An efficient Pd-catalyzed cross-dehydrogenative coupling of heteroarenes with styrenes and other olefinic substrates has been developed. This alkenylation paradigm encompasses a wide range of substrates and provides a straightforward approach toward C2-E-alkenylated azole motifs.
Inert
aryl methyl ethers as coupling components via C–O
activation have been established with a Ni catalyst for C–H
activation of heteroarene. The key to simultaneous C–H/C–O
bond activation is the use of sterically demanding o-tolylMgBr. The protocol is effective for a wide scope of substrates
including naphthyl methyl ethers, anisoles, and a variety of other
heteroarene derivatives. Detailed mechanistic studies indicated that
the C–O cleavage is assisted via synergistic effect of nickel
and Grignard reagent in this C–H/C–O reaction, which
is supported by DFT calculation. At this stage, single-electron transfer
can be ruled out as a main operative process for this tandem strategy.
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