Catalytic Asymmetric Cascade Using Spiro-Pyrrolidine Organocatalyst: Efficient Construction of Hydrophenanthridine Derivatives

A newly developed SPD (spiro-pyrrolidine) organocatalyst has been demonstrated to enable an asymmetric aza-Michael/Michael/aldol cyclization cascade, in which two six-membered rings (B/C) and three stereocenters have been constructed in a catalytic one-step process. It is so far the most efficient method for construction of hydro-phenanthridine derivatives featuring high enantioselectivity. The trans- or cis-fusedB/C-ringscan be selectively assembled in a substrate -controlled manner. Moreover, this cascade could magnify to gram scale without loss of enanioselectivity.