Synthesis of 4-Chloroisocoumarins via Intramolecular Halolactonization of o-Alkynylbenzoates: PhICl2-Mediated C-O/C-Cl Bond Formation.

A series of 4-chloroisocoumarins were conveniently synthesized from o-alkynylbenzoates via PhICl2-mediated intramolecular cyclization under metal-free conditions. PhICl2 plays the role of both the oxidant and the chlorine source to enable oxidative C-O bond formation and introduction of the chlorine atom. The utility and practicability of this protocol have been exemplified by virtue of mild reaction conditions, high-yielding products, simplified purification, and gram-scale synthesis.