Chiral ligand asymmetrical synthesis

Enantioselective addition of dialkylzincs to imines using chiral ligands asymmetric synthesis of optically active amines... 

Tomioka, K., Satoh, M., Taniyama, D., Kanai, M., and lida, A. (1998) Enantioselective addition of thiazolyllithium to aldimines with the aid of chiral ligand - asymmetric synthesis of (S)-Doe, a component of marine natural product, dolastatin. Heterocycles, 47, 77-80. 

Sharpless asymmetric aminohydroxylation can also be used for taxol side chain synthesis. For example, using DHQ as a chiral ligand, asymmetric aminohydroxylation of methyl trau.v-cinnamatc provides compound 240 in high enantiomeric excess (Scheme 7-80).37... 

Keywords Chiral catalysts. Asymmetric synthesis. High-throughput screening, Ligand diversity, Solid phase chemistry... 

In the presence of a chiral ligand, asymmetric Heck reactions can be carried out. The axially-chiral bisphosphine ligand (/ )- or (5)-BINAP promotes good to excellent levels of enantioselectivity in intramolecular Heck reactions. For example, insertion of palladium into the aryl iodide 214 followed by cyclization gave the indolinone 215 in high enantiomeric excess, used in a synthesis of physostigmine (1.215). ... 

New catalytic systems are being continually introduced into organic chemistry. In particular, more and more catalytic applications are directed towards the use of chiral ligands, the synthesis of optically active compounds being a constant challenge for the pharmaceutical industry. In the latter area, the discovery of the nonlinear effect in asymmetric catalysis by Kagan represented a particularly important breakthrough. 

Asymmetric cyclization using chiral ligands has been studied. After early attempts[142-144], satisfactory optical yields have been obtained. The hexahy-dropyrrolo[2,3-6]indole 176 has been constructed by the intramolecular Heck reaction and hydroaryiation[145]. The asymmetric cyclization of the enamide 174 using (S j-BINAP affords predominantly (98 2) the ( )-enoxysilane stereoisomer of the oxindole product, hydrolysis of which provides the ( l-oxindole aldehyde 175 in 84% yield and 95% ec. and total synthesis of (-)-physostig-mine (176) has been achieved[146]. 

Simple esters cannot be allylated with allyl acetates, but the Schiff base 109 derived from o -amino acid esters such as glycine or alanine is allylated with allyl acetate. In this way. the o-allyl-a-amino acid 110 can be prepared after hydrolysis[34]. The Q-allyl-o-aminophosphonate 112 is prepared by allylation of the Schiff base 111 of diethyl aminomethylphosphonates. [35,36]. Asymmetric synthesis in this reaction using the (+ )-A, jV-dicyclohex-ylsulfamoylisobornyl alcohol ester of glycine and DIOP as a chiral ligand achieved 99% ec[72]. 

Efficient enantioselective asymmetric hydrogenation of prochiral ketones and olefins has been accompHshed under mild reaction conditions at low (0.01— 0.001 mol %) catalyst concentrations using rhodium catalysts containing chiral ligands (140,141). Practical synthesis of several optically active natural... 

Stereoselective asymmetric synthesis with participation of diazocarbonyl intermediates in the presence of catalysts possessing chiral heterocyclic ligands 97CC983. 

Chiral carbenoid complexes with 2,2 -bipyridine ligands for asymmetric synthesis 98YGK764. 

Mukaiyama, T., and Asami, A. Chiral Pyrrolidine Diamines as Efficient Ligands in Asymmetric Synthesis. 127,133-167(1985). 

The Rh2(DOSP)4 catalysts (6b) of Davies have proven to be remarkably effective for highly enantioselective cydopropanation reactions of aryl- and vinyl-diazoacetates [2]. The discovery that enantiocontrol could be enhanced when reactions were performed in pentane [35] added advantages that could be attributed to the solvent-directed orientation of chiral attachments of the ligand carboxylates [59]. In addition to the synthesis of (+)-sertraline (1) [6], the uses of this methodology have been extended to the construction of cyclopropane amino acids (Eq. 3) [35], the synthesis of tricyclic systems such as 22 (Eq. 4) [60], and, as an example of tandem cyclopropanation-Cope rearrangement, an efficient asymmetric synthesis of epi-tremulane 23 (Eq. 5) [61]. 

Arai Y., Koizumi T. Synthesis and Asymmetric Diels-Alder Reactions of Chiral. Alpha.,.Beta.-Unsaturated Sulfoxides Bearing a 2-Exo-Hydroxy-lO-Bornyl Group As an Efficient Ligand on the Sulfur Center Rev. Heteroat. Chem. 1992 6 202-217 Keywords allenic sulfoxide, a-sulfinylmaleate, a-sulfinylmaleimide, asymmetric synthesis, chiral unsaturated sulfoxides... 

Kagan HB (1985) Chiral ligands for asymmetric catalysis. In Morrison JD (ed) Asymmetric synthesis, vol 5. Academic Press, New York, chap 1... 

More recently, a very efficient asymmetric carbolithiation of N,N-dimethyl-aminofulvene 30, leading to a chiral cyclopentadienide anion, was reported by Hayashi et al. [6] for the synthesis of chiral metallocenes (Scheme 6). By adding an aryl lithium such as 31 complexed with a chiral ligand on fulvene 30, a cyclopentadienide ion 32 bearing a stereogenic center at the a position was generated. This anion was reacted with [RhCl(nbd)]2 to yield... 

---