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Convenient Approaches towards the Synthesis of Novel Pyrano[2,3‐ a ]carbazoles
Author(s) -
Prabakaran Kumaresan,
Zeller Matthias,
Szalay Paul S.,
Rajendra Prasad Karam J.
Publication year - 2012
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.910
Subject(s) - chemistry , wittig reaction , trifluoroacetic acid , organic chemistry , acetylene , reaction conditions , combinatorial chemistry , catalysis
Previously not easily accessible pyrano[2,3‐ a ]carbazoles were synthesized in highly convergent syntheses avoiding multistep procedures from readily available 1‐hydroxycarbazoles. Substituted pyrano[2,3‐ a ]carbazoles were produced by three different methods by treatment of the 1‐hydroxycarbazoles with dimethyl acetylene dicarboxylate (DMAD) and triphenylphoshine, by reaction with ethyl 2‐methylacetoacetate in the presence of ZnCl 2 /POCl 3 , and by reaction with trifluoroacetic acid followed by Wittig reaction with (carbethoxymethylene) triphenylphosphorane. The article also highlights the optimization of reaction conditions and strategies to avoid formation of byproducts for all three types of reactions.