Dimethyl Sulfoxide → Dimethyl 1,1-difluoro-2-oxo-4,8,12-trimethyl-3,7,11-tridecatrienylphosphonate

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Reaction Steps

Combine trifluoroacetic acid anhydride (1.30 mL, 0.0096 mol) with dichloromethane (20 mL) and cool to -60° C. Add dropwise a solution of dimethylsulfoxide (1.30 mL, 0.0183 mol) in dichloromethane (2 mL) while maintaining the temperature below -55° C. After addition is complete, stir for stir for 2 minutes. Add a solution of the dimethyl 1,1-difluoro-2-hydroxy-4,8,12-trimethyl-3,7,11-tridecatrienylphosphonate (1.60 g, 0.0042 mol) prepared in example 1 in dichloromethane (4 mL) and stir for 45 minutes. Cool the reaction to -78° C. and add triethylamine (3.0 mL, 0.021 mol) dropwise. Allow the reaction to warm to ambient temperature and stir for 45 minutes. Pour the reaction into water (100 mL). Extract this mixture with diethyl ether (400 mL). Dry the organic phase over anhydrous magnesium sulfate, filter and concentrate under vacuum. Purify the residue by flash chromatography (20% ethyl acetate/hexane, Rf = 0.18) to provide the title compound (1.1 g, 69%) as an oil.

Provenance & Evidence