Fig. 2: Substrate scope of helical fluorenones.

All reactions were carried out with helical fluorenone A (0.05 mmol), diazo ester B1 (1.25 equiv.), Sc(OTf)3/NO-3 (1.3:1, 10 mol%) in 1,1,2,2-TCE (0.025 M) under air atmosphere. Isolated yields after column chromatography separation. The d.r. value was determined by 1H NMR spectroscopy and the e.e. value was determined by HPLC.