Spiro Bis(isoxazole) as a New Chiral Ligand

A novel bis(isoxazole) ligand, (M*)-4,4 ',5,5',6,6',7,7'-octahydro-7,7'-spirobi[benzo[c]isoxazole] (5) bearing a spiro chirality was designed and synthesized.Characterization of the ligand and its application to the enantioselective tandem cyclizaton of alkenyl alcohol via oxy-palladation are described.Recently, transition metal-catalyzed asymmetric reactions have acquired prominence in synthetic organic chemistry.The design of optically active ligands which have both strong affinity for metal and a chiral backbone to construct an effective asymmetric environment is the key to the development of new enantioselective reactions. 1Since a chiral spiro skeleton is quite rigid and able to possess unique chirality, several applications of asymmetric spiro ligands have been reported. 2We have so far reported the novel spiro bis(isoxazoline) ligands (SPRIXs) (Figure 1) bearing a chiral spiro skeleton and two isoxazoline rings, and demonstrated the first example for the use of an isoxazoline ligand in transition metal-catalyzed enantioselective reaction.3a Utilizing the good affinity of SPRIXs to Pd(II) salts and the