Palladium-Catalyzed Enantioselective Intramolecular Heck Dearomative Annulation of Indoles with N-Tosylhydrazones
Yue Ma1, Qing-Hui Liu1, Ya-Ping Han1
1School of Chemical Engineering and Technology, Hebei University of Technology, Tianjin 300130, People's Republic of China.
Abstract:
An elegant Pd(dba)2-catalyzed enantioselective Heck dearomative annulation of indoles and N-tosylhydrazones for the straightforward assembly of structurally diverse optically active indoline scaffolds containing the quaternary carbon centers at the C2 position has been developed. The tandem protocol, which utilized a Pd(dba)2/BINOL-based phosphoramidite ligand as the catalytic system, proceeded smoothly through successive oxidative addition, intramolecular carbon palladation, migratory insertion, and β-elimination sequences, leading to the chiral indoline derivatives in moderate to excellent yields, with excellent enantioselectivities and diastereoselectivities. In addition, the synthetic practicability of the catalytic system was underlined by a scaled-up experiment and the late-stage derivatization of the products, thus highlighting the potential applications in synthetic chemistry, medicinal chemistry, and material science.
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