Electrophilic Amination of 4-Fluorophenol with Diazenes:  A Complete Removal of the Fluorine Atom

Abstract

The electrophilic amination of 2-fluorophenol, 4-fluorophenol, and 2-chlorophenol was observed to occur as a result of their treatment with diazenes 1-4 under mild reaction conditions in the presence of ZrCl(4). The products originating from the 2-fluorophenol or 2-chlorophenol can be considered as "normal" products of amination. On the other hand, the 2-chloro-4-amino-substituted phenols obtained from the 4-fluorophenol seem to be formed in a process that involves an ipso amination, the complete removal of the fluorine atom, and the introduction of the chlorine atom.

Synthesis of N‐Aryl‐ and N‐Alkenylhydrazides through C(sp2)−N Bond Construction

“…In this conversion, halogen migrated from para‐ to ortho‐ with respect to the ‐OH. If 4‐fluorophenol 54 c was used as the starting material, a 2‐chloro‐4‐hydrazino substituted phenol 55 c was obtained instead of the F migration product [22b] . The process may involve an ipso addition of arenes to azodicarboxylates to form I , with further elimination of ZrCl 4 F − to give II .…”

New synthetic applications and biological activity of diazenes

“…On the other hand, the migration of fluorine on organic substrates has been observed rarely and has involved the use of high energy intermediates or excited molecules [33] Only very recently a unique 1,3-shift of fluorine on fullerene C 60 F 36 at room temperature has been reported by Avent and Taylor [34]. To get more insight into unusual amination we compared reactions of 2-fluorophenol and 4-fluorophenol with various diazenes [35]. When electrophilic aromatic substitution is performed on these substrates, the new The electrophilic amination of 4-fluorophenol with the same diazenes in the presence of ZrCl 4 led to 4-aminated 2-chlorophenols 39-43 (yield: 41-87%).…”