Allylation imines

A catalytic amount of TBAF is effective in the allylation of aromatic imines with 10 in refluxing THF." Similar to the TBAF-catalyzed carbonyl allylation, the imine allylation is promoted by a fluoride-triggered autocatalytic cycle. 

The 7t-allylpalladium-TBAF co-catalyst system described in Equation (20) enables the allylation of aromatic imines as well as aldehydes at room temperature.93 Chiral 7t-allylpalladium complex 21 is an efficient asymmetric catalyst of the imine allylation (Equation (29)).93 126... 

Examples of imine allylation in aqueous media are rather limited compared with the carbonyl version. This is ascribed to the lower electrophilicity of the C=N function of imines and its ease of hydrolysis to carbonyl compounds. In order to overcome the undesired side-reactions, sulfonimines in place of simple imines are success-fully used for the allylation under aqueous conditions (Equation (61)). Grotylation of cr-sulfonimino esters gives... 

An alternative to the Bach procedure (BocN3/FeCl2) for the synthesis of Boc-protected sulfimides was developed in 2002 (Scheme 76) [171]. Oxaziri-dine 312, prepared from diethyl ketomalonate, was found to iminate allylic sulfides 309 at low temperatures. The resulting allyl sulfimide (not shown) immediately rearranged to protected amines 313 in high yields. The possibility of preparing a-amino acid derivatives like 314 is a noteworthy feature although the compounds are, of course, racemic. 

Alfylations. A direct preparation of allyltin reagents from allyl halides is accomplished by treatment with SnCl. Allytributylstannane is activated by SnClj in MeCN for reaction with carbonyl compounds and imines. Allylic alcohols and cyclic carbonates can also be used as allylating agents for amines and aldehydes, respectively. 

In analogy with the enantioselective carbonyl-ene reactions (Chapter 2, Section 2.11), an attractive but much less well precedented alternative to imine allylations is enantioselective imino-ene reactions. The first such example was reported by Lectka, who found that the Tol-BINAP copper complex 216 promoted the addition of unactivated alkenes to N-tosyl imine 110 (Equation 27) [31, 153, 173]. This transformation provided the homoallylic a-amino acid 270 in 90 % yield and 99 % ee. 

---