Enantioselective synthesis of spiro-N,O-ketals via iridium and Brønsted acid co-catalyzed asymmetric formal [4+2] cycloaddition

An asymmetric formal [4+2] cycloaddition of cyclic enamides with 2-(1-hydroxyallyl)phenol via iridium and Brønsted acid co-catalysis has been achieved to afford chiral N -unsubstituted spiro- N , O -ketals.