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DOI: 10.1055/s-0034-1379553
Synthesis of Phenanthridines from Diaryliodonium Salts and Nitriles
Publication History
Publication Date:
18 November 2014 (online)
Significance
Reported is the synthesis of phenanthridines 3 via the copper-catalyzed coupling reaction of diaryliodonium salts 1 with aryl nitriles 2, followed by a cyclization. Diaryliodonium salts were obtained from corresponding o-iodo-biphenyl derivatives. EDG-containing 1 and 2 gave higher yields in comparison to EWG-containing 1 and 2. A mechanism was also proposed, involving oxidative insertion of Cu(OTf)2 into the Ar–I bond of 1, C–N bond formation with 2 to form an N-aryl nitrilium cation, and alternate ring electrophilic substitution.
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Comment
Phenanthridines are important heterocycles due to their presence in biologically active compounds and natural products, and because of their pharmacological properties (see Review below). Phenanthridines are generally synthesized by heterocyclic ring bridging of the biaryl moiety (see Book below and M. A. Siddiqui, V. Snieckus Tetrahedron Lett. 1988, 29, 5463). Although the new method provides a general strategy for the preparation of phenanthridines, the reaction is carried out at comparatively high temperatures, and yields are low to moderate for many of the substrates tested.
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Review
T. C. Johnstone, G. Y. Park, S. J. Lippard Anticancer Res. 2014, 34, 471–476.
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Book
P. A. Keller Phenanthridines, In Science of Synthesis, Vol. 15; D. StC. Black, Ed.; Georg Thieme Verlag: Stuttgart, New York, 2005, 1065–1088.
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