通过叠氮基丙烯酸酯与芳香醛缩合可以得到 2-叠氮基-3-芳基丙烯酸酯，其加热环合生成吲哚 2-羧酸酯衍生物，一般而言只有富电子的芳环（带推电子苯环，呋喃，噻吩，吡咯）可通过该方法环合。由于反应放出氮气，在环合时一定要严格控制 2-叠氮基-3-芳基丙烯酸酯滴加速度及反应瓶敞口，否则很容易喷发出来。

1、叠氮基-3- 芳基丙烯酸酯环合合成 2- 羧酸吲哚衍生物示例

      To a soluti{attr}3187{/attr} of NaN 3 (60 g, 0.92 mol) in 240 mL of DMF was added dropwise chloro-acetic acid methyl ester 1 (75 mL, 0.86 mol) at 0 °C. After the addition, it was allowed to warm to r.t. and overnight. The reaction mixture was poured into 1.5 L of water and extracted with

ether (500 mL×3). The combined organic layer was washed with brine, dried over Na2SO4 and evaporated under reduced pressure to yield 78.4 g yellow oil azido-acetic acid methyl ester 2. Yield: 90%

       To 500 mL of methanol was added portionwise sodium (15.7 g, 0.68 mol). After the addition, it was heated to reflux for 30 min. Then a solution of 4-methoxy-benzaldehyde 3 (46.2 g, 0.34 mol) and azido-acetic acid methyl ester 2 (78 g, 0.68 g) in 100 mL of methanol was added dropwise to it. After the addition, it was stirred at 5 °C for 2 h and overnight at r.t.. Then the reaction mixture was poured into ice water and stirred for 10 min. Deposited and filtered. The solid was washed with water (50 mL×3), dried under vacuum to yield 54.3 g yellow solid 2-azido-3-(4-methoxy-phenyl)-acrylic acid methyl ester 4. Yield: 69%

     To 600 mL of xylene was slowly added dropwise a solution of compound 4 (54 g, 0.23 mol) in 400 mL of xylene at reflux. After the addition, it was reflux for 1 h and cooled to room temperature and stirred overnight. The solvent was removed under reduced pressure and the residue was recrystallized with xylene to yield 28 g white solid

6-methoxy-1H-indole-2-carboxylic acid methyl ester 5. Yield: 59%