o-Vanillin → 2-Ethenylphenol

Participants

Reaction Conditions

Reaction Steps

To a suspension of methyltriphenylphosphonium bromide (19.65 g, 55.00 mmol) in tetrahydrofuran (200 mL) cooled to 0° C. is added n-butyllithium (1.6 M in hexanes, 37.5 mL, 60.00 mmol) and the reaction mixture is allowed to stir at 0° C. for 30 min. The ylide is added via cannula to a solution of 3-methoxysalicylaldehyde (3.80 g, 25.00 mmol) in tetrahydrofuran (100 mL) and the reaction mixture is allowed to stir at room temperature for 3 hours. The reaction mixture is quenched by the addition of aqueous ammonium chloride (100 mL) and diluted with water (300 mL). The aqueous layer is separated and extracted with diethyl ether (3×200 mL). The combined organic extracts are washed with water (300 mL) and aqueous sodium chloride (300 mL), dried (magnesium sulfate), and filtered through a plug of silica (10 cm×5 cm). The solvent is removed in vacuo to give the 2-vinylphenol as a crude oil which is dissolved in tetrahydrofuran (200 mL). To the resulting solution is added (S)-2-hydroxy-3-buten-1-yl p-tosylate (7.27 g, 30.00 mmol), triphenylphosphine (7.87 g, 30.00 mmol), and diethyl azodicarboxylate (5.22 g, 30.00 mmol). The reaction mixture is allowed to stir at room temperature for 12 hours. The reaction mixture is quenched by the addition of water (200 mL). The aqueous layer is separated and extracted with ethyl acetate (2×250 mL). The combined organic extracts are washed with water (200 mL) and aqueous sodium chloride (300 mL), dried using magnesium sulfate, and the solvent is removed in vacuo to give a crude solid. Purification by flash column chromatography (silica, ethyl acetate:hexanes 4:1) provides 5.33 g (57% y, >97% ee) of (2R)-2-(2-methoxy-6-vinylphenoxy)-3-butenyl 4-methylbenzenesulfonate as a colorless oil. [α]D25=−8.06 (c 9.93 in chloroform, >97% ee); Rf=0.57 (silica, ethyl acetate:hexanes 3:7); Anal. Calcd. for C20H22O5S.0.2H2O: C, 63.57; H, 5.97. Found: C, 63.37; H, 5.66.

Provenance & Evidence