One-pot, three-component Fischer indolisation-N-alkylation for rapid synthesis of 1,2,3-trisubstituted indoles

One-Pot Synthesis of 1,2,3-Triarylindoles through Cascade Reactions Using Calcium Carbide, Iodoarenes, and Aromatic Amines

An efficient method for the construction of 1,2,3-triarylindoles through one-pot multicomponent reactions using calcium carbide, 3 mol of iodoarenes, and aromatic amines as starting materials was described. A series of target products were obtained by the simultaneous formation of five bonds in one step. The main advantages for this protocol are the use of a convenient alkyne source, wide scope of substrates, and simple workup procedure. The method can be extended to the gram scale.

Straightforward synthesis of N-arylindoles via one-pot Fischer indolisation-indole N-arylation

A microwave-promoted, one-pot, three-component synthesis of N-arylindoles has been developed, utilising sequential Fischer indolisation then copper(i)-catalysed indole N-arylation. Novel arylation conditions were identified that use a simple and cheap catalyst/base system (Cu₂O/K₃PO₄) in an environmentally benign solvent (ethanol), with no requirement for ligands, additives or exclusion of air or water, and microwave irradiation enabled significant acceleration of this commonly sluggish process. These conditions were designed to dovetail with Fischer indolisation, and the resulting one-pot, two-step sequence is rapid (total reaction time = 40 minutes), operationally straightforward, generally high yielding and it draws upon readily available hydrazine, ketone/aldehyde and aryl iodide building blocks. This process shows broad substrate tolerance and we have demonstrated its utility in the synthesis of 18 N-arylindoles bearing varied and useful functionality.

Rhodium-catalyzed cascade C–H activation/annulation/1,6-acyl migration: direct construction of free N–H indoles under mild conditions

Rh-Catalyzed regioselective cascade C–H activation/annulation/1,6-acyl migration of N-acetanilides with alkynes via C–C/C–N/C–O bond formation is developed.