Copper asymmetric nucleophilic allylic

Kanai and colleagues developed an enantioselective synthesis of various 2-(2-hydroxyethyl)indole scaffolds via the amido-cupration of allenes followed by the asymmetric addition of carbonyl compounds. Treatment of allene 88 with a copper catalyst forms a stable and highly nucleophilic allyl-copper species, which then adds into benzaldehyde (89) to furnish indole 90. A range of carbonyl compounds are competent in the sequence, including aryl- and heteroaryl aldehydes, alkyl aldehydes, and aryl ketones. This is reported to be the first example of a combined catalytic indole generation and subsequent enantioselective addition of carbonyl compormds (14CS1585). 

Several catalytic asymmetric allylation reactions have been developed specifically for iminoester derivatives, but the level of enantioselection remains typically only in the lowto high 80s (Table 1.15). Allylstannanes [99], allylsilanes [100], allyltrimethox ysilanes [101], and allylboronates [102] are suitable nucleophiles in these copper or zinc catalyzed processes. 

A bidentate N-heterocyclic carbene (NHC) ligand was found to be efficient for the asymmetric allylic alleviation employing diethylzinc (Scheme 15.22). In the reaction, a binuclear silver complex undergoes facile ligand exchange with a copper salt to afford an effective copper catalyst. y-Selective allylic alleviation is realised with allevlboranes as nucleophiles that are easily... 

The direct access to a-chiral allylic boronates and silanes [9] from linear precursors by copper(l)-catalyzed asymmetric allylic displacement with boron and silicon nucleophiles is another major focus of this chapter. A separate section is devoted to direct enantioconvergent transformations of racemic allylic acceptors. 

Independent from the work of Oestreich and co-workers, the group of Shintani and Hayashi presented another example of NHC-copper(I)-catalyzed asymmetric allylic substitution of allylic phosphates by nucleophilic silicon (Scheme 28) [61]. The NHC precursor L23 in combination with CuCl and NaOH as base allowed for the enantioselective preparation of several a-chiral allylic silanes. The choice of base is cmcial as aUcoxides had a negative effect on the regioselectivity (not... 

On the basis of this finding, Shibasaki s group developed a series of asymmetric reactions using soft copper(I) Brpnsted base catalysts and a wide variety of pre-nucleophiles (thioamides [34 3], isocyanide [44, 45], unsaturated butyrolactones [46, 47], nitroalkanes [48], allyl cyanide [49, 50], and a-trifluoromethylacetamide [51]) via proton transfer strategy (Fig. 5). 

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