An improved synthesis of dibenzofurans by a free-radical cyclization

Article abstract of DOI:10.1021/jo00121a016

Reaction conditions for the formation of dibenzofurans from diazotized o-(aryloxy)anilines have been examined. Several promoters (hydroquinone, SnCl₂, NaI, CuSO₄, FeSO₄, etc.) have been discovered; these act as electron donors and promote a free-radical mechanism. The best of these is FeSO₄ which shortens the reaction time from hours to minutes and contributes to high yields (77-83%). We have been able to transform the cyclization to a reliable and convenient synthesis.