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Asymmetric Hydrogenation of Exocyclic α,β-Unsaturated Nitriles: An Access to Chiral 2-Benzocyclic Acetonitriles and
Xiaoxue Wu1, Rui Zang1, Ling Ma1
1Key Laboratory of Radiopharmaceuticals, College of Chemistry, Beijing Normal University, Beijing 100875, China.
Abstract:
A highly efficient and enantioselective hydrogenation of exocyclic α,β-unsaturated nitriles catalyzed by the Rh-JosiPhos complex for synthesis of the chiral 2-benzocyclic acetonitriles has been developed. Both (Z)- and (E)-isomers of exocyclic α,β-unsaturated nitriles with various benzocyclic structures, including heterocyclic (chroman and tetrahydroquinoline) scaffolds, were hydrogenated successfully, achieving excellent enantioselectivities (up to 97% ee) and high turnover numbers (TON up to 4000). Furthermore, this methodology provides an efficient, concise, and practical synthetic route to the sleep agent (S)-Ramelteon.
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