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Brønsted Acid‐Catalyzed Tandem Cyclizations of Tryptamine‐Ynamides Yielding 1 H ‐Pyrrolo[2,3‐ d ]carbazole Derivatives
Author(s) -
Wang Yanshi,
Lin Jingsheng,
Wang Xiaoyu,
Wang Guanghui,
Zhang Xinhang,
Yao Bo,
Zhao Yuandong,
Yu Pengfei,
Lin Bin,
Liu Yongxiang,
Cheng Maosheng
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201705189
Subject(s) - chemistry , moiety , tryptamine , carbazole , indole test , indoline , cycloisomerization , stereochemistry , nucleophile , intramolecular force , combinatorial chemistry , hemiaminal , catalysis , ketone , organic chemistry , biochemistry
Ynamides, as versatile synthetic precursors, have attracted much attention from synthetic chemists and sparked the development of a number of methodologies for the construction of various structures. 1 H ‐Pyrrolo[2,3‐ d ]carbazole is a core scaffold of a series of monoterpene indole alkaloids found in Kopsia , Strychnos , and Aspidosperma , for example. In this study, 1 H ‐pyrrolo[2,3‐ d ]carbazole derivatives were synthesized by a Brønsted acid‐catalyzed tandem cyclization starting from tryptamine‐based ynamides. This strategy prevented Wagner–Meerwein rearrangement by instantaneous intramolecular nucleophilic trapping of the indoleninium to afford a tetracyclic indoline via an in situ‐formed enol species induced by the formation of a more stable conjugate diene moiety. The functional group tolerances were investigated by using a series of readily available substrates. A plausible mechanism has been proposed based on the evidence of the capture of the hemiaminal intermediate. Lastly, a Büchi ketone, which is the pivotal intermediate in the synthesis of the indole alkaloid vindorosine, was synthesized by utilizing our newly developed methodology.