Original Synthesis of Substituted 6H-Benzo[c]chromene Derivatives Using a TDAE and Pd-Catalyzed Cyclization Strategy.

We report an efficient synthetic method for the preparation of 6H-benzo[c]chromenes from substituted 1-(2'-bromo-[1,1'-biphenyl]-2-yl)-2-phenylethanols. These intermediates were obtained via a TDAE-initiated reaction between new substituted 2'-bromo-[1,1'-biphenyl]-2-carbaldehyde derivatives and substituted nitrobenzylic chlorides. The second step involved a palladium-catalyzed intramolecular O-arylation of the alcohol intermediate under microwave irradiation (110 °C for 1.5 h). The structure of 6H-benzo[c]chromene derivatives was confirmed by X-ray crystallography of product 5c.