| SYNTHESIS |
Indoles by one-pot tandem reaction Rapid generation of new derivatives of biologically interesting compounds has been boosted by the increasing use of catalysis. A current example is a method for preparing indoles from o-chloro-substituted 1-phenyl-2-alkyl alkynes through successive steps using titanium and palladium catalysts. The method was developed by Holger Siebeneicher, Igor Bytschkov, and Sven Doye at the University of Hannover, in Germany [Angew. Chem. Int. Ed., 42, 3042 (2003)]. In the first reaction, catalyzed by [(C5H5)2Ti(CH3)2], the starting material is hydroaminated with a primary amine to form an imine. Then, in the presence of Pd2(dibenzylideneacetone)3, the imine cyclizes to an indole. The starting o-chloro-substituted 1-phenyl-2-alkyl alkynes are readily prepared from 1-chloro-2-iodobenzenes and terminal alkynes. The "clever" combination of the two reactions in a one-pot procedure "results in a new and general method for the synthesis of indoles," the researchers write |
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