9H-Xanthen-9-ones from 4H-1-benzopyran-4-ones

Organic Chemistry Laboratory, Department of Biochemistry, Calcutta University, Calcutta-700 019, India Manuscript received 12 August 1999 An account of the synthesis of 9H-xanthen-9-ones (xanthones) by incorporating 1-4 carbon components into the appropriate 4H-1-benzopyran-4-ones (chromones) mainly through either a proper cycloaddition or Michael Initiated Ring Closure reaction as well as by [6+0)cyclisation of the appropriately substituted chromones is presented