Sequential mono-N-arylation of piperazine nitrogens. Part 2: The role of hydrogen bonding

Article abstract of DOI:10.1016/S0040-4039(99)01104-1

A mechanistic study of the simple sequential N-arylation of piperazine suggests that in an electron-withdrawing group (EWG) containing N-arylated piperazines, hydrogen bonding of the secondary amine hydrogen is important for its non-metal catalyzed conversion to N,N'-diaryl piperazines. A combination of synthetic experiments, molecular modeling, and NMR studies were carried out to test this hypothesis.