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Synthesis 1992; 1992(12): 1245-1248
DOI: 10.1055/s-1992-26350
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Use of the N-Formyliminium Ion Cyclization for the Synthesis of 3-Aryl-1,2,3,4-tetrahydroisoquinolines

Bruce E. Maryanoff* , Mary C. Rebarchak
  • *Chemical Research Department, Janssen Research Foundation and Medicinal Chemistry Department, R. W. Johnson Pharmaceutical Research Institute, Spring House, Pennsylvania 19477, USA
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Publication Date:
29 April 2002 (online)

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Classical cyclization procedures for the synthesis of 3-arylisoquinolines are fraught with complications. Here, we present the application of an N-acyliminium cyclization to such target molecules. N-(1,2-diarylethyl)formamides 1, 4a-4d, and 4f were cyclized to the respective tetrahydroisoquinolines by using paraformaldehyde under mildly acidic conditions. Yields ranged from good to excellent. Cyclization of 4e was unsuccessful possibly because the presence of the 4-methoxyphenyl group leads to ionization of the formamido group.