Indoles allyloxy

Kawasaki. T, Terashima, R., Sakaguchi, K.-E., Sekiguchi, H., and Sakamoto, M., A short route to reverse-prenylated pyrrolo[2,3-7>]indoles via tandem olefination and Claisen rearrangement of 2-(3,3-dimethyl-allyloxy)indol-3-ones. First total synthesis of flustramine C, Tetrahedron Lett., 37, 7525, 1996. Nasutavicus, W.A., Tobey, S.W., and Johnson, E, The cyclization of nitriles by halogen acids. Part 2. A new synthesis of substituted S/Z-azepines, J. Org. Chem., 32, 3325, 1967. 

Linton and Kozlowski have installed quaternary centers at oxindole C3 in enantioselective fashion via the Pd-catalyzed rearrangement of 2-allyloxy indoles (Scheme 2) [16]. For example, indole 7 underwent an enantioselective Meerwein-Eschenmoser-Claisen rearrangement in the presence of Pd(SbF6)2 and the chiral phosphinooxazoline ligand 8 to afford oxindole 9 in 89% yield and 89% ee. A two-point coordination of the chiral palladium catalyst to the C3 carbonyl and C2 oxygen (6-membered coordination system) has been proposed to rationalize the enantioselectivity of the transformation. Modest to good enantioselectivities were also observed for a series of bisphosphine chiral ligands. 

Cao, T., Linton, E. C., Deitch, J., Berritt, S., Kozlowski, M. C. (2012). Copper(ll)-and Palladium(ll)-catalyzed enantioselective Claisen Rearrangement of allyloxy- and propargyloxy-indoles to quaternary oxindoles and spirocyclic lactones. Journal of Organic Chemistry, 77, 11034-11055. 

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