RESUMO
An 8-aminoquinoline-directed, copper/1,10-phenanthroline-mediated selective mono-organothiolation of the C-H bond in ferroceneamide has been developed using aryl/alkyl disulfide substrates. The sequential ferrocene C-H organochalcogenation (chalcogen = S, Se, and Te) has also been established for the synthesis of novel hybrid unsymmetrical aryl chalcogenides with the aid of a catalytic amount of Cu(OAc)2 under ambient reaction conditions. The developed protocol results in a broad functional group tolerance to allow alkyl-, aryl-, heteroaryl-, bromo-, chloro-, and nitro-containing diorgano dichalcogenides as coupling partners. Furthermore, the 8-aminoquinoline directing group is easily removed to afford the aldehyde functionality after C-H organochalcogenation. A mechanistic understanding of the copper-mediated selective mono-organothiolation reaction suggests that the rigid bicoordinated 1,10-phenanthroline ligand and freshly generated copper(II) from Cu(I) in the less polar solvent acetonitrile are crucial to the selective mono-C-H functionalization of ferroceneamide.
RESUMO
A synthetic method has been developed for the synthesis of unsymmetrical ferrocene aryl chalcogenides by C-H activation of ferroceneamide using 8-aminoquinoline as a directing group, aryl dichalcogenides, and copper(II) catalyst in the presence of silver acetate oxidant at 80 °C in DMSO. The developed methodology is quite general and mild to access three unsymmetrical diaryl chalcogenides (sulfide, selenide, and telluride) and also amenable to aryl dichalcogenides with sensitive bromo, chloro, and nitro functionalities. Further, ferrocene aryl tellurides have been obtained in moderate yields for the first time by the developed C-H activation approach. In the mechanistic part, it seems that the presence of a rigid chelating directing ligand is crucial for the aryl chalcogenation reaction of C-H bond under copper catalysis as the nonrigid bidentate directing ligands were unsuccessful for the transformation.
