Phenanthridine and its derivatives

In addition to the survey of phenanthridine in the second edition of Rodd, a comprehensive account of the 

Tissington in Advances in Heterocyclic Chemistry, ed. A. R. Katritzky and A. J. Boulton, Academic Press, New York, 1971, vol. 13, p. 315), Reviews of alkaloids based on phenanthridine regularly update knowledge in this area (S.D. Phillips and R.N. Castle, J. heterocyclic Chem., 1981, 18, 223). 

Further examples of the cyclisation of biphei ls to phenanthridines include carbanion based methods. In the case of the 2-amlnobiphenyl (38). metallation is directed to the 2 -position by the 3 -methoxy group, and cyclisation to the phenanthridine follows formylation (N. S. Narasimhan, F. S. Chandrachood and N.R. Shete. Tetrahedron, 1981, 37, 825). 

The amide (39) affords a low yield of the 6-ary1-5-methyl phenanthridinium salt on treatment with t-butyl lithium (D. Hellwinkel, R. Lenz and F. Lammerzahl. Tetrahedron, 1983, 2073). Formanilides yield phenanthridines on treatment with phosphorus pentachloride (N.S. Narasimhan, toa, ait. ) 

A different approach to the cyclisation of biphei l derivatives involves the generation of imidoyl radicals from Schiff bases (40) using diisopropyl peroa -dicarbonate. The intramolecular homolytic substitution is apparently not regiospecific since the methozy derivative (40 R=0Me) affords a mixture of isomers (R. Leardini. A. Tundo and 6. Zanardi, Synthesis, 1985. 107). 

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