Pyrroles enol ether route

The reactions of 2-hydroxy-2-(3-indolyl)ethanoamides and of ethyl 2-hydroxy-2-(2-pyrrolyl) ethanoates with trialkyl ortho-esters follow similar routes with the initial formation of the enol ethers (295) and (297), followed by an ortho- Claisen rearrangement to give the 2,3-disubstituted indoles (296) and pyrroles (298) (79JOC1885,80TL4335). 

An approach based on samarium diiodide-promoted reactions of the iminoketone 279 with aldehydes provides access to a series of substituted or fused pyrroles bearing at least two phenyl groups, for instance, the system 280 (Equation 86) <2001T4881>. In an alternative lanthanide-catalyzed route, a series of pyrroles were constructed from imines and nitroalkenes in the presence of Sm(fPrO)3 <1999T13957>. A set of 1-dimethylaminopyrroles have also been obtained by TiCU-induced reactions between 2-acetoxypropanal hydrazones with silyl enol ethers <1995TL8007>. 

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