Recent advances in the synthesis of pyrrolo[1,2-a]indoles and their derivatives

The pyrrolo[1,2-a]indole unit is a privileged heterocycle found in numerous natural products and has been shown to exhibit diverse pharmacological properties. Thus, recent years have witnessed immense interest from the synthesis community on the synthesis of this scaffold. In light of the ever-increasing demand for pyrrolo[1,2-a]indoles in drug discovery, this review provides an overview of recent synthesis methods for the preparation of pyrrolo[1,2-a]indoles and their derivatives. The mechanistic pathway and stereo-electronic factors affecting the yield and selectivity of the product are briefly explained. Furthermore, we have attempted to demonstrate the utility of the developed methods in the synthesis of bioactive molecules and natural products, wherever offered.

[3+2]-Annulation of platinum-bound azomethine ylides with distal C[double bond, length as m-dash]C bonds of N-allenamides

A Pt-catalyzed, highly regioselective reaction between N-allenamides and imino-alkynes leading to pyrrolo[1,2-a]indoles is described. This represents the first example of [3+2]-annulation of Pt-bound azomethine ylides with the distal C[double bond, length as m-dash]C bond of N-allenamides. The mechanism of the reaction was established by computational studies.

A copper-catalyzed tandem reaction for the construction of coumarin fused 9H-pyrrolo[1,2-a]indoles

An efficient copper-catalyzed Friedel–Crafts alkylation/cyclization/isomerization sequence of 3-arylcarbonyl coumarins and 3-methyl indole was developed to afford a wide range of functionalized coumarin fused 9H-pyrrolo[1,2-a]indoles with a 6-6-5-5-6 pentacyclic core.