Suman Kalyan Panja

Synthesis of furocoumarins and biscoumarins by an isocyanide-induced multicomponent reaction: isocyanide as a masked amine

The three-component reaction involving chromone-3-carbaldehyde, 4-hydroxycoumarin and cyclohexyl isocyanide produces furocoumarin and biscoumarin derivatives. Formation of the latter compound seems to involve cyclohexylamine. Cyclohexyl isocyanide was found to act as a masked source of cyclohexylamine.

One-pot three component reaction involving cyclohexyl isocyanide for the synthesis of furo[3,4-b]chromenes

On stirring an equimolar mixture of 4-oxo-4H-chromene-3-carbaldehyde, ninhydrin and cyclohexyl isocyanide in CH2Cl2-MeOH (7:1) at room temperature produces 3-cyclohexylimino-1-(2-hydroxy-1,3-dioxo-2,3-dihydro-1H-inden-2-yl)-1,3-dihydro-9H-furo[3,4-b]chromen-9-one which on hydrolysis produces 1-(2-hydroxy-1,3-dioxo-2,3-dihydro-1H-inden-2-yl)-1H-furo[3,4-b]chromene-3,9-dione. The structure of the latter compound was confirmed by single crystal X-ray diffraction.

Synthesis of 3-allylchromones, homoisoflavones and bischromones from ( E )-1-(2-hydroxyphenyl)-3-( N,N -dimethylamino)prop-2-en-1-one

(E)-1-(2-Hydroxyphenyl)-3-(N,N-dimethylamino)prop-2-en-1-one reacts with allyl bromide, prenyl bromide, benzyl bromide and α,α’-dibromo-p-xylene in DMF to produce 3-allyl-, 3-prenyl-chromones, homoisoflavones and bischromones, respectively. Similar compounds were also obtained by deformylative allylation or benzylation of 3-formylchromone.

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

Heating an equimolar mixture of 6-substituted chromone-3-carbaldehydes, β-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 Meldrums 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.