Copper-Mediated Selective Mono- and Sequential Organochalcogenation of C–H Bonds: Synthesis of Hybrid Unsymmetrical Aryl Ferrocene Chalcogenides

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.