Enantioselective Rhodium-Catalyzed Addition of Imines and Oximes to Allenes

The ever-increasing interest in catalytic reactions has made significant progress in the improvement of the synthetic efficiency. To achieve the goal of atom economy and efficiency, transition metal catalysis has demonstrated to be of great potential. In this context, I developed a chemo-, regio-, and enantioselective hydroamination of allenes with benzophenone imines and oximes. These methods permit the atom economic synthesis of valuable branched allylic amine and nitrone derivatives. Rhodium-catalyzed hydroamination of allenes with benzophenone imine as ammonia carrier furnished α-chiral primary allylic amines followed by simple hydrolysis and amine protection strategy. The reaction was achieved in good to excellent yields, exclusive branched selectivities, and excellent enantioselectivities via a rhodium(I)/Josiphos catalyst. Expanding this methodology to elucidate, the first rhodium-catalyzed chemo- and enantioselective hydroamination of allenes with benzophenone oxime is reported. The asymmetric synthesis of branched allylic nitrones instead of oxime ethers was obtained in good to almost quantitative yields and excellent enantioselectivities. Furthermore, the chiral allylic nitrone was subjected to 1,3-dipolar cycloaddition highlighting the synthetic potential of these building blocks.