Ligand-Controlled Selective Synthesis of Indoles and Benzofurans from Secondary Anilines
Chunchen Yuan1, Changbo Jia1, Wenlong Zhang1
1School of Chemistry and Chemical Engineering, Xiushan Campus Anhui University of Technology, Ma'anshan, Anhui 243032, China.
Abstract:
A ligand-controlled method for the selective synthesis of indoles and benzofurans from secondary anilines has been discovered. A six-ring palladacycle intermediate may be involved in this process by olefins as a transient directing mediator to give indoles. The indole/benzofuran ratio can be easily tuned by the MPAA ligand. Various substituted secondary anilines were well-tolerated, affording the corresponding products in moderate to good yields. Indole-derived drugs such as JWH-081, BB-22, and ML-098 could be obtained using our new method to achieve their precursors. Preliminary mechanistic studies indicated that BQ is the key factor in avoiding the β-H elimination of insertion species.
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