Synthesis of 1,1'-Spirobiindane-7,7'-Disulfonic Acid and Disulfonimide: Application for Catalytic Asymmetric Aminalization.

1,1'-Spirobiindane-7,7'-disulfonic acid (SPISA) and 1,1'-spirobiindane-7,7'-disulfonimide were synthesized from 1,1'-spirobiindane-7,7'-diol (SPINOL) in 4 steps using a Pd-catalyzed Newman-Kwart rearrangement as a key step. These new catalysts possessing a rigid spirocyclic backbone were evaluated in a catalytic asymmetric aminalization reaction, and SPISA/iPr2 NEt exhibited high enantioselectivity, demonstrating the utility of SPISA as a chiral Brønsted acid catalyst.