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Furan is useful starting compound for making 1,4-dicarbonyls. It can be seen as having an enol ether on both sides of its ring: if these were hydrolysed, a 1,4-dicarbonyl would result.
In the third step, a strong interaction is seen between the carbonyl and the protonated carbonyl. Though this interaction is not quite strong enough to be called a bond, it must be recognised as having an role in this transition state.