One-pot three component reaction for the synthesis of chromone-linked naphthopyrans

Heating an equimolar mixture of 6-substituted chromone-3-carbaldehydes, beta-naphthol and dimedone in AcOH produces 3,3-dimethyl-11-(4-oxo-4H-1-benzopyran-3-yl)-1,2,3,4-tetrahydronaphtho[2,1-b]-1-benzopyran-11H-1-ones, whereas under similar condition use of Meldrum's acid in place of dimedone gave 1-benzopyrano[2,3-b]naphtho[1,2-e] pyran-7aH, 13H-13-ones and 3,4-dihydro-4-(4-oxo-4H-1-benzopyran-3-yl)naphtho[2,1-b]pyran-2H-2-ones.