Synthesis of phenanthridine derivatives by microwave-mediated cyclization of o-furyl(allylamino)arenes.

A novel and efficient synthesis of phenanthridines and aza analogues is reported. The key step is a microwave-mediated intramolecular Diels-Alder cyclization of o-furyl(allylamino)arenes. In the presence of a catalytic amount of acid, the DA-adduct reacts further to give the dihydrophenanthridines, which easily can be oxidized to fully aromatic compounds by air in the presence of UV light or by DDQ.

Benzene-1,3,5-triol at 105 K.

The structure of the title compound, C(6)H(6)O(3), has been redetermined at low temperature [room-temperature structure: Maartmann-Moe (1965 ▶). Acta Cryst. 19, 155-157].