[3+2] Annulation of MBH Adducts Promoted by Bifunctional Phosphines

Significance

Lu and co-workers report a highly enantioselective [3+2] annulation of MBH adducts 2 and isatin-derived activated alkenes 1. The reactions were promoted by bifunctional phosphine 3, which is easily accessible from threonine. Instead of commonly employed allenes and alkynes for [3+2] cycloadditions, the authors applied MBH adducts 2 as a C₃ synthon. The obtained spiro­oxindoles 4 posses two contiguous quaternary centers with various functional groups. Also, a one-pot procedure with N-PMB-isatin and malononitrile under the reaction condition affords the desired product 4 with the same reactivity and enantioselectivity.