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[摘要]：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 ZnCl2/POCl3, 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. |
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