Tetrahydrofuran → N-[4-cyano-3-(trifluoromethyl)phenyl]-2,2,4-trimethyl-1,3-dioxolane-4-carboxamide

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In a 50 ml 3-necked flask, equipped with a magnetic stirrer, under nitrogen at −20° C., 0.3 ml of oxalyl chloride in 1 ml of tetrahydrofuran was added slowly to 0.364 g of the sodium salt of the Example 5 (compound (8), R=Na) in a mixture of 0.5 ml of triethyl amine in 5 ml of dimethylacetamide. The resulting mixture was stirred for 30 minutes at −10° C. Then, a solution of 0.372 g of 4-cyano-3-trifluoromethylaniline in 2 ml of dimethylacetamide was added dropwise and slowly. The conversion was followed by TLC analysis (eluens:ethyl acetate/heptane=2/3). After ˜1 hour at room temperature, the reaction mixture was poured into 200 ml of saturated aqueous NaHCO3 solution, and was subsequently extracted with 2×30 ml of ethyl acetate. The combined organic layers were washed with 50 ml of brine, dried (Na2SO4) and concentrated at reduced pressure to give a dark-brown oil, which was purified by column chromatography (Merck 60 SiO2, eluens ethyl acetate/heptane=2/3). Isolated yield: 0.336 g light brown clear oil (51%). 1H-NMR confirmed the structure.

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