Piloty-Robinson indole synthesis

Much less commonly found are a few other Fischer-type variations that will be briefly mentioned. The Piloty-Robinson indole synthesis is a simple variation of the Piloty pyrrole synthesis, where the [3,3] sigmatropic event is triggered by acetic anhydride or methyl iodide (Scheme 26) [142,143]. An example is shown in equation 2 [143]. 

The Piloty-Robinson pyrrole synthesis (74JOC2575,18JCS639) may be viewed as a monocyclic equivalent of the Fischer indole synthesis. The conversion of ketazines into pyrroles under strongly acidic conditions apparently proceeds through a [3,3] sigmatropic rearrange-... 

This reaction is related to the Bucherer Carbazole Synthesis, Fischer Indole Synthesis, Graebe-Ullmann Synthesis and Piloty-Robinson Pyrrole Synthesis. 

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