2-Allylaniline, oxidative amination

Unlike the intermolecular reaction, the intramolecular aminopalladation proceeds more easily[13,14,166], Methylindole (164) is obtained by the intramolecular exo amination of 2-allylaniline (163). If there is another olefinic bond in the same molecule, the aminopalladation product 165 undergoes intramolecular alkene insertion to give the tricyclic compound 166[178]. 2,2-Dimethyl-l,2-dihydroquinoline (168) is obtained by endo cyclization of 2-(3,3-dimethyiallyl)aniline (167). The oxidative amination proceeds smoothly... 

Intramolecular oxidative aminations of olefins have alsobeen studied, and many of these intramolecular processes were observed prior to the analogous intermolecular variants. The oxidative aminations of alkenes with arylamines and arylamine derivatives catalyzed by palladium complexes were shown by Hegedus to form indoles (Equation 16.120). These reactions were conducted with orf/io-allylaniline and ort/zo-allylaniline derivatives as substrate, Pd(NCMe)jCl2 as catalyst, and benzoquinone as oxidant. Intramolecular reactions of N-tosylated aliphatic amines were reported by Larock. ° For example, the tosylamide in Equation 16.121 imdergoes cyclization in high yield in the presence of dioxygen with Pd(OAc)j as catalyst in DMSO. A related reaction (Equation 16.122) was reported recently in toluene solvent with added pyridine. ... 

In recent years, there has been a considerable focus on the development of new reaction conditions that use only molecular oxygen as the co-oxidant and do not require DMSO solvent [19]. Considerable progress has been made through the use of palladium catalysts supported by pyridine or N-heterocyclic carbenes as ligands. For example, Stahl has demonstrated that the 2-allylaniline derivative 14 is transformed to indoline 15 in 79% yield upon treatment with 5 mol% IMesPd(TFA)2 and 10 mol% benzoic acid (Eq. (1.8)) 19d]. Stoltz has reported the conversion ofamide 16 to lactam 17 under similar reaction conditions (Eq. (1.9)) [19b]. Through elegant mechanistic studies Stahl has shown that the stereochemistry of the aminopalladation step is dependent on reaction conditions, and both syn- and antt-aminopalladation mechanistic pathways are accessible in oxidative amination reactions [20]. 

Hegedus et al. have thoroughly studied the homogeneous hydroamination of olefins in the presence of transition metal complexes. However, most of these reactions are either promoted or assisted, i.e. are stoichiometric reactions of an amine with a coordinated alkene [98-101] or, if catalytic, give rise to the oxidative hydroamination products, as for example in the cyclization of o-allylanilines to 2-alkylindoles [102, 103], i.e. are relevant to Wacker-type chemistry [104]. 

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