Sakurai allylation reaction asymmetric catalytic reactions

Asymmetric allylation is a valuable method for constructing chiral functionalized structures, and therefore many chiral allylmetal reagents directed toward a high level of asymmetric induction have been designed and synthesized. Although some of them have exhibited good to excellent enantio- and diastereoselectivities in reactions with achiral aldehydes, Yamamoto et al. developed the first method for a catalytic process in 1991 [43a]. CAB 3a has a powerful activity in the Sakurai-Hosomi allyla-... 

The development of asymmetric catalytic Sakurai reactions offers major challenges. As mentioned earlier, the Bp3-catalyzed allylation stops at the boron alkoxide 86 and FSiMe (87). The silyl ether 88 is not formed, nor is BF3 regenerated. Likewise, the use of TiCU yields the titanium alkoxide 89 and ClSiMe3 (90). The silyl ether 88 is not produced and TiCLt is not released. For the reaction to be catalytic, however, the alkoxide must react with the halotrimethylsilane (as in 91 with 92) to regenerate the catalyst MXn. Furthermore, the acyclic nature of the transition state makes any form of asymmetric control difficult to achieve. 

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