Intramolecular hydrogen-bonding-assisted phosphine-catalysed [3 + 2] cyclisation of ynones with o-hydroxy/amino benzaldehydes.

A new strategy for the synthesis of functionalized tetrahydrofuran derivatives was developed via a phosphine-catalysed [3 + 2] cyclization reaction of aromatic aldehydes with 4-phenylbut-3-yn-2-one. This is the first example of intermolecular cyclization of ynones with benzaldehydes, which essentially benefited from the intramolecular hydrogen bonding. This new protocol features a broad substrate scope, mild reaction conditions, operational simplicity and easy scale-up.