Phosphine‐Catalyzed (3+2) Annulation of Morita‐Baylis‐Hillman Carbonates with Pyrazolinone‐Derived Ketimines: Synthesis of Spirodihydropyrrole‐Dihydropyrazolones

Abstract A phosphine‐catalyzed (3+2) annulation of Morita‐Baylis‐Hillman carbonates with pyrazolinone‐derived ketimines has been achieved to give various spirodihydropyrrole‐dihydropyrazolones in moderate to high yields with good diastereoselectivities. The reaction tolerated diverse MBH carbonates and ketimines. Both scale‐up reaction and further transformation of the product were successfully performed. In addition, up to 98 % ee of chiral product was obtained with the use of chiral bifunctional phosphine.