Construction of dihydropyran-bridged macrocycles by inverse-electron-demand Diels–Alder reaction

A variety of dihydropyran-bridged macrocyclic structures were constructed by the inverse-electron-demand Diels–Alder reaction of 2-oxo-4-aryl-but-3-enoates. Controlling of the tether length and the position of the activating substituent in the substrates would guide the reaction to the formation of four different types of polycyclic frames, namely bicyclic [n.3.1], bicyclic [n.2.2], tricyclic [n.3.1.1], and tricyclic [n.2.2.2] macrocycles. The intermolecular/intramolecular selectivity of the Diels–Alder reaction was virtually governed by the tether length. The reactions were carried out rapidly under mild conditions, and offered a practical method for creating bridged polycyclic structures with large rings from acyclic precursors.