Gold(I)-Catalyzed Synthesis of 1H‑Isochromenes.

Belonging to a greater class of biologically active molecules known as benzopyrans, 1H-isochromenes and their isomers are known to exhibit a variety of medically relevant properties. An atom economical synthesis of these valuable organic moieties has been developed utilizing a gold-(I)-catalyzed cyclization of o-alkynylbenzyl alcohols. The desired 1H-isochromenes have been isolated in good yields exclusively yielding the 6-endo-dig product for most substrates. The mechanism of this reaction has been probed providing evidence for a gold-stabilized carbocation intermediate which is responsible for this high degree of regioselectivity.