Ethyl 5-(4,5-dimethoxy-2-nitrobenzoyl)-1H-1,2,3-triazole 4-carboxylate (Synthesis Example 2) (140 mg) and p-toluenesulfonic acid monohydrate (2 mg) were suspended in methylene chloride (2 ml) under an argon atmosphere. 4-Heptane (0.14 ml) and triethylorthoformate (0.17 ml) were added to the suspension. The mixture was stirred at room temperature for 2 hr. Further, p-toluenesulfonic acid monohydrate (4.5 mg) was added thereto. The mixture was stirred at room temperature for 2 hr. The mixture was post-treated by a conventional method and subjected to separation and purification to give ethyl 2-(4-ethoxyheptan-4-yl)-5-(4,5-dimethoxy-2-nitrobenzoyl)-2H-1,2,3-triazole-4-carboxylate (160 mg, 82%) as a yellow powder.
