Chiral N,N′-dioxide/Co(ii)-promoted asymmetric 1,3-dipolar cycloaddition of nitrones with methyleneindolinones.

A chiral N,N′-dioxide/Co(BF4)2·6H2O complex catalytic system has been developed to efficiently catalyze the asymmetric 1,3-dipolar cycloaddition of nitrones with methyleneindolinones. The corresponding chiral multisubstituted spiroisoxazolidines with three contiguous quaternary–tertiary stereocenters were obtained in moderate to high yields with excellent dr and ee values (up to 97% yield, ＞19 : 1 dr and 98% ee). [ABSTRACT FROM AUTHOR]