Homoallylic amines Allyltributyltin

Lewis acid-mediated nucleophilic additions to carbon-nitrogen double bond have been applied to the synthesis of homoallylic amines.1 3 Three-component syntheses of homoallylic amines starting from aldehydes, amines, and allyltributyltin are realized in the presence of Lewis acids such as La(OTf)3, Bi(OTf)3, LiClOa (Equation (47)).154-156... 

Crotyltins react regioselectively with a-alkylimines to give exclusively branched products with an excellent syn/anti selectivity up to 30 1, when the imine activation is conducted at —78 °C prior to the addition of the crotyltin. This selectivity which is consistent with an acyclic transition state is rapidly fading when operating at a higher temperature. This would be the result of an equilibrium between the two imine/Lewis acid complexes (equation 14). There are very few examples with a, /3-unsaturated aldimines, but it has to be noted that under TiCU activation, they are able to undergo a double nucleophilic addition of ketene silyl acetal and allyltributyltin to give the homoallylic amine in a reasonable yield . 

Three-component reactions of aldehydes, amines, and allyltributyltin also proceeded smoothly in micellar systems with Sc(OTf)3 as Lewis acid catalyst, to afford the corresponding homoallylic amines in high yields (Eq. 19) [68]. Not only aromatic aldehydes but also aliphatic, unsaturated, and heterocyclic aldehydes worked well. The procedure is very simple—merely mixing an aldehyde, an amine, and allyltributyltin in the presence of Sc(OTf)3 and SDS in water no homoallylic alcohol (an adduct between an aldehyde and allyltributyltin) was produced. It was suggested that imine formation from aldehydes and amines was very fast under these conditions, and that the selective activation of imines rather than aldehydes was achieved. 

The reaction of imines with allyltributyltin provides a useful route for the synthesis of homoallylic amines [30]. The reaction is generally carried out in the presence of a Lewis acid in organic solvents under strictly anhydrous conditions [31], because most imines, Lewis acids, and the organotin reagents used are hygroscopic and decompose easily in the presence of even a small amount of water [32]. It was found that three-component reactions of aldehydes, amines, and allyltributyltin proceed smoothly in micellar systems using Sc(OTf)3 as a Lewis acid catalyst (Eq. 7) [33]. The reaction of benzaldehyde, aniline, and allyltributyltin was chosen as a model, and several reaction conditions were examined. While the reaction proceeded sluggishly in the presence of Sc(OTf)3 without SDS or in the presence... 

There are very few examples with a,/3-unsaturated aldimines, but it has to be noted that under TiCb activation, they are able to undergo a 1,4-nucleophilic addition of ketene silyl acetal followed by a 1,2-addition of the allyltributyltin on the resulting imine giving the homoallylic amine in good yield [260]. 

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