Cu(I)-catalyzed enantioselective [2 + 2] cycloaddition of 1-methoxyallenylsilane with alpha-imino ester: chiral synthesis of alpha,beta-unsaturated acylsilanes.
[reaction: see text] The catalytic, enantioselective [2 + 2] cycloaddition reaction of 1-methoxyallenylsilanes with alpha-imino ester has been achieved by means of the [Cu(MeCN)(4)]BF(4)/(R)-Tol-BINAP catalyst to afford 3-methylene-azetidine 2-carboxylates in good yields and with excellent enantiomeric excesses. The acid-catalyzed ring opening of the azetidines afforded chiral acylsilanes quantitatively.