Chiral hydrogenation

Chips, semiconductor Chiral additives Chiral-AGP Chiral auxiliaries Chiral crown ethers Chiral hydrogenation Chirality... 

Keywords a-Hydroxylated lignans Natural product synthesis Enantioselective hydrogenation Chiral building blocks Malic acid... 

Chiral hydrogenation catalysts. Rhodium and ruthenium phosphines are effective homogeneous catalysts for hydrogenation. Chiral ligands can be attached to accomplish asymmetric induction, the creation of a new asymmetric carbon as mostly one enantiomer. 

Homogeneous catalytic hydrosilation of polar multiple bonds such as C=0 and C=N bonds is a useful synthetic tool as a better substitute for catalytic hydrogenation. Chiral rhodium complexes are employed for the asymmetric reduction of ketones (eq(32)) [29]. 

A-Boc pyrroles are subject to partial or complete reduction. With a Ru complex and 2,2 -bis(l-diphenylphosphinoethyl)-l,l -biferrocenyl ligand to effect hydrogenation chiral pyrrolidines are S3mthesized. ... 

An interesting application of these catalysts is for asymmetric addition of the elements of hydrogen. Chiral catalysts are synthesized by use of optically active phosphine ligands. This constitutes a very efficient way of generating centers of... 

Gladiali, S., Alberico, E. (2006). Asymmetric transfer hydrogenation chiral ligands and applications. Chemical Social Reviews, 35,226—236. http //dx.doi.org/10.1039/B513396C. 

In the area of asymmetric hydrogenation chiral dighosphines have played a center role since and many applications have been developed. Important new ligands that have been introduced comprise Noyori s BINAP [28], DuPhos (Burk) [29], Takaya s BINAPHOS [30], and Ci-symmetric ferrocene-based ligands introduced by Togni [31]. Industrial products, of which the synthesis uses enantioselective phosphine-derived metal-catalysts are for instance menthol, metolachlor, biotin, and several alcohols, e.g. (R)-1,2-propanedioI, For details about the applications the reader is referred to reviews and references therein [32, 33]. Substituents and backbones have an enormous influence on the performance of the ligands, but usually rationalizations are lacking. 

Keywords Ketones Asymmetric transfer hydrogenation Chiral metal catalysts Recyclable catalysts Transfer hydrogenation in water... 

Gladiali, S. Alberico, E. Asymmetric transfer hydrogenation Chiral ligands and applications. Chem. Soc. Rev. 2006,35, 226-236. 

Other reactions described, with varying degrees of success, have been chiral epoxidation, chiral hydrogenation, chiral iodination, and chiral reduction of keto-groups. One of the last reactions is especially interesting in using a chiral phase-transfer catalyst. Finally, Johnson and his co-workers have reported in full the asymmetric induction in their steroid synthesis via polyene cyclization [e.g. (46) (47) with ca. 90 % optical purity]. ... 

Brintzinger s catalyst systems [C2H4(Ind-H4)2ZrX2]/MAO act as hydrogenation rather than polymerization catalysts if excess H2 is present (20 bar) internal and disubstituted olefins are only hydrogenated. Chiral catalysts give up to 36% ee. Comparison of the stereoisomers of 1-pentene dimerization and deuteration indicate that opposite enantiofaces of the incoming olefin are preferred in the two reaction types, apparently because of the need to accomodate the metal-bound alkyl chain in the polymerization case in the... 

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