Construction of Spiro Skeletons in 2,2',3,3'-Tetrahydro-1,1'- spirobi[1H-indene]-7,7'-diol (SPINOL) and Analogues

Abstract

1,1'-Spirobiindane possesses a new type of skeleton for chiral ligands developed in the early 21st century, which has the characteristics of C2-symmetry, strong rigidity, high stability, and ease of modification. Zhou et al. developed 2,2',3,3'-tetrahydro-1,1'-spirobi[1H-indene]-7,7'-diol (SPINOL) into series of chiral ligands and catalysts, and achieved great success in the field of catalytic asymmetric synthesis. These ligands and catalysts bearing 1,1'-spirobiindane skeleton are considered as few "privileged chiral ligands and catalysts". Though catalytic asymmetric syntheses have appeared, in the present methods SPINOL and analogues are usually obtained in racemic forms, which require further chiral resolution. Laborious synthetic and resolution steps limit their productions in industrial scale. Therefore, it is urgent as well as challenging to develop efficient method of asymmetric catalytic synthesis of chiral spiro ligands from cheap and readily available raw materials. The synthetic methods of SPINOL and analgoues in the past 20 years are summarized, including those bearing heteroatoms in the spiro skeleton, in the hope of sparking new ideas for the construction of spiro skeletons in ligands or catalysts.