Intramolecular Direct C−H Arylation Approach to Fused Purines. Synthesis of Purino[8,9-<i>f</i>]phenanthridines and 5,6-Dihydropurino[8,9-<i>a</i>]isoquinolines§Dedicated to the memory of Keith Fagnou.

Intramolecular C−H arylations were employed as a key step in the synthesis of hitherto unknown fused purine systems: 13-substituted purino[8,9-f]phenanthridines and 11-substituted 5,6-dihydropurino[8,9-a]isoquinolines. The purino[8,9-f]phenanthridines were prepared in moderate yields by double C−H arylations of 9-phenylpurines with 1,2-diiodobenzene or, more efficiently, by consecutive Suzuki coupling of 9-(2-bromophenyl)purines with 2-bromophenylboronic acid followed by intramolecular C−H arylation. 5,6-Dihydropurino[8,9-a]isoquinolines were prepared in quantitative yields by intramolecular C−H arylations of 9-(2-chlorophenethyl)purines.