Synthesis 1990; 1990(6): 535-538
DOI: 10.1055/s-1990-26933
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A New Approach to the Synthesis of 2-Methyl-4H-furo[3,2-c][1]benzopyran-4-ones and 2H,5H-Pyrano[3,2-c][1]benzopyran-5-ones

R. Jagdish Kumar* , G. L. David Krupadanam, G. Srimannarayana
  • *Department of Chemistry, Osmania University, Hyderabad-7, India
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Publication Date:
17 September 2002 (online)

The reaction of various 4-hydroxy-2H-[1]benzopyran-2-ones 1 with allyl bromide and potassium carbonate in acetone yielded the corresponding 4-allyloxy derivatives 2. Claisen rearrangement of 2 gave 3-allyl-4-hydroxy-2H-[1]benzopyran-2-ones 3, which were reacted with sodium hydroxide to give the sodium benzopyranolate salt 4. Oxidative cyclization of 4 with equimolar quantities of dichlorobis(benzonitrile)palladium gave a 1:1 mixture of 2-methyl-4H-furo[3,2-c][1]benzopyran-4-ones 5 and 2H,5H-pyrano[3,2-c]-[1]benzopyran-5-ones 6, in 88-90% combined yield.