Antimycobacterial Benzofuro[3,2-f]chromenes from a 5-Bromochromen-6-ol

In the course of our work on the synthesis of analogues of the specific antimycobacterial 3,3-dimethyl-3 H-benzofuro[3,2- F]chromene, we prepared the previously unreported 5-bromo-2,2-dimethyl-2 H-chromen-6-ol. We wish to report here an original synthetic scheme using this compound. The preparation of various 5-bromo-2,2-dimethyl-6-(aryloxy)-2 H-chromenes was first investigated. This was followed by a palladium-catalysed cyclisation reaction, which takes place only in the presence of air, and leads to 3,3-dimethyl-3 H-benzofuro[3,2- F]chromenes or 3,3-dimethyl-3 H-4,7-dioxa-10-aza-benzo[ C]fluorene. The antimycobacterial properties of these analogues have been investigated.