Rhodium-catalyzed asymmetric formal cycloadditions of racemic butadiene monoxide with imines.

A simple chiral sulfur-alkene hybrid ligand has proven to be highly effective for rhodium-catalyzed formal cycloaddition reactions of racemic butadiene monoxide and imines to furnish spirooxindole oxazolidines or 1,3-oxazolidines with high yields and stereoselectivities. A possible dynamic kinetic resolution as well as a kinetic resolution is considered to be involved in this catalytic process.