H. Kondo and E. Ochiai Ann. Chem. 1929 470 p224 reported using the iodo group to block Pschorr diazonium cyclizations into an aromatic carbon position when making polycyclic aromatics. This protocol was repeated by K. Goto and H. Sudzuki Bull. Chem. Soc. Jpn 1929 4 p163 to give...
Blocking diazonium couplings of aromatic rings