Syringaldehyde → 2-(4-Hydroxy-3,5-dimethoxy-benzylidene)-5-methyl-furan-3-one

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5-methyl-furan-3-one (2, 6.0 g g, 0.061 mol) was dissolved in dichloromethane (40 mL) and taken in a 3-necked 250 mL round bottomed flask fitted with a mechanical agitator and calcium chloride guard tube. Syringaldehyde (3c, 13.3 g, 0.073 mol) dissolved in dichloromethane (40 mL) was added. The mixture was cooled to 0-5° C. with stirring. Tri-sec-butyl borate (14.0 g, 0.061 mol) was added and stirred for 2 h. n-Butyl amine (4 drops) was added, the reaction mixture allowed to warm to room temp. on its own with stirring and stirred at room temp. overnight. The orange yellow color reaction 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 an orange yellow color thick liquid. Water (20 mL), followed by ethyl acetate (100 mL) were added to this thick gummy material and the mixture concentrated under reduced pressure in a rotary evaporator until the product crystallized out. This was filtered, dried in vacuo at 110° C. to get pure 2-(4-Hydroxy-3,5-dimethoxy-benzylidene)-5-methyl-furan-3-one (4c) (7.0 g, 44% yield) as an orange yellow powder, m.p. 187.9-189.6° C.

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