Enantioselective intermolecular [2+2] photocycloadditions of isoquinolone mediated by a chiral hydrogen-bonding template

The first examples of enantioselective intermolecular [2+2] photocycloadditions of isoquinolone with alkenes are reported. Photoreactions were carried out at low temperature in the presence of a chiral hydrogen-bonding template, which effectively shields one face of the substrate through formation of a hydrogen-bonded supramolecular complex. Functionalized cyclobutane products were obtained in excellent yields (86−98%) and with outstanding regio-, diastereo-, and enantioselectivity (88−99% ee)