Haloallenyl ketones

An example of how gold oxidation state can control the structure of the product formed has been provided recently3,10 when haloallenyl ketones were used in gold-catalysed cyclo-isomerisations to give furans (Scheme 12.2) ... 

Haloallenyl ketones cyclization gives halofuranes via two competitive pathways depending on the catalyst (Scheme 34) [194]. Thus, more oxophilic Au(III) activates the carbonyl group leading to 3-halofurans by a 1,2-halogen shifts, whereas Au(I) selectively activates the terminal double bond of the allene to form 2-halofurans. 

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