Enantioselective catalysts for

Caller M, Hollis TK, Overman LE, Ziller J, Zipp GG (1997) First enantioselective catalyst for the rearrangement of allylic imidates to allylic amides. J Org Chem 62 1449-1456... 

Cohen F, Overman LE (1998) Planar-chiral cyclopalladated ferrocenyl amines and imines as enantioselective catalysts for allylic imidate rearrangements. Tetrahedron Asymmetry 9 3213-3222... 

Jautze S, Seiler P, Peters R (2007) Macrocyclic ferrocenyl-bisimidazoline palladacycle dimers as highly active and enantioselective catalysts for the Aza-Claisen rearrangement of Z-conflgured A-para-methoxyphenyl trifluoroacetimidates. Angew Chem Int Ed 46 ... 

The axially chiral 2,2 -bipyridine E is also an effective enantioselective catalyst for addition of allyltrichlorosilane to aldehydes.109... 

A further example of a reaction which may be optimised in IL/scC02 by selection of the appropriate anion for the IL is catalytic enantioselective hydrovinylation, a synthetically interesting and truly atom economic C-C bond forming reaction [77-79]. The nickel complex below has been developed by Wilke and co-workers as precursor for a highly active and enantioselective catalyst for this process. 

DM-BIPHEP, a conformationally flexible diphosphine, exists as an equilibrium mixture of the R and S isomers (Fig. 32.50) [141]. Addition of an equimolar amount of (S,S)-DPEN to RuCl2(dm-biphep)(dmf) forms a 3 1 mixture of (S)-DM-BIPHEP/(S,S)-DPEN-RuC12 complex and the R,SS diastereoisomer. The major S,SS complex gives a more active and enantioselective catalyst for the hydro-... 

Chiral amines were always considered important targets for synthetic chemists, and attempts to prepare such compounds enantioselectively date back to quite early times. Selected milestones for the development of enantioselective catalysts for the reduction of C = N functions are listed in Table 34.1. At first, only heterogeneous hydrogenation catalysts such as Pt black, Pd/C or Raney nickel were applied. These were modified with chiral auxiliaries in the hope that some induction - that is, transfer of chirality from the auxiliary to the reactant -might occur. These efforts were undertaken on a purely empirical basis, without any understanding of what might influence the desired selectivity. Only very few substrate types were studied and, not surprisingly, enantioselectivities were... 

After some mechanistic studies showing that the reduction of N,0-acetals proceeds via a prochiral iminium cation, Bomer et al. aimed at finding an enantioselective catalyst for this transformation by preparing a library of 144 catalysts... 

To develop effective enantioselective catalysts for asymmetric hydrogenation, the research groups in this area have fully investigated the factors controlling the OY (Figure 14.5). 

Covalent attachment chiral Co(salen) complexes to polystyrene and silica gave efficient and highly enantioselective catalysts for the hydrolytic kinetic resolution (HKR) of terminal epoxides, including epichlorohydrin. These systems provide practical solutions to difficulties with the isolation of reaction products from the HKR. Removal of the supported catalyst by filtration and repeated recycling was demonstrated with no loss of reactivity or enantioselectivity. The immobilised catalysts have been adapted to a... 

Pure Sji,Rc)-9 is a highly enantioselective catalyst for the DC reaction between methacrylonitrile and nitrones IV and V, but only stoichiometric amounts of the... 

The Catalysis Concept of Iminium Activation In 2000, the MacMillan laboratory disclosed a new strategy for asymmetric synthesis based on the capacity of chiral amines to function as enantioselective catalysts for a range of transformations that traditionally use Lewis acids. This catalytic concept was founded on the mechanistic postulate that the reversible formation of iminium ions from a,p-unsaturated aldehydes and amines [Eq. (11.10)] might emulate the equilibrium dynamics and 7i-orbital electronics that are inherent to Lewis acid catalysis [i.e., lowest unoccupied molecular orbital (LUMO)-lowering activation] [Eq. (11.9)] ... 

In addition to the enantioselective epoxidation of trans- and trisnbstitnted olefins, efforts have also been made for the asymmetric epoxidation of cis- and terminal olefins. Glncose-derived ketone 55 was reported to be a highly enantioselective catalyst for the epoxidation of varions cw-olefins and certain terminal olefins (Fig. 11, Table 4) [97-100]. The resnlts of epoxidation with ketone 55 indicate that a n... 

Kim et al. have developed a practical procedure for the DKR of primary amines illustrated by substrate 56c (Scheme 2.28). They employed a supported palladium nanocatalyst as the racemization catalyst and commercially available CALB as the enantioselective catalyst for acylation of the amine using ethyl methoxyacetate as the acyl donor. High yields and enantiomeric excesses were achieved [30]. 

The formation of 1-deuterio primary alcohols, such as (S)-8 from achiral aldehydes with catecholborane-d in the presence of an enantioselective catalyst (for configurational assignment, see p 453)76. 

It was clear that 1 would be derived from a Diels-Alder adduct. There has been a great deal of work in recent years around the development of enantioselective catalysts for the Diels-Alder reaction, but the catalysts that have been developed to date only work with activated dienophile-diene combinations. For less reactive dienes, it is still necessary to use chiral auxiliary control. One of the more effective of those was the known camphor-derived tertiary alcohol, so that was used in this project. Diels-Alder cycloaddition of the diene 4 with the enantiomerically-pure enone 5 led to the adduct 6 with high diastereocontrol. Oxidative cleavage led to the acid 7, which was carried on to the bis-enone I. 

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