Nitrated Confined Imidodiphosphates Enable a Catalytic Asymmetric Oxa-Pictet–Spengler Reaction

The development of
a highly enantioselective catalytic oxa-Pictet–Spengler
reaction has proven a great challenge for chemical synthesis. We now
report the first example of such a process, which was realized by
utilizing a nitrated confined imidodiphosphoric acid catalyst. Our
approach provides substituted isochroman derivatives from both aliphatic
and aromatic aldehydes with high yields and excellent enantioselectivities.
DFT calculations provide insight into the reaction mechanism.