High pressure-assisted low-loading asymmetric organocatalytic conjugate addition of nitroalkanes to chalcones

The application of high pressure (up to 9 kbar) allows for relatively fast (1–5 h) and highly enantioselective 1,4-addition of nitromethane and 2-nitropropane to chalcones at room temperature with substantial reduction of catalyst loading (0.2–1 mol% of cinchona alkaloid-based thioureas and squaramides). Various γ-nitroketones were obtained at 9 kbar with high yield and enantioselectivity (up to 98%), whereas in control experiments at atmospheric pressure usually only a small amount (<10%) of products were formed after 20 h.