2,4-Bis(4-methoxyphenyl)-1,3-dithia-2,4-diphosphetan-2,4-disulfide (24.8 mg, 0.061 mmol) was added to a toluene (1 ml) solution of 2-(4-cyano-2-cyclopropyl-5-methyl-6-phenyl-1,3-benzoxazol-7-yl)-N,N-dimethylacetamide (I-313) (20.0 mg, 0.056 mmol), followed by stirring in ah oil bath at 125° C. for 5 hours. The reaction liquid was concentrated, and the resulting residue was purified by silica gel column chromatography (eluent, n-hexane:ethyl acetate=1:1, v/v) to obtain the entitled compound (14.0 mg, 67%) as a yellow solid.
