Vanillin → 2-(4-Hydroxy-3-methoxy-benzylidene)-5-methyl-furan-3-one

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5-methyl-furan-3-one (2, 7.0 g g, 0.071 mol) was dissolved in dichloromethane (40 mL) and taken in a 3-necked 500 mL round bottomed flask fitted with a mechanical agitator and calcium chloride guard tube. Vanillin (3b, 9.0 g, 0.059 mol) dissolved in dichloromethane (40 mL) was added. The mixture was cooled to 0-5° C. with stirring. Tri-sec-butyl borate (15.0 g, 0.065 mol) was added and stirred for 2 h. The color of the reaction mixture turned yellow. n-Butyl amine (2 drops) was added and the reaction mixture allowed to warm to room temp. on its own and stirred at room temp. overnight. The yellow color of the reaction mixture intensified. This mixture was poured into 5% aq. acetic acid solution (120 mL) preheated to 60° C. with stirring. This was stirred for 30 min., and then allowed to settle down. The dichloromethane layer was isolated and concentrated under reduced pressure to get a red color thick liquid. Hexane (80 mL) was added to this gummy material and stirred overnight. A yellow color solid crystallized out. This was filtered, dried in vacuo at 110° C. to get pure 2-(4-hydroxy-3-methoxy-benzylidene)-5-methyl-furan-3-one (4b, 10.0 g, 61% yield) as pale yellow powder, m.p. 167.5°-170.0° C.

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