce new triarylamine-based polymers [ 64 a - d]. 

Nishiyama, Yamamoto, and Koie also reported that the (f-Bu)3P/Pd-based catalyst is effective in the C-N bond forming reaction between an aryl iodide as well as an aryl bromide and piperazine [36]. 

Reddy and Tanaka reported that (Cy3P)2PdCl2 catalyzes the coupling of secondary amines with aryl chlorides, Eq. (41) [71]. With this catalyst system based on the use of sterically hindered, electron-rich trialkylphosphines, electron-poor and electronically neutral aryl halides were reacted at elevated temperatures. Similarly, Nishiyama, Yamamoto and Koie reported the formation of an arylpiperazine from chlorobenzene using a (t-Bu)3P/Pd catalyst [36]. 

H. Ohkita, R. Nishiyama, Y. Tochihara, T. Mizushima, N. Kakuta, Y. Morioka, A. Ueno, Y. Namiki, S. Tanifuji, H. Katoh, H. Sunazuka, R. Nakayama, and T. Kuroyanagi, Acid Properties of Silica-Alumina Catalysts and Catalytic Degradation of Polyethylene, Ind. Eng. Chem. Res., 32, 3112-3116 (1993). 

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