Remote Asymmetric Induction Using Acetate-Type Vinylketene Silyl N,O-Acetals.

Remote asymmetric induction by the vinylogous Mukaiyama aldol reaction using the acetate-type vinylketene silyl N,O-acetal possessing a chiral auxiliary has been achieved. The silyl N,O-acetal derived from crotonate and l-valine afforded the O-silylated 5R- and 5S-adducts selectively by treatment with SnCl4 and BF3·OEt2, respectively. The SnCl4-mediated isomerization of silyl dienol ether was found, and the resulting major isomer showed high reactivity to give γ-adduct in high stereoselectivity.