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The golden ring: A synthetic approach to benzo[b]oxepin-3(2 H)-ones by heterocyclization/Petasis–Ferrier rearrangement of 2-(prop-2-ynyloxy)benzaldehydes is reported. Uniquely, the ring formation was found to only proceed efficiently in the presence of a gold catalyst. Substitution at the position ortho to the ethereal group on the salicylaldehyde ring was shown to dramatically enhance reactivity (see graphic).
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Sze et al. (2011) studied this question.
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