Fig. 2: Optimization studies.
From: Chiral Brønsted acid-controlled intermolecular asymmetric [2 + 2] photocycloadditions
aYields and diastereomer ratios determined by 1H NMR spectroscopy. bEnantiomeric excess of the major diastereomer determined by chiral HPLC. cRatio of trans–cis isomer to trans–trans isomer. dConducted at room temperature. eConducted in the dark.
