Ketones allyltributylstannane

While selective reaction of aldehydes takes place with the typical Lewis acids TiCL, SnCl4, TMSOTf, etc., lanthanide triflates [Ln(OTf)3] are unique Lewis acids that change the reaction course dramatically aldimine reacts selectively in the coexistence of aldehydes [70]. Among a series of Ln(OTf)3 tested, Yb(OTf)3 exhibited the most prominent chemoselectivity in addition to high chemical yields. The silyl enol ethers of ketones, allyltributylstannane and Me3SiCN are all applicable as chemoselective nucleophiles (Table 2-9). Preferential formation of Yb(OTf)3-aldimine complexes was postulated by C NMR spectral analysis in the presence of PhCHO and Y-benzylideneaniline. 

The enantioselective addition of allyltributylstannanes to aldehydes and ketones has been performed in the presence of various chiral indium(III) complexes derived from (R)-BINOL,136 (S )-BINOL,137,138 and PYBOX.139,140... 

Nevertheless, the use of chirally modified Lewis acids as catalysts for enantioselective aminoalkylation reactions proved to be an extraordinary fertile research area [3b-d, 16]. Meanwhile, numerous publications demonstrate their exceptional potential for the activation and chiral modification of Mannich reagents (generally imino compounds). In this way, not only HCN or its synthetic equivalents but also various other nucleophiles could be ami-noalkylated asymmetrically (e.g., trimethylsilyl enol ethers derived from esters or ketones, alkenes, allyltributylstannane, allyltrimethylsilanes, and ketones). This way efficient routes for the enantioselective synthesis of a variety of valuable synthetic building blocks were created (e.g., a-amino nitriles, a- or //-amino acid derivatives, homoallylic amines or //-amino ketones) [3b-d]. 

Allylation. Triflic acid is capable of catalyzing the reaction of allyltributylstannane with aldehydes (not ketones) in water. 

An effective chiral catalyst for asymmetric allylation of aldehydes or ketones is the complex formed between the axially chiral l,l -bi-2-naphthol (BINOL) 164 and a titanium(IV) salt." Addition of allyltributylstannane to an aldehyde using this Lewis acid gives the product homoallylic alcohol with high optical purity. For example, allylation of iso-butyraldehyde gave the alcohol 165 as a 98 2 ratio of enantiomers (1.155). Use of (5)-BINOL gave the other enantiomer of the product. 

The allylation of aldehydes can be achieved in the presence of ketones in a highly chemoselective fashion by preferential in situ conversion of aldehydes into 1-silyloxysulfonium salts, by treatment with dimethyl sulphide and TMSOTf and subsequent displacement with allyltributylstannane (eq 63). ... 

In the presence of catalytic amounts of Sc(OTf)3 and SDS, three-component Mannich-type reactions of aldehydes, amines, and silyl enol ethers proceeded smoothly in micellar systems to afford the corresponding-amino ketones or esters in high yields (Scheme 3.48). Yb(OTf)3 and Cu(OTf)2 also worked well in this system.Furthermore, three-component reactions of aldehydes, amines, and allyltributylstannane proceeded smoothly in water to afford the corresponding homoallylic amines in high yields (Scheme 3.49). ... 

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