Four benzodipyrans namely, 2,2,8,8-tetramethyl-2H,8H-benzo[1,2-b:5,4-b'][1,2-b:3,4-b']dipyrans (7/8), 2,8-diphenyl-4H,6H-benzo[1,2b:5,4-b']dipyran-4,6-dione(9) and 2,8-diphenyl-4H,10H-benzo[1,2-b:3,4-b']dipyran-4,10-dione (10) have been synthesized. The key step in the synthesis involves cross condensation reactions between the enolates of 4,6-(1) and 2,4-diacetyl-(2)-resorcinols with acetone and benzoyl chloride.
A. Banerji, Goomer, N. C., and Kalena, G. P., “Enolates of Diacetyl Resorcinols: Application to Synthesis of Benzodipyrans”, Indian Journal of Chemistry Section B-Organic Chemistry Including Medicinal Chemistry, vol. 27, pp. 981–984, 1988.