Catalytically High Efficiency Allylating Reaction

Allylboronic acid derivatives have been widely used as allylating reagents for organic synthesis. Recently, Kobayashi et al. have developed that 2-allyl-5,5-dimethyl-1,3,2-dioxaborinane (1) is a superior efficient allylating reagent for catalytic allylation via the boron-to-zinc transmetallation. In this reaction, Zn(HMDS)₂ salt formed from 1,1,1,3,3,3-hexamethyldisilazane (=HMDS) and zinc metal is an effective catalyst, and its catalyzed allylations of carbonyl compounds and their imine or hydrazone derivatives successfully proceed when 0.1 mol% amount of the catalyst is used. The NMR experiments show that this reaction proceeds via the allylzincamide as a reaction intermediate. Furthermore, enantiometic allylations are accomplished by using chiral diamine ligands. Thus, the new allylation using 1 is an efficient allylating method because of its availability for various substances and the halogen-free procedure.