- A palladium-catalyzed Barluenga cross-coupling – Reductive cyclization sequence to substituted indoles
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A short and flexible synthesis of substituted indoles employing two palladium-catalyzed reactions, a Barluenga cross-coupling of p-tosylhydrazones with 2-nitroarylhalides followed by a palladium–catalyzed, carbon monoxide–mediated reductive cyclization has been developed. A one-pot, two-step methodology was further developed, eliminating isolation and purification of the cross-coupling product. This was accomplished by utilizing the initially added 0.025 equivalents of bis(triphenylphosphine)palladium dichloride, thus serving a dual role in the cross-coupling and the reductive cyclization. It was found that addition of 1,3-bis(diphenylphosphino)propane and carbon monoxide after completion of the Barluenga reaction afforded, in most cases, significantly better overall yields.
- Rahman, S. M. Ashikur,S?derberg, Bj?rn C. G.
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- A base-modulated chemoselective synthesis of 3-cyanoindoles or 4-cyanoquinolines using a palladium-catalyzed N-heterocyclization
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A selective methodology for the synthesis of either 3-cyanoindoles or 4-cyanoquinolines via a base-modulated palladium-catalyzed reductive N-heterocyclization from a common 1-cyano-1-(2-nitrophenyl)-1-alkene precursor is described. The required starting materials were prepared either by a Kosugi-Migita-Stille coupling of 2-halo-1-nitrobenzenes with a tributyl(1-alkenyl)stannane or by a vicarious nucleophilic substitution (VNS) of nitrobenzenes followed by a Knoevenagel condensation with an aldehyde.
- Banini, Serge R.,Turner, Michael R.,Cummings, Matthew M.,S?derberg, Bj?rn C.G.
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experimental part
p. 3603 - 3611
(2011/06/21)
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