Efficiently Constructing Tetrahydroquinolines through Cascade Radical Additions and Cyclizations under the Catalysis of Cu~I

摘要

An efficient method has been developed for the construction of tetrahydroquinolines from N,N-dimethylanilines and electron-deficient alkenes based on CuCl/O2. A wide scope of substrates could be well tolerated, and excellent yields of the products were obtained. A series of control experiments and kinetic isotope effect experiments have been performed to gain insight of the catalytic reaction pathway. The reaction is probably initiated by the reaction of Cu~I and molecular oxygen to give copper(II) superoxide (Cu~(II)OO*) as the key reactive intermediate. The formed Cu~(II)OO* species can directly abstract a hydrogen from the α-site of nitrogen to give the α-amino radical intermediate, which then finishes the transformation via radical addition and cyclization.