Sodium metal (260 mg, 11 mg atom) was dissolved in methanol (50 mL) and dimethyl [(4,5-diphenyl-2-oxazolyl)methyl]phosphonate (3.89 g, 11 mmol) added followed by methyl (3-formylphenoxy)acetate (2 g, 10 mmol). The mixture was stirred at room temperature for 20 minutes before being concentrated and diluted with 2N HCl solution. The mixture was extracted with CH2Cl2, the organic phase dried over sodium sulfate and the solvent evaported to leave a yellow oil. This was combined with the crude material from a reaction performed on 2 g of the phosphonate and 985 mg of aldehyde and chromatographed on a column of silica gel. Elution with a mixture of hexanes and diethyl ether (3:2) furnished methyl [3-[2-(4,5-diphenyl-2-oxazolyl)ethenyl]phenoxy]acetate as the diethyl ether solvate (2.92 g, 46%) after recrystallization from diethyl ether, m.p. 79°-82° C.
