3-Indolylalkanoic acids 2 react with benzoic acid anhydride under catalysis of Et₂O - ZnCl₂ and mild conditions to furnish the 1-phenyl-substituted pyrano[3,4-b]indol-3-ones 1c, 1d, and 3a, 3b. Products 1c, 1d, and 3b may be converted into the novel functionalized carbazoles 4 and 5 by reaction with acceptor-substituted alkynes.

中文翻译：

---

1-苯基吡喃并[3,4- b ]吲哚-3-酮与炔烃的狄尔斯-阿尔德反应：新型官能化咔唑

3-吲哚基链烷酸2在Et ₂ O-ZnCl _2的催化下和温和条件下与苯甲酸酐反应，得到1-苯基取代的吡喃并[3,4- b ]吲哚-3-酮1c，1d和3a，3b。产物1c，1d和3b可通过与受体取代的炔烃反应而转化为新型的官能化咔唑4和5。