A metal-free or metal e-waste catalysed alkyne hydration-condensation-decarboxylation cascade reaction in water gives access to (fused) carbocycles

[EN] We show here that the ester-assisted hydration of alkynyl beta-ketoesters does not require any commercial metal catalyst but just protons in water (either in solution or on a recyclable solid) or metals recycled from e-waste (typically Au) to give not the expected ketones but a variety of polymethylated carbocycle compounds (hydroindanes, decalines, cyclohexanones and fluorenes) in good yields and selectivity, after a three-to-five step cascade reaction.