The catalytic asymmetric [2+2] cycloaddition proceeds between 3-(2-alkenoyl)-1, 3-oxazolidin-2-ones and 1, 2-propadienyl sulfides having various substituents at 1-position, affording methylenecyclobutane derivatives with high optical purity. Seven and eight membered carbocycles with chiral side chains are prepared by the ring cleavage reaction and successive cationic cyclization of the chiral methylenecyclobutane derivatives having ω-alkenyl substituents.
- catalytic asymmetric [2+2] cycloaddition reaction
- cationic cyclization
- chiral titanium reagent