Construction Of Chiral Quaternary Carbon Centers Containing Pyrrole Heterocycle Mediated By Magnesium

The 3,3'-disubstituted oxindole framework,which contains a tetrasubstituted carbon stereocenter at the C3-position,is the structural motif frequently found in many biologically active molecules and natural products.Using 3-monosubstituted oxindoles as nucleophiles reacting with different electrophiles should belong to the most straightforward methodology for constructing a chiral quarter carbon stereocenter at the C3-position of the oxindole framework.A magnesium catalyzed asymmetric conjugate reaction of C3-pyrrolyl-oxindoles with terminal alkynones is presented.The current asymmetric conjugate reaction relies on the development of novel combinational magnesium catalysis involving two chiral ligands.The current protocol proceeds smoothly and gives the corresponding enantioenriched 3,3-disubstituted oxindole skeletons with good enantioselectivities.Furthermore,the conjugate adducts could be transferred to spiro oxindole structures containing an eight-membered ring in high ee values.The mild reaction conditions and wide applicability of the substrate provide an efficient route for the synthesis of ring compounds in spirocyclic oxindole.