Alkylation of Allyl Fp Complexes and Formal Cycloadditions

For an alternative synthesis of this interesting alkene, see Akiba, T. Tamura, O. Terashima, S. Org. Synth. 1996, 75, 45. 

Surmont, R. Verniest, G. de Kimpe, N. Org. Lett., 2009,10, 2920. For a related paUadium(II) catalysed cyclization with elimination of water, see Utimoto, K. Miwa, H. Nozaki, H. Tetrahedron Lett. 1981,22, 4277. 

Complexes of other metals can also catalyse this reaction, but gold is superior Hashmi, A. S. K. Frost, T. M. Bats, J. W. Org. Lett. 2001, 3, 3769. 

For a discussion of whether this is a metal carbene or a metal-stabilized carbocation or both or something in between, see Fiirstner, A. Davies, P. W. Angew. Chem., Int. Ed. 2007, 46, 3410. Similarly, an oxonium ion, may also be viewed as an oxygen-stabilized carbocation. 

Pearson, A. J. Metallo-Organic Chemistry Wiley, Chichester, 1985, pp 166-167. 

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