Intramolecular amination Hegedus indole synthesis

While the Mori-Ban indole synthesis is catalyzed by a Pd(0) species, the Hegedus indole synthesis is catalyzed by a Pd(II) complex. In addition, the Mori-Ban indole synthesis is accomplished via a Pd-catalyzed vinylation (a Heck recation), whereas the Hegedus indole synthesis established the pyrrole ring via a Pd(II)-catalyzed amination (a Wacker-type process). Hegedus conducted the Pd-induced amination of alkenes [430] to an intramolecular version leading to indoles from o-allylanilines and o-vinylanilines [291-293, 295, 250, 251]. Three of the original examples from the work of Hegedus are shown below. 

The Hegedus indole synthesis is not only compatible with a wide range of functional groups on the aromatic ring but is also tolerable for the alkyl groups at the 2 or 3 position of the allyl side chain." Other features of this reaction include (a) general accessibility for the intramolecular amination of mono-olefin from primary amines and weakly basic... 

In 1976, Hegedus et al. described the synthesis of indoles using a Pd-assisted intramolecular amination of olefins, which tolerated a range of functionalities [8a, 114]. For example, the requisite o-allylaniline 119 was prepared in high yield by the reaction of 5-methoxy-carbonyl-2-bromoaniline with n-ally I nickel bromide. Addition of 119 to a suspension of stoichiometric PdCl2(CH3CN)2 in THF produced a yellow precipitate (the putative intermediate 121), which upon treatment with Et, N gave rise to indole 120 and deposited metallic palladium. 

Reactions via Pd(II)-Alkene Complex In 1980, Hegedus et al. reported on the synthesis of indole derivatives via a Pd-catalyzed intramolecular amination of alkenes in the presence of carbon monoxide (Scheme 40.2). This reaction follows the outersphere aminopalladation mechanism. This report can be considered the first example of today s carboamination reaction although the authors did... 

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