The Catalytic Synthesis of N -Aryl Indoles Featuring an Alternative Disconnection. Hydroaminoalkylation for a Telescoped Reaction Sequence.

A tricatalytic telescoped synthesis toward C3-methyl- N -aryl indoline and indole products is reported. An in situ generated tantalum(V) ureate catalyst is used for the hydroaminoalkylation of o -chlorostyrene with N -methylaniline to first make a C sp 3 ─C sp 3 bond. Subsequent nickel-catalyzed C-N coupling forms N -aryl indolines, and if desired, subsequent oxidation to N -aryl indoles can be achieved using catalytic [Cu(MeCN) 4 ]BF 4 and tert -butylperoxy-2-ethylhexyl carbonate as the terminal oxidant. This strategy highlights an alternative C-C bond disconnection for the synthesis of indoles, which is enabled by the atom-economic hydroaminoalkylation reaction. The method was streamlined using a three-step, two-pot approach to afford up to 73% overall isolated yield of variously substituted C3-methyl- N -aryl indoles.