Nickel‐Catalyzed Cyclization of ortho‐Iodoketoximes and ortho‐Iodoketimines with Alkynes: Synthesis of Highly Substituted Isoquinolines and Isoquinolinium Salts |
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Authors: | Wei‐Chun Shih Chu‐Chun Teng Dr Kanniyappan Parthasarathy Prof?Dr Chien‐Hong Cheng |
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Institution: | Department of Chemistry, National Tsing Hua University, Hsinchu 30013 (Taiwan), Fax: (+886)?3‐572‐4698 http://mx.nthu.edu.tw/%7Echcheng |
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Abstract: | A convenient method for the synthesis of highly substituted isoquinolines and isoquinolinium salts by the nickel‐catalyzed cyclization of ortho‐haloketoximes and ‐ketimines, respectively, with alkynes is described. The reaction of ortho‐haloketoximes and various alkynes in the presence of Ni(PPh3)2Br2] and zinc powder in a mixture of acetonitrile and tetrahydrofuran at 80 °C for 15 hours gave 1,3,4‐trisubstituted isoquinoline products in moderate to excellent yields and high regioselectivity. The corresponding isoquinoline N‐oxide was found to be the intermediate in the cyclization reaction pathway. In contrast, the reaction of ortho‐haloketimines and alkynes under similar catalytic conditions in tetrahydrofuran at 70 °C for two hours gave 1,2,3,4‐tetrasubstituted isoquinolinium salts in good to excellent yields. |
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Keywords: | alkynes cyclization isoquinolines ketimines nickel |
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