Noyori coupling

These transition-metal catalysts contain electronically coupled hydridic and acidic hydrogen atoms that are transferred to a polar unsaturated species under mild conditions. The first such catalyst was Shvo s diruthenium hydride complex reported in the mid 1980s [41 14], Noyori and Ikatiya developed chiral ruthenium catalysts showing excellent enantioselectivity in the hydrogenation of ketones [45,46]. 

Scheme 2.6 Late generation synthesis of desoxy epothilone B and epothilone B. The key steps in this total synthesis are a stereospecific aldol reaction, B-alkyl Suzuki coupling, and stereoselective Noyori reaction.

Example 5 Hayakawa and Noyori group in their studies on new activators for phosphoroamidite coupling reactions have applied the most effective member of the group of acid/azole complexes AT-(phenyl)imidazolium tri-flate (N-PhIMT) in the efficient synthesis of biologically important compounds [20j]. A noteworthy example is synthesis of cytidine-5 -monophos-pho-AT-acetylneuraminic acid. This compound is a source of sialic acid in the sialyltransferase-catalysed biosynthesis of sialyl oligosaccharides [25]. 

R. Noyori, M. Suzuki, New synthetic methods. (49). Prostaglandin syntheses by three-component coupling, Angew. Chem. Int. Ed. Engl. 23 (1984) 847. 

UMukaiyama Hayashi Chem. Lett. 1974,15 Mukaiyama Kobayashi Murakami Chem. Lett. 1984,1759 Murata Suzuki Noyori Tetrahedron 1988, 44, 4259. For a review of cross-coupling reactions of acetals, sec Mukaiyama Murakami Synthesis 1987, 1043-1054. 

Suzuki, M. Morita, Y. Koyano, H. Koga, M. Noyori, R. Three-Component Coupling Synthesis of Prostaglandins. A Simplified, General Procedure, Tetrahedron 1990,46,4809. 

In the early 1990s, Smith and co-workers reported on the total synthesis of the antitumor antibiotic macrolactam (+)-hitachimycin 35 (Figure 12.1) using a Noyori three-component coupling to assemble the polysubstituted cyclopentane unit [24]. 

This is mainly due to the fact that by means of chiral ligands it is comparatively facile to transfer absolute stereochemical information to a cat-alytically active metal center. However, the success of some of these reactions (e.g. the Sharpless asymmetric epoxidation or the Noyori hydrogenation) must not hide the fact that the number of powerful transition metal-catalyzed C-C coupling reactions, which proceed reliably with high enantioselectivity, is still rather small. 

The ultimate in the three-component coupling approach to prostaglandins has now been achieved by Noyori (48). As illustrated in Fig. 15, the cuprate derived from iodide [82] was added to enone [80] in the usual fashion. Then, after addition of hexamethylphosphoramide, triphenyltin chloride was used to effect enolate interchange. As opposed to lithium (or copper) enolates, the tin enolate is cleanly alkylated with allylic iodide [81]. The protected PGE2 [83] was obtained in 78% yield. Two-step deprotection to PGEj was straightforward. 

Punaglandin 4 (PUG 4, 151, Figure 6.10) is one of the chlorinated marine prostanoids isolated from a Hawaiian octocoral, Telesto riisei, by Scheuer and coworkers in 1985. Its remarkable antitumor activity coupled with its unique structure attracted the attention of chemists, and its synthesis was achieved by Yamada, Noyori, Shibasaki, and Mori s groups. Our synthesis relied on lipase-catalysed asymmetric process, and is summarized in Figures 6.10 and 6.11.12... 

Curve A in Scheme 6, represents an example of the asymmetric ampHfication obtained by Noyori et al. [12], which still remains the highest (-i-)-NLE known. The authors found that the reaction is first-order with respect to the catalyst and that the asymmetric ampHfication originates from the accumulation of unreactive meso-dimers of the zinc alcoholate of (-)-DAIB. The (-l-)-NLE maybe seen as the consequence of a reservoir, weakly coupled to the catalytic cycle and storing some racemic Hgand. 

Yanagisawa S, Sudo T, Noyori R, Itami K (2008) Direct coupling of arenes and iodoarenes catalyzed by a rhodium complex with a strongly tc-accepting phosphite ligand. Tetrahedron... 

An alternative route by the Danishefsky group was developed [142e-g] (Scheme 84). The aldol reaction of ethyl ketone 580, prepared from P-keto ester 579, with aldehyde 581 stereoselectively afforded 582 (dr = 5.4 1). After Troc protection followed by hydrolysis of the enol ether, Suzuki coupling with 583 followed by TBS deprotection gave the desired (12Z)-olefin 584. The Noyori reduction of the P-keto ester 584 gave 3a-alcohol with high stereoselectivity, which was converted into hydroxy carboxylic acid 585. Macrolactonization of 585 was accomplished by the Yamaguchi method, and subsequent deprotection and DMDO oxidation efficiently afforded epothilone B (5b). 

Troponoids (5, 222-223). The reaction of a,a -dibromo ketones with diiron nonacarbonyl to generate an oxyallyl-Fe(II) species originally suffered one limitation only secondary and tertiary dibromo ketones reacted satisfactorily. For example, reaction of a,a -dibromoacetone, BrCH2COCH2Br, fails. Noyori et al. have presented a solution to this limitation. The reaction is carried out with a polybromo ketone and the bromine atoms in the adduct are removed with Zn-Cu couple. The synthesis of 8-oxabicyclo[3.2.11oct-6-ene-3-one (1) is... 

A new general approach to the synthesis of C-glycosidic compounds and C-nucleosides was elaborated by Noyori. In his approach the starting material, unsaturated bicyclic ketone 236, was prepared in a cyclocoupling reaction between 1,1,3,3-tetrabromoacetone and furan, followed by a zinc-copper couple... 

---