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Enantioselective Synthesis of Chiral Tetrahydroisoquinolines by Iridium‐Catalyzed Asymmetric Hydrogenation of Enamines
Author(s) -
Yan PuCha,
Xie JianHua,
Hou GuoHua,
Wang LiXin,
Zhou QiLin
Publication year - 2009
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.200900602
Subject(s) - chemistry , iridium , enantioselective synthesis , phosphoramidite , asymmetric hydrogenation , catalysis , deuterium , iodide , medicinal chemistry , kinetic isotope effect , organic chemistry , dna , biochemistry , physics , quantum mechanics , oligonucleotide
Chiral iridium complexes based on spiro phosphoramidite ligands are demonstrated to be highly efficient catalysts for the asymmetric hydrogenation of unfunctionalized enamines with an exocyclic double bond. In combination with excess iodine or potassium iodide and under hydrogen pressure, the complex Ir/( S a , R , R )‐ 3a provides chiral N ‐alkyltetrahydroisoquinolines in high yields with up to 98% ee . The L/Ir ratio of 2:1 is crucial for obtaining a high reaction rate and enantioselectivity. A deuterium labeling experiment showed that an inverse isotope effect exists in this reaction. A possible catalytic cycle including an iridium(III) species bearing two monophosphoramidite ligands is also proposed.