Synthesis of Novel Chiral Spiro Bis(pyrazole) Ligands

The first synthesis of spiro bis(pyrazole) ligands, 2,2 ',4,4'-tetrahydro-6,6'-spirobi[5H-cycopentapyrazole] (1a) and 2,2'-dibenzyl-2,2',4,4'-tetrahydro-6,6'-spirobi[5H-cycopentapyrazole] (1b) was achieved.The application of spiro bis(pyrazole) ligand to asymmetric catalysis was also examined.The design of enantiomerically pure chiral ligands is one of the most important challenges in the development of asymmetric catalysis. 1We have previously reported the first design and synthesis of the