Bispyranopyran-4,5-diones (2) have been prepared by the concomitant acetylation and cyclisation of bis-4-hydroxy-6-methyl-2H-pyran-2-ones (3) using a mixture of acetic anhydride and perchloric acid. Reactions of (2c) and (2d) with ammonium acetate afforded the corresponding bibpyridopyran-4,5-diones (4) while the hydrolysis of (2c) and (2d) with 20% aqueous sodium hydroxide gave bispyran-4-ones (5a) and (5b) respectively.


M SIDDIQ ,A W KHAN ,