Ruthenium catalyzed asymmetric hydrogenation

Other enantioselective reactions performed by microwave heating include asymmetric Heck reactions (Scheme 6.53 a) [109] and ruthenium-catalyzed asymmetric hydrogen-transfer processes (Scheme 6.53 b) [110]. 

Modification of the electronic and steric properties of BINAP, BIPHEMP, and MeO-BI-PHEP led to the development of new efficient atropisomeric ligands. Although most of them are efficient for ruthenium-catalyzed asymmetric hydrogenation [3], Zhang et al. have recently reported an ortho-substituted BIPHEP ligand, o-Ph-HexaMeO-BIPHEP, for the rhodium-catalyzed asymmetric hydrogenation of cyclic enamides (Scheme 1.2) [31]. 

BINAP core-functionalized dendrimers were synthesized by Fan et al. (36), via condensation of Frechet s polybenzyl ether dendritic wedges to 5,5 -diamino-BINAP (26—28). The various generations of BINAP core-functionalized dendrimers were tested in the ruthenium-catalyzed asymmetric hydrogenation of 2-[p-(2-methyl-propyl)phenyl]acrylic acid in the presence of 80 bar H2 pressure and in a 1 1 (v/v) methanol/toluene mixture. As later generations of the in situ prepared cymeneruthe-nium chloride dendritic catalysts were used, higher activities were observed (TOF values were 6.5, 8.3, and 214 h respectively). Relative to those of the BINAP... 

Ruthenium-Catalyzed Asymmetric Hydrogenation of Aromatic Ketones... 

Kuwano, R. and Kashiwahara, M. Ruthenium-catalyzed Asymmetric Hydrogenation of N-Boc-Indoles. Org. Lett. 2006, 8, 2653-2655. 

BTNAP is available as either the (+)- or (- )-enaiitionier and displays broad utility in rhodium- and ruthenium-catalyzed asymmetric hydrogenations of (3-keto esters and alkenes. ... 

Girard, C., Genet, J.-P., Bulliard, M. Non-linear effects in ruthenium-catalyzed asymmetric hydrogenation with atropisomeric diphosphines. Eur. J. Org. Chem. 1999, 2937-2942. 

Scheme 6.15 Ruthenium catalyzed asymmetric hydrogenation of pyrrolidinium salts.

The above catalytic systems for the asymmetric hydrogenation of quinolines are mainly iridium catalysts. In 2008, Fan and coworkers developed recyclable phos phine free chiral cationic ruthenium catalyzed asymmetric hydrogenation of qui nolines [23]. They found that the phosphine free cationic Ru/TsDPEN catalyst exhibited unprecedented reactivity and high enantioselectivity in the hydrogenation of quinolines in neat ionic liquid. The results were very excellent and enantioselec... 

Gelpke, A.E.S., Kooijman, H., Spek, A.L. and Hiemstra, H., Synthesis of the dibenzofuran based diphosphine ligand BIFAP and its water-soluble derivative BIFAPS and their use in ruthenium catalyzed asymmetric hydrogenation, Chem. Ear J., 1999, 5, 2472. 

Dynamic Kinetic Resolution (DKR) under Hydrogenation Conditions Ruthenium-catalyzed asymmetric hydrogenation of racemic a-substituted ketones via-dynamic kinetic resolution (DKR) is one of the elegant and powerful methods for the synthesis of chiral alcohols that simultaneously control two adjacent stereogenic centers with high levels of selectivity in a single chemical operation. This method was first reported... 

Liu S, Xie J-H, Li W, Kong W-L, Wang L-X, Zhou Q-L. Highly enantioselective synthesis of chiral cyclic amino alcohols and conhydrine hy ruthenium-catalyzed asymmetric hydrogenation. Org. Lett. 2009 ll(21) 4994-4997. 

Mordant C, Reymond S, Tone H, Lavergne D, Touati R, Ben Hassine B, Ratovelomanana-Vidal V, Genet J-P. Total synthesis of dolastatin 10 through ruthenium-catalyzed asymmetric hydrogenations. Tetrahedron 2007 63(27) 6115-6123. 

Phansavath P, Duprat de Paule S, Ratovelomanana-Vidal V, Genet J-P. An efficient formal synthesis of (—) balanol by using ruthenium-catalyzed asymmetric hydrogenation. Eur. J. Org. Chem. 2000 (23) 3903-3907. 

Figure 4.35 Chiral BINAP-functionalized Janus dendrimers for the ruthenium-catalyzed asymmetric hydrogenation.

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