The lithiation of halogenated azobenzenes by a halogen-lithium exchange commonly leads to a substantial degradation of the azo-group to give hydrazine derivatives besides the desired aryl-lithium species. Yields for quenching reactions with electrophiles are therefore low. This work shows that a transmetalation reaction of easily accessible stannylated azobenzenes with methyl lithium leads to a near-quantitative lithiation of azobenzenes in para, meta and ortho position. To investigate the scope of the reaction, various lithiated azobenzenes species were quenched with a variety of electrophiles. Furthermore, mechanistic 119-Sn NMR spectroscopic studies on the formation of lithiated azobenzenes are presented. A tin-ate complex of the azobenzene could be detected at low temperatures.
|Number of pages||9|
|Journal||Chemistry - A European Journal|
|Early online date||26 Jun 2015|
|Publication status||Published - 2015|
Bibliographical noteDate of Acceptance: 06/05/2015
- azo compounds
- synthetic methods