Abstract
The cheap, nontoxic and easy-to-handle CeCl3 ×7H2 O/NaI Lewis acid promoter is optimal with regard to economic and ecological consideration
and allows for useful applications in the synthesis of heterocyclic polyfunctionalized
molecules. The procedure becomes efficient if the reaction is carried out under solvent-free
conditions and on the surface of CeCl3 ×7H2 O/NaI supported on silica gel. The simplicity of our method, especially that no precautions
need to be taken to exclude moisture or oxygen from the reaction system, permit us
to perform the Friedel-Crafts-type conjugate addition of indoles to nitroalkenes.
The success of the reaction is independent of the type of indole or nitroalkene used,
and provides 3-(2-nitroethyl)indolyl derivatives which are useful building blocks
for the synthesis of various types of 3-(2-aminoethyl)indolyl derivatives. These can
be subsequently transformed to the β-carbolines with different substituents.
Key words
addition reactions - alkaloids - heterocycles - indoles - lanthanides - Lewis acids
- natural products
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